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MPO Canopus and PhotoRed Reference Guide Copyright 1999-2011 Bdw Publishing Table of Contents Table of Contents 3 Copyright Notice 1 System Requirements 2 Technical Support 3 International Issues 3 Credits and References 4 Asteroid Databases 6 The Minor Planet Center 6 Lowell Observatory 6 About Asteroid Numbering 6 Star Catalogs 7 MPOSC3 7 Support for Other Star Catalogs 8 USNO SA1.0/2.0 Support 8 UCAC2 Support 8 UCAC3 Support 8 Dual Support 8 Manual Conventions Converting Data from Previous Versions 9 10 The “Mighty Five” 10 Prior to Version 9.0 10 Version 9 to Version 10 10 Running the Conversion Wizard 10 Overview 11 Users Guide 11 CHM Help Files 11 Multiple Instances 12 MPO Server Application 12 © 12 StarBGone! Magnitude/Intensity Relationship (M/IR) 12 Derived Magnitudes 12 PhotoRed Reduction Methods 13 Canopus and PhotoRed 13 Main Form Pages 13 Main Menu 14 Binary Maker Support The Magnitude/Intensity Relationship 23 25 Controlling the M/IR Solution 25 A Matter of Magnitudes 25 How Does Canopus Work? 26 Configuration 27 Configuration - General Page 27 Configuration - MPC Page 32 Configuration - Catalogs Page 34 Configuration - Charting Page 36 Configuration - Photometry Page 38 Generating Quick Charts 45 Generating a Quick Chart 45 General Information 45 Generating a Chart by Orbital Elements 45 Generating a Chart by Position 46 Blinking Images 47 Astrometry Overview 49 Users Guide Tutorials 49 Astrometry/Photometry Measuring Apertures 49 What is Chart Matching? 50 Generating a Chart for Astrometry 50 The Chart Generator Form 51 Reading the FITS/SBIG Header for AutoMatching 52 Manual Astrometry 53 The Photometry Residuals Form 53 Astrometry - Changing the M/IR Solution 54 AutoMeasure (AutoMatching) 55 Astrometry Reductions Page 55 Reductions Page - Astrometry Data Table 56 Reductions Page - Object Information 57 Reductions Page - Observation Codes / Processing 58 Reductions Page - Fixed Data 59 Reductions Page - File Operation 60 Astrometry - Changing the Astrometry Solution 61 Changing the Reference Star Set 62 Creating an MPC Report 62 Locating and Measuring Other Asteroids Photometry - Overview 63 65 The Users Guide 65 Some Definitions 65 The Basic Steps 65 Photometry Tutorials 66 The Sessions Form 67 Sessions Form - Sessions Data Page 70 Sessions Form - Entering Session Data 73 Sessions Form - Observations Page 79 Sessions Form - Comparison Plots Page 81 Sessions Form – Catalog Check Page 83 The Lightcurve Wizard 85 Using the Wizard 89 The Comp Star Selector 89 Lightcurve Wizard - Remeasuring and Picking Up Later 91 Finding the Period of a Lightcurve 93 It’s Easy to Be Hard 93 Period Determination – One or Two Periods? 93 Period Search Parameters 94 Analyzing the Fourier Analysis 96 The Period vs. RMS values – The Period Spectrum 98 A Detailed Look at the Fourier Analysis Routine 99 Automatic Period Scan 99 Harmonic Order Scan 100 Refining the Search Again 101 A Final Look 102 Period Determination - The Comp Adjust Form 103 Period Determination - Manipulating Phased Data 104 Period Determination – Changing Plotting Options 105 Period Determination - Editing Data Using the Plot 105 Saving Plots 106 Pan and Zoom 106 Period Determination - Viewing the Lightcurve Data 108 Period Determination - Normalized Plots 109 Period Determination - Finding the Time of Extreme Amplitude (TOM) 110 Period Determination - TOM Calculator 111 Exchanging Canopus Photometry Data 113 Export Sets 113 Working with Export Sets 113 Exporting Data 115 Importing Export Sets 115 Importing Data from Other Programs 115 Rules for Import Fields 116 Photometry Data Management 121 Database Conversions and Internet Links 125 ASTORB - Lowell Observatory Database 125 MPCORB - Minor Planet Center Asteroid Table 125 LONEOS - Lowell Observatory LONEOS Catalog 125 User Star 126 User Elements 126 Links to Other Sites 126 ASTORB Conversion 127 Steps to Convert the ASTORB file 127 ASTORB Update 128 Steps to Convert the Files 128 MPCORB Conversion 129 Steps to Convert the Files 130 MPCORB Daily Orbit Update Import 130 Steps to Import the DOU file 131 LONEOS Conversion 131 Steps to Convert the LONEOS file 131 User Star Conversion 132 Importing Henden Sequences 133 Converting User Star Data from Other Catalogs 133 Manually Entering and Editing Data 136 Managing User Elements 137 MPO Canopus Utility Programs 141 The Orbits Utility 143 Determining Elements from Positions 143 The Orbits Page 143 Orbits - Finding an Orbit 145 Orbits - Generating Elements 146 The List of Observations 147 Orbits - Analyzing the Results 147 Orbits - Vaisala Orbits 149 The Moving Object Search Utility 151 How the MOS Works 151 Using the MOS 152 MOS - Setting the Search Parameters 152 MOS - Reviewing the Results 154 The Variable Star Search Utility 157 Users Guide Tutorial 157 Two Review Methods 157 How the VSS Works 158 There’s No Substitute for the Real Thing 159 VSS - Search Parameters 160 The Extraction Data 162 VSS - Reviewing the Results (Mean/SD Tab) 162 VSS - Reviewing the Results (Targets Tab) 164 Asteroid Browser The Browser Form Asteroid Search 167 167 171 Types of Searches 171 Search Setup 171 Sorting the Search Results 173 H/G Calculator 175 H/G Calculator – Data Input 175 H/G Calculator – Calculating H/G 177 Double Star Observations 181 How Double Stars Are Measured 181 Users Guide 181 Adding Double Stars Data 181 The Double Star Measurements Form 183 Double Stars – Generating A Report 185 JD Calculator 191 Lightcurve Ephemeris 193 Users Guide 193 Generating an Ephemeris Lightcurve 193 Star Profile 195 Image Processing 197 Scaling Images 197 Biases, Darks, and Flats 198 General Requirements 199 Working with Flat Fields 200 Image Processing - Creating a Master Dark 200 Image Processing - Creating a Master Flat 201 Image Processing - Converting Images 201 Batch Image Processing 203 Image Processing - Stacking Images 207 Image Processing - Stacking (Multi) 208 Image Processing - Editing FITS/SBIG Headers 211 Editing the Header for a Single Image 213 The User Star Form 217 LONEOS Catalog Viewer 218 The MPC Report Editor 219 PhotoRed Overview 223 The Users Guide 223 About Clear to Other Band Conversions 224 The Main Form Pages 224 To-do List Help 224 Image Processing 225 Main Menu 225 Configuration 229 Using PhotoRed 231 Using PhotoRed - The PhotoRed Philosophy 231 Using PhotoRed - Getting and Measuring Images 233 Using PhotoRed - The Measurements Page 235 The Users Guide 235 Using PhotoRed – Working with Data from Canopus 236 Using PhotoRed – Working with Observation Data 238 The Photometry Wizards 241 Users Guide 241 The PhotoRed Image List 241 Photometry Wizards - The Transforms Wizard 243 Photometry Wizards - The Differential Photometry Wizard 245 Reduction Methods First Order Extinctions and Transforms 247 248 Users Guide Tutorials 249 CI Means Color Index 249 Reductions: Transforms (Normal and 1-Filter) 251 The “Hidden” Transforms 252 Reductions: First Order - Hardie 253 Reductions: First Order - Comps 255 Reductions: Second Order 256 Reductions: Nightly Zero Points 257 Reduction Methods: Errors 258 Reductions: Color Index (Comps/Target) 259 Reductions: Comps Standard Magnitudes 260 First Order Extinction Considerations 260 Manually Entering Standard Magnitudes for Comparisons. 261 Reductions: Target Standard Magnitudes 262 Reductions: AAVSO Batch Processing 265 The AAVSO Format – Beware the Check Star 265 The Process Outline 265 The Batch Reference File Generator 267 Users Guide Tutorial 267 Defining and Running a Batch Process 270 The AAVSO Report Form 273 Observed Stars Tab 273 Observations Tab 273 Batch Edit/Delete/Archive Tab 274 Batch Editing 275 Batch Edit – Update Mags 275 Batch Delete 277 Archiving AAVSO Data 277 AAVSO Reporting Tab 278 Extended Reports Tab 280 FITS Keywords 283 Copyright Notice The MPODVD, including programs, original data files, and documentation, is copyright 1993-2011 by Bdw Publishing and Brian D. Warner. Unauthorized distribution by, in, or on any media is prohibited. Trademarks are the property of their respective companies. Disclaimer of Warranty and Limited Liability All software and reference material is provided "as-is", without any warranty as to its performance or fitness for any particular purpose. Further, Bdw Publishing does not warrant, guarantee, or make any claims in regards to the correctness, accuracy, reliability, or otherwise of the software. These are the only warranties of any kind, either expressed or implied that are made by Bdw Publishing regarding any software it produces and sells. The MPO CD and accompanying manuals are copyright © 1993-2011 by Bdw Publishing. All Rights Reserved. No part of the data or information contained in any file on the CD nor any part of this manual may be duplicated or retransmitted by any means without the express written consent of Bdw Publishing. UCAC3 Copyright Notice The UCAC3 Catalog (Third U.S. Naval Observatory CCD Astrograph Catalog) supplied on a separate DVD with the MPO software is an original or direct copy of the original double-sided DVD as supplied by the United States Naval Observatory (http://www.usno.navy.mil) © June 2009 by USNO. See the README_UA3 file on the DVD for copyright and attribution information. 1 System Requirements Screen and Color Settings All MPO programs are optimized for screen resolutions of at least 800x600 at 256 colors and using the Small Fonts settings. Higher screen and color resolutions will enhance use of the programs. Using Large Fonts at 800x600 or any size font at 640x480 will make some windows larger than the screen can display. For some windows, the size cannot be changed; this is deliberate in order to maintain some continuity of display. If at all possible, use at least a 1024x768x64K setting when running the MPO suite of programs. This allows the best display of 16-bit CCD images. A setting of 256 colors sometimes does not allow the proper gray scale palette to be used for display. The programs run under Microsoft Windows 98/ME/NT/2000/XP/Vista/Win7 (32/64-bit) Minimum required system required: IBM compatible computer (486, Pentium) Microsoft Windows 98 800x600x256 screen resolution DVD 256 MB RAM Minimum system recommended: Pentium IV or equivalent @ 2GHz or higher Microsoft Windows XP 1024x786x64K or higher screen resolution DVD 512 MB RAM Disc Space Requirements The hard drive space requirements depend on which programs and catalogs you install. The core programs and supporting files (if all are installed) require approximately 70 MB. The documentation files, not including help (CHM) files, require approximately 17 MB. The common data files require approximately 180 MB. These are installed even if only one program is installed. The MPO Asteroid Viewing Guide has a set of files unique to its operation that are installed only if the AVG is installed. These files require about 200 MB. This is a minimum since the oppositions file included data for only the first 25000 numbered asteroids. The Viewing Guide will add to this file when you generate data for objects not already in the list. If you were to generate data for all the asteroids in the MPCORB file as of November 1, 2007, the total space requirement for the MPO AVG files rises to approximately 1GB The UCAC3 catalog requires approximately 7.9 GB The MPOSC3 catalog requires approximately 2.5 GB The Henden Charts require approximately 17 MB The example images require approximately 400 MB. Tutorials A second DVD includes video tutorials that mostly replace the Users Guide. The Guide is now an index to the tutorials with time stamps for “chapters” within each tutorial. 2 Technical Support Mailing Address Bdw Publishing 17995 Bakers Farm Rd. Colorado Springs, CO 80908 E-mail [email protected] Internet http://www.MinorPlanetObserver.com Yahoo Group http://groups.yahoo.com/group/MPOSoftware/ The preferred method for technical support is to visit the Yahoo support group first and post your questions there. This allows you to draw on the experience and expertise of many others. The group is monitored by Bdw Publishing almost constantly and messages will be answered as quickly as possible. Should you feel the need for private communications or be asked to send files, use the email address given above. On rare occasions, outgoing phone support will be provided by Bdw Publishing. Incoming phone technical support is not available. The web site provides e-mail links to MPO, links to the Minor Planet Center, and information on asteroids reaching opposition or of particular interest in a given month. International Issues Every effort has been made to make the presentation of existing data and entry of new data follow the formats dictated by your Windows Regional settings. However, in some cases, e.g., generating reports for the Minor Planet Center and AAVSO, the data are forced to a specific format. Among other things, this usually means using a period for the decimal character. ANSI Dates All MPO Software have been changed to require ANSI date format for input, i.e., yyyy/mm/dd. Some reports will use the Windows date format, with the requirement that leading zeros be used for dates and months < 10 and four digits in the year. Time Time format is always 24-hour format, e.g., 1:25pm displays as 13:25. Leading zeros are displayed and must be entered, e.g., you must enter '09' and not ' 9'. In most cases, the colon (:) is used as the time separator. Numbers The decimal separator in the Regional settings is used when decimal values are required, e.g., if the decimal separator is a comma (,), then the display would be something like 4,567 (a number between 4 and 5). Accented Characters Because there is no guarantee as to which fonts are on a given machine, all the MPO programs used the standard fonts shipped with Windows, i.e., Arial, System, Times Roman, and Courier New. Only those extended characters supported by the current font can be used. 3 Credits and References Lowell Observatory ASTORB Database Dr. Edward Bowell, Lowell Observatory, Flagstaff, AZ. The research and computing needed to generate ASTORB were funded principally by NASA grant NAGW-1470, and in part by the Lowell Observatory endowment. MPC Orbital Elements This contains published elements for all numbered and unnumbered multi-opposition minor planets for which it is possible to make reasonable predictions. It also includes published elements for recent one-opposition minor planets and is intended to be complete through the last issued Daily Orbit Update MPEC. As such it is intended to be of primary interest to observers. Credit to the individual orbit computers is implicit by the inclusion of the name of the orbit computer on each orbit record. Information on how to obtain updated copies of the data file must be provided. New versions of this file, updated on a daily basis, will be available at http://www.minorplanetcenter.net/iau/MPCORB.html The elements contained within MPCORB are divided into three sections, separated by blank lines. The first section contains the numbered objects, the second section contains the unnumbered objects with perturbed orbit solutions and the third contains the recent 1-opposition objects with unperturbed orbit solutions. Each object's elements are stored in a single line, the format of which is described at http://www.minorplanetcenter.net/iau/MPC_Documentation.html MPOSC3 – 2MASS Catalog The MPOSC3 catalog makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. Fourier Analysis of Lightcurve Data Dr. Alan W. Harris, Jet Propulsion Laboratory, Pasadena, CA. The routine is a direct conversion of Dr. Harris' program, used by many professionals to determine the period of a lightcurve. It uses Fourier Analysis, finding the period by least squares solution. The Determination of Orbits A. D. Dubyago; Translators: R.D. Burke, G. Gordon, L.N. Rowell, F.T. Smith - The RAND Corporation. The MacMillan Company, New York, 1961. This is an excellent reference since it both explains the theory and provides worked examples (though there are some errata of which you must be careful). Methods of Orbit Determination for the Micro Computer Dan Boulet, Willmann-Bell, Richmond, VA, 1991 A great resource with complete program listings in BASIC and worked examples. Highly recommended as it is more up-to-date than Dubyago's work and can be easily applied to desktop computers. 4 Astronomical Algorithms Jean Meeus (1991), Willmann-Bell, Richmond, VA 23235. Provided algorithms for finding accurate positions of Sun, Moon, and planets, precession of coordinates, etc. SExtractor Bertin E. and Arnouts S., 1996, A&AS 117,393 This program is the industry standard for extracting star data from FITS images. A Windows/DOS program supplied by the author is used by Canopus to implement the SExtractor routines. A Practical Guide to Lightcurve Photometry and Analysis. Brian D. Warner (2006), Springer Science+Business Media, Inc. This book gives the information you need to start an observing program for asteroid and/or variable star lightcurve work. This includes the equipment needed, how to take and measure images, and how to analyze the resulting data. Astronomical Photometry: A Text and Handbook for the Advanced Amateur and Professional Astronomer. Arne A. Henden and Ronald H. Kaitchuck (1990), Willmann-Bell, Richmond, VA 23235. This is “the Bible” for many amateur photometrists. Although the current version does not cover CCD photometry, its discussion of photometric considerations and reductions is one of the best available. A CCD specific version is planned “Photoelectric Reductions” Robert H. Hardie. Section in Astronomical Techniques, ed. W.A. Hiltner (1962), University of Chicago Press. Chicago. For many years, this was the standard on the topic of reductions and includes information still useful despite its age. StarBGone! StarBGone! was developed by making reference to a number of sources: Alard, C., Lupton, Robert H., A Method for Optimal Image Subtraction, 1998, ApJ 503, 325-331. Gary, Bruce L., Healy, David, Image Subtraction Procedure for Observing Faint Asteroids, 2006, Minor Planet Bulletin 33, 16-18. Harris, A.W., private communications, 2003, 2005, 2006 Menke, John, Asteroid Photometry: A Tricky Business (StarZap), 2005, Proceedings for the 24th Annual Conference of the Society for Astronomical Sciences, ed. Warner B.D. et al, Society for Astronomical Sciences. Pravec, P., private communications, 2005, 2006 5 Asteroid Databases The Minor Planet Center The central clearinghouse for information about asteroids is the Minor Planet Center (MPC). It accepts observations from around the world, both amateur and professional, and calculates orbits of new asteroids, updates orbits of known asteroids, and assigns discovery credits. More information including how to get an observatory number assigned can be found at: http://www.minorplanetcenter.net/ Lowell Observatory The Lowell Observatory in Flagstaff, AZ, is one of the leading solar system research facilities in the world. It runs the LONEOS (Lowell Near Earth Object Survey), one of the primary search programs for finding asteroids that may pose a threat to earth. The observatory provides a wealth of observing information for those interested in asteroids, including a database of asteroid orbital elements – ASTORB. Visit their web site at http://www.lowell.edu About Asteroid Numbering Asteroids that have no MPC-assigned number are given a number of 0. Given the rapid growth of discovery so far and even more so to come, using arbitrary numbers was no longer practical. The programs have been modified to allow search by (and use automatically where possible) name. Revised MPC Format As of this writing, the Minor Planet Center has proposed but not adopted a new format for reporting observations. Among the changes is an expanded format for designations and observatory codes to accommodate the rapidly growing asteroid and astrometric communities. MPO Canopus is able to switch to this format when the time comes, including not only the MPC reports but the conversion programs as well. By default, Canopus uses the “old” (current) format. You must specifically instruct Canopus to use the new format. 6 Do not use the new format unless and until the Minor Planet Center indicates that observers should use it in lieu of the old formatting. Star Catalogs MPOSC3 An entirely new base catalog was introduced starting with version 10. This catalog is based primarily on one provided by Lowell Observatory and is a hybrid of the Sloan Digital Sky Survey (SDSS) and Carlsberg Meridian Catalog. The MPOSC3 contains approximately 150 M stars. Most important of all is that the magnitudes in the catalog are more internally consistent than in previous versions. The catalog now includes, when available, Sloan Digital Sky Survey (SDSS) g’r’i’ magnitudes in addition to BVRI. The BVRI magnitudes were derived one of two ways: 1. Using conversion formula for SDSS to BVRI. These were used only when g’ and r’ magnitudes were available since the conversion required the g’-r’ color index. 2. Conversion formula using 2MASS to BVRI developed by Warner (Minor Planet Bulletin 34, 113-119). The table below gives the approximate errors from this set of conversions. B V R I ±0.08 mag ±0.05 mag ±0.04 mag ±0.03 mag B-V ±0.047 mag V-R ±0.021 mag V-I ±0.032 mag Astrometric Accuracy The positions in MPOSC3 are taken from the 2MASS catalog. These are recent epoch (~2000) positions and so errors due to proper motions are minimal. The catalog does not include proper motion data and so the errors will build over time but, for all but a small number of cases, only very slowly. If accurate astrometry that includes proper motions is required, use one of the UCAC catalogs. Credits MPOSC3 makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web Site is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington. 7 Support for Other Star Catalogs USNO SA1.0/2.0 Support All charting routines throughout the MPO Suite support the USNO S and A1.0/2.0 CDs. The S version is a single CD that features more than 54 million stars in the range of 15-19th magnitude. The A series is 10 (version 1) or 11 (version 2) CDs and has more than 500 million stars. The positions are much more reliable than those in the Hubble Guide Star Catalog (but still without proper motion). If using the A series and you have not copied the contents of the CDs to the root of a hard drive on your machine (or one on the network), the programs prompt you to insert another CD if the correct one is not available. Alternately, you can copy the CD(s) to a hard drive. You can copy the files to the root of a hard drive or to a directory off the root. Regardless of which option you chose, you must copy all the files from all the CDs to the same directory. Check the USNO web site at http://www.unso.navy.mil for the availability of the USNO CDs. Use of the USNO for astrometry or photometry is discouraged. The UCAC catalogs are much better for astrometry and MPOSC3 catalog provides much more stable and consistent photometry. UCAC2 Support The MPO programs support the UCAC2 (U.S. Naval Observatory CCD Astrograph Catalog) when using the original data from the CDs supplied by USNO. The UCAC catalog has much higher precision positions as well as proper motions, which are included in the calculation of positions for use in the MPO programs. The photometric quality of the catalog is higher but not on a standard system. See the README and other documentation included on the UCAC CDs for credit and copyright information. UCAC3 Support The UCAC3 catalog is supported by MPO software. A separate double-sided DVD from the USNO, or a copy, is provided with MPO software. The catalog requires nearly 8 GB of disc space but its advantage is that it provides full-sky coverage whereas the UCAC2 covered only up to about +50° Declination. Dual Support MPO Software continues to support both UCAC2 and UCAC3. However, it is recommended that you use one or the other and, if disc space is a bit of a premium, that you install only one of the two catalogs. 8 Manual Conventions The following conventions are used in this manual Click This means to depress and release the left mouse button quickly Right-click This means to depress and release the right mouse button quickly Ctrl+Click This means to hold down the Ctrl key and, while doing so, click the left mouse button Shift+Click This means to hold down the Shift key and, while doing so, click the left mouse button. Drag When referring to dragging a list of items (also called drag and drop), this means to depress the left mouse button and, while still depressed, move the mouse cursor to a specific location and then release the mouse button. Multi-select list box This is a standard Windows control that allows selecting one or more items from the list. To select one item, click on it. To select a contiguous set of items, click on the first item and then Shift+Click on the last item. All items between the first and last as well as those two are selected. To select non-contiguous items, click on the first item and then Ctrl+Click on the other items to be selected. When path names are given to files in the MPO directory tree, the presumption is that the MPO files were placed under the \MPO directory. If you installed under a different base directory name, use that name instead of \MPO. When values are given surrounded by quotes, e.g., “03”, the quotes should not be considered part of the value unless specifically stated otherwise. 9 Converting Data from Previous Versions Many changes have been made to the data tables since Canopus was first written. In order to be able to use files from all versions, you may need to convert existing data files. The “Mighty Five” This is not the five famous Russian composers but the five critical user files in the MPO v9/10 data system. PHSESS PHOBS AAVSO AAVSO2 DOUBLESTARMEASUREMENTS Canopus photometry sessions Canopus sessions observations PhotoRed AAVSO reports PhotoRed AAVSO reports, auxiliary data Double star observations The PHSESS and PHOBS files require special attention if you are installing over an existing version or using restored files from prior to v10 since the fields they store have changed over time. Those using Canopus/PhotoRed prior to version 9.4 may have used the QUICKMAGS file. This is no longer used nor supported. There is no conversion to the AAVSO files since many fields required in the AAVSO tables were not stored in the QUICKMAGS table. It is strongly recommended that you make backups of these files before running any installation and/or conversion program. Quiz: Who were the five Russian composers? Bonus points: who should have been the sixth composer but was considered “too Western?” Prior to Version 9.0 A new database engine was introduced starting with version 9. All user data files from these older versions will require two levels of conversion. First, is basic conversion to version 10 file format and, second is to include data fields new to version 10. The Double stars file was not in versions prior to 9.0 and it did not change for version 10, so there is no conversion required. Version 9 to Version 10 Some data fields were added in version 9.4 and even more in version 10.0 and so the 9.x files need converting. Canopus automatically converts the SESS/OBS and AAVSO files from 9.x to 10.0 as they are loaded. Therefore it is not required to run the Convert10 program before trying to load them. However, if you have a large number of SESS/OBS files (each pair forms what is called an export set), you can convert them all with a single run of the Convert10 program. Some other files also require conversion, these are PhotoRed observations (OBS), MPO Connections scripts (CSI), and the UserStar table (which added fields for three SDSS bands). Running the Conversion Wizard To help make conversions easier, a conversion wizard is available starting with v10. This wizard guides you through the process by asking questions and storing your answers so that all it takes is one click of a button to get things done. See the Installation Guide for additional details on the wizard and its on-line help. 10 Overview MPO Canopus/PhotoRed is a complete package for astrometry and photometry. With it you can easily measure the positions of asteroids or other targets and perform photometry on just about any variable object. Combined with the supplemental program, PhotoRed (PHOTOmetric REDuctions), you can transform raw instrumental magnitudes taken through one or more filters to standard magnitudes. This makes combing your data from night-to-night and/or with that from other observers much easier. Canopus can also provide standardized magnitudes directly, but these are not corrected for color differences between the comparisons and target. The screen shot above shows the main screen of Canopus after the program has automatically measured an image. The numbers on the chart (left) indicate reference stars while the concentric circles on the image indicate the measuring apertures for the same stars and asteroid. Depending on your computer and the number of stars in the image, the process usually takes less 2-3 seconds. This is only the beginning of how Canopus can make working with your images for astrometry and photometry fast and easy. The following section gives a brief overview of the features and use of Canopus. The rest of the manual provides details on the correct use of the features. Users Guide The Users Guide, a PDF found in \MPO\DOCS, contains many step-by-step lessons that take you through the fundamentals of MPO Canopus and PhotoRed. Don’t overlook this valuable resource! With the expanded (and expanding) Users Guide, the Reference Guide has been trimmed to include only information regarding data input and basic processing. The Users Guide has taken over the role of explaining the operation of the program. CHM Help Files Compiled HTML Help files (CHM) are now used by MPO software. The conversion was made to make programs compatible with Windows Vista®, which no longer supports old-style HLP files. You can download a file from the Microsoft web site that allows Vista to use HLP files but it was thought better to convert the help file system to CHM and remove that burden from the user. 11 Multiple Instances You can run multiple instances of MPO Canopus on the same computer. MPO Server Application The MPO programs run under what’s called “client-server” mode. The programs are the clients and a separate program, the MPO Server, is the server. It is the server that directly access data tables. This avoids data crashes since only one application is actually touching the files. For the most part, you will not have to worry about the MPO Server. It is automatically started anytime you start an MPO program and stays running in the background until you shut down the computer. The Users Guide contains a tutorial that explains how to start and stop the server. This is rarely necessary but you should know how to do it and be aware of messages or symptoms you’ll see should you need to recycle the server. StarBGone!© StarBGone! is a special feature of Canopus that subtracts selected stars from an image just before it is measured. This feature is designed specifically for those working moving targets, such as asteroids, that cross over field stars during a night's run. Without StarBGone!, those images where the target and star merged would have to be skipped, thus losing important data. StarBGone! setup is part of the Lightcurve Wizard and mage List. You do not have to pre-process your images (unless it’s darks and flats when you don't have Canopus merge those on-the-fly). The Users Guide tutorial on measuring images to generate a lightcurve also covers StarBGone! setup. StarBGone! is not a cure-all that will fix every problem. Notably, it cannot correct situations where a star several magnitudes brighter than the target is involved, especially if the star is near saturation or in the nonlinear portion of the CCD response. On the other hand, StarBGone! can do wonders in many cases. In one test, where the asteroid crossed almost directly over a star, without StarBGone!, the combined magnitude increased by 1.2mag. The same images using StarBGone showed a 0.02mag variation. Magnitude/Intensity Relationship (M/IR) When you match an image to a chart (built from stars in a catalog), Canopus finds the average difference between the instrumental and catalog magnitudes for up to 75 stars. This is the M/IR “offset”. In a perfect world, applying this offset to any star in the matched image will yield an accurate standard magnitude. However, this is the real world. For one, there is no compensation for each comparison not being the same color. Your system response is very likely not “flat” across a broad range of colors. Another is that the catalog values have errors to one degree or another. So, applying the average offset does not always yield perfect results. However, it is often “good enough” to make valid magnitude estimates and even use for analysis. You must AutoMatch each image before trying to find the magnitude of an object on the image. Different values for extinction and passing clouds will result in a different offset value for each image. Derived Magnitudes A new, significant feature in version 10 of Canopus is DerivedMags. A derived magnitude is the result of taking the difference between the instrumental magnitude between the target and a comparison and then adding the catalog magnitude of the comparison. For example, assuming using V magnitudes: Vtarget = vtarget – vcomparison + Vcomparison where lower case ‘v’ is the instrumental magnitude and upper case ‘V’ is the standard or catalog magnitude. This way you still get the benefits of differential photometry, which overcomes many sins due to changing conditions during the night, and immediate conversion to a catalog-based magnitude. 12 When using several comparison stars, a separate derived magnitude is computed for each target-comparison pair and the mean of those derived values becomes the derived magnitude for the comparison. If using a catalog with internally consistent magnitudes, the scatter in the results should be very small. It also means that linking sessions from multiple nights and users (if everyone is using the same catalog) should be relatively easy and require almost no “tweaking” of zero points to get the entire data set to merge correctly. Transforms On-the-fly Canopus allows applying color index and second order extinction corrections to the Instrumental and DerivedMags as the data are read into the period analysis engine. The AutoSave options in the configuration allow this transformed data to be saved automatically every time you do a period search. The transforms are determined using PhotoRed. The color corrections are applied to the raw data as the data are read into the period analysis engine. The original data are not color-corrected, i.e., the transforms are not applied when measuring images. This allows you to change the color indices or transforms at a later time and compute revised color-corrected magnitudes. PhotoRed Reduction Methods PhotoRed is a utility program built within Canopus that allows you to determine the transforms for your sys- tem (its response versus color), the amount of extinction on a given night, and most important, measure hundreds of images automatically for reporting to the AAVSO. The Users Guide contains several tutorials covering PhotoRed in detail. Canopus and PhotoRed Because of the ability to apply transforms on-the-fly, it is no longer required to import Canopus data into PhotoRed to get calibrated magnitudes for the target. The process of working between the two is relatively easy and will be easier still when the AAVSO APASS catalog becomes available. This catalog will provide magnitudes in BVr’g’i’ to about 0.02 mag internal consistency and accuracy from mag 10-17 over the entire sky. It will be like having secondary standards in every field. This will further reduce the need for some of the routines in PhotoRed. AAVSO Batch processing will remain a function of PhotoRed, as will the methods for finding your system transforms and second order extinction terms. Main Form Pages The Canopus main form has nine pages. You can go to a given page by clicking the appropriate speed button on the main toolbar, Pages on the main menu, or using the keyboard. Measurement Page (Ctrl+1) This page is where you load images to be measured, generate the matching chart (or let Canopus generate it with the AutoMatching feature), measure the comparisons and/or target, and set the reference stars. Blinker Page (Ctrl+2) Use this page to “blink” two or more images to find a moving target. Reductions Page (Ctrl+3) This page displays the astrometric data after measuring an image. This includes the calculated position of the target, the stars used in the solution as well as the residuals from catalog positions for each star and the standard deviation of the solution in RA and Declination. 13 Period Search Page (Ctrl+4) This page allows you to select the data from one or more sessions for a given target to be used in a period search using Fourier analysis. You can set the initial search parameters and the program displays plotted data in raw (mag. versus date) or phased (mag. versus phase) form. Normalized Plot Page (Ctrl+5) This page displays a plot of the normalized data when analyzing the lightcurve of a variable star and you've set the configuration options to produce a file compatible with Binary Maker. This plot should have the same basic shape as the lightcurve on the Period Search Page but it will be forced to have the deepest minimum at 0% and the highest maximum (~1.0) at 25% or 75%. Charts Page (Ctrl+6) Use this page to generate finder charts for use at the telescope (or computer monitor) and to generate a chart for the same area as the chart on the Measurements Page. The latter option allows you to locate stars and review their data without disturbing the data and settings on the Measurements Page. Orbits Calculator Page (Ctrl+7) This page is used to calculate the orbital elements of a moving object using one of several methods. In particular, it comes in handy if you have a suspected new asteroid and want to do follow-up. You would generate a “Vaisala orbit” to predict where the object will be on a given date. Vaisala Page (Ctrl+8) This page is used to display the “Vaisala Box”, which is a region bounded by given RA and Declination values in which the suspected target is most likely to be found. Conversions Page (Ctrl+9) This page provides URL links to download the latest version of the MPC and Lowell asteroid data files and to some more popular astronomy sites. In addition it provides access to the programs that convert the raw data from the sites to the format used by the MPO programs. Main Menu Most of the features in Canopus are accessed via the main menu and its submenus. In some cases, you access the menu item using the keyboard by pressing a specific key combination. For example, to display the Configuration form, press Ctrl+C, meaning you should depress and hold the Ctrl key while you press the ‘C’ key and then release both. Hot Keys Hot keys, keystroke combinations, have been incorporated into the main menu to make accessing the more common features of Canopus quicker. Functions Ctrl+A AutoAstrometry Ctrl+O Open Image Forms Shift+Ctrl+B Asteroid browser Shift+Ctrl+C Open Configuration form Shift+Ctrl+D Double Star report Shift+Ctrl+E Lightcurve ephemeris generator Shift+Ctrl+H H-G Calculator 14 Shift+Ctrl+I Set Image List (Lightcurve Wizard) Shift+Ctrl+L Set Double Star list Shift+Ctrl+M Moving Object Search Shift+Ctrl+R Asteroid Search Shift+Ctrl+S Open the Sessions form Shift+Ctrl+V Variable Star Search Shift+Ctrl+W Open the Lightcurve Wizard Main Menu - File Menu Configuration This displays the Configuration form where default settings for Canopus are made and saved. See the section on Configuration starting on page 27 for details. Exit This closes Canopus and all open forms, including PhotoRed if it’s open. Use Alt+X to invoke this menu item via the keyboard. Main Menu - Image Menu Open This item opens a file open form where you can select an image to view. The image is displayed on the right-hand side of the Measure page, i.e., on the Image Panel. Image formats supported by Canopus are: File Type FITS SBIG Windows bitmap JPEG Extensions FTS, FIT SBIG, ST?, 237, 255 BMP JPG Only FITS and SBIG images can be used for AutoMatching and photometry. Close Select this to close the image in the Image Panel Save as Click to open a file save dialog that allows you save the file in the Image Panel under a different name and/or format, with some restrictions. Format FITS/SBIG BMP JPEG Can Convert To FITS/SBIG/BMP BMP JPEG Even if the image has been processed, i.e., scaled or inverted, the saved image uses the original data. If you want to save a copy of the processed image, use the “Save processed bitmap” menu item. Save processed bitmap Click to save the processed image in the Image Panel to either a Windows bitmap (BMP) or PNG file. Whenever an image is altered in Canopus, i.e., scaled or inverted, only the display image is altered. The original image data are not changed. You can save the processed bitmap (BMP) using this option. 15 You can also save the processed bitmap by right-clicking over the image and selecting “Copy to clipboard” from the pop up menu. Open a graphics program and paste the copied bitmap into a new image where you can do additional processing before saving the image. Auto match/measure Use this item after you’ve loaded an image into the Image Panel and are sure that the configuration settings for the number of rows and columns, pixel size, and system focal length are correct. While the matching routine can make up for some differences, there are limits. Canopus attempts to read the FITS header for the critical configuration settings, which allows for some flexibility in the settings. The smallest room for error is the focal length setting, which should be close to the actual value and match the one stored in the header. Additional details can be found in the Configuration section. Generate manual chart Use this option to match the chart and image manually. You may need this when the program cannot AutoMatch an image. In short, you’ll select two stars on the image and match them with their counterparts on the image. From there Canopus can finish the matching on its own or allow you to pick the reference stars for astrometry and photometry yourself. Clear Astrometry Data Use this to clear the astrometry data (plate constants, etc) for the current image. Sticky invert Check this menu item to have all images inverted as they are loaded. Usually this means black stars and light background. If you uncheck the item, the current and all subsequent images revert to “normal”, usually white stars on a dark background. Load dark Select this item to display a file open dialog so you can locate a dark frame that is to be applied to all images loaded throughout the Canopus session. If an image is loaded, it overrides the default dark frame in the Configuration settings, if any. By default, the “Use dark” menu item is checked when you load a dark, meaning the dark is applied to loaded images. Don’t load a dark frame if the images you’ll be loading already have a dark frame applied. Clear dark Use this item to clear the dark frame selected by the “Load dark” menu item or the default dark specified in the Configuration settings. Use dark Check this menu item to have the image loaded by “Load dark” or the default dark frame from the Configuration settings applied to images as they are loaded. Uncheck the menu item to have images loaded without the dark frame applied. Unchecking this menu item does not clear the dark frame, as does the “Clear dark” menu item. To use the same dark frame again, check this menu item. It is not necessary to reload a dark frame unless the images to be loaded require a different dark frame. Load flat Select this item to display a file open dialog so you can locate a flat frame that is to be applied to all images loaded throughout the Canopus session. If an image is loaded, it overrides the default flat frame in the Configuration settings, if any. 16 By default, the Use flat menu item is checked when you load a flat, meaning the flat is applied to loaded images. Don’t load a flat frame if the images you’ll be loading already have a flat frame applied. Clear flat Use this item to clear the flat frame selected by the “Load flat” menu item or the default flat specified in the Configuration settings. Use flat Check this menu item to have the image loaded by “Load flat” or the default flat from the Configuration settings applied to images as they are loaded. Uncheck the menu item to have images loaded without the flat applied. Unchecking this menu item does not clear the flat frame, as does the “Clear flat” menu item. To use the same flat frame again, check this menu item. It is not necessary to reload a flat unless the images to be loaded require a different flat frame. Load bias Select this item to display a file open dialog so you can locate a bias frame that is to be applied to all images loaded throughout the Canopus session. Bias frames are used when the dark frame exposure does not match that of the image being loaded. Should the exposures differ, the dark frame is scaled to match the image. For this to work, the bias is subtracted from both the dark and image being loaded before the dark is scaled. This allows the natural “zeroexposure noise” to be removed before the scaling. See some of the CCD imaging books listed in the references section for a complete discussion on the use of bias frames. By default, the Use bias menu item is checked when you load a bias frame, meaning the bias frame is applied to all loaded images. Don’t load a bias frame if the images you’ll be loading have already been processed with a bias and dark frame. Clear bias Use this item to clear the bias frame selected by the “Load bias” menu item. Use bias Check this menu item to have the image loaded by “Load bias” applied to images as they are loaded. Uncheck the menu item to have images loaded without the bias applied. Unchecking this menu item does not clear the bias frame, as does the “Clear bias” menu item. To use the same bias frame again, check this menu item. It is not necessary to reload a bias unless the images to be loaded require a different bias frame. Header info This menu item displays a read-only list of the FITS or SBIG header. No information is displayed if the image format is BMP or JPEG. You can also display the header info by right-clicking over the image and selecting “Image info” from the pop-up menu. Scaling Select this item to display the image scaling form, which allows you to set the background and range values as well as invert the image. You can also display the scaling form by right-clicking over the image and selecting “Scaling” from the pop-up menu. 17 Main Menu - Photometry Menu The Photometry menu is used to manipulate the M/IR offset and standard deviation, create and manage photometry sessions, and start the process of measuring images for photometry. Residuals This menu item displays the Residuals form, which shows the stars selected for establishing the M/IR, whether or not the star is actually used in the calculations, and the difference between the catalog magnitude and the predicted magnitude based on the M/IR solution. Session Use this menu item to display the Sessions form where you can create a new session for photometry or edit data of an existing session. Load export set This menu item allows you to load previously saved data for a given target. Canopus allows you to export session information from the main session and observation files. These files (a SESS/OBS pair is called an export set) can be sent to other Canopus users so that they can merge your data with theirs. Import into export set There are two submenu items, one that allows you to import data into an export set from your main session and observations files or to import data from another observer’s export set. The purpose of both is to allow you to merge your data with that of other observers without putting “foreign” data directly into your main session and observations files. Direct import of Canopus data This feature is designed for those who work on more than one computer and want to merge data from one computer into the full database on a “master” computer. The imported data must be in an export set and cannot be text files generated by other programs. You should not use this feature to merge data from other observers into your master table. In that case, their data is your data. Instead, you should export your sessions for the target in question and work with those files. See “Working with Export Sets” and the subsequent sections starting on page 113. Import ALCDEF into empty export set ALCDEF stands for Asteroid Lightcurve Data Exchange Format. This is a proposed standard for exchanging basic lightcurve data and “metadata” (data about the data). See the Users Guide for tutorials on exporting and importing ALCDEF data and more information on the standard itself. If working with other Canopus users, export sets are the highly recommended way to exchange data. In order to support as wide a range of photometry programs as possible, the ALCDEF standard does not include all the data available in Canopus files. Store MPC/ALCDEF data in session NOTES When generating files for an ALCDEF report (visit http://www.minorplanet.info/alcdef.html and see the Users Guide), Canopus looks in the NOTES field of the sessions being included for information regarding the contact person and observatory details. This information is automatically included in the NOTES field when you create a new session. However, sessions created before this feature was implemented (pre 10.3.1), may be missing the information. Use this menu item to edit every session in the PHSESS file and include the information. The data include, from the MPC tab on the Configuration form: Contact1, Contact2, Observer, and Measurer. In addition the longitude and latitude from the General tab. 18 The presumption is that the PHSESS file includes data generate only by you and that the same values applied for all sessions. If your PHSESS file includes sessions from other observers, you should export those sessions and delete them from your PHSESS file. If your observing information changed, you can still use this feature but you will need to edit the NOTES field for those sessions where the information differs from the settings used in this operation. Clear Session This clears the current session, meaning there is no default session into which you can add observations. If you have used the Load save session(s) menu option to load data, you must use Clear Session before selecting Load save session(s) again to use a different set of data or before using the main session and observation files. It is not necessary to use this option when switching among sessions in the main files. Lightcurve Wizard Use this menu item to display the Lightcurve Wizard, which guides you through the process of selecting comparison stars and the target to be measured. In particular, the wizard can tell Canopus how to compensate for a moving target’s motion so that as each image to be measured is loaded, Canopus can automatically find the target. The Users Guide has tutorials covering the Lightcurve Wizard. Set image list This menu item displays a form where you select one or more images to be measured after first running the Lightcurve Wizard. You can set the image list at any time after running the wizard. For example, you may run the wizard after getting the first 50 images in a night’s run. If you don’t run the wizard again and don’t disturb the M/IR set before running the wizard, you can use this option to measure images taken after the first 50. Clear image list This option clears the list set by Set image list. Main Menu - Utilities Menu The Utilities menu provides access to several features within Canopus. Moving Object Search (MOS) This item displays the Moving Object Search form, which allows you to detect moving targets in your images. The search can handle any number of groups of images, with each group containing exactly three images. Canopus automatically generates an MPC compatible report and allows you review the findings by displaying the target on each image. See the MOS section starting on page 151 for more information and the tutorial on the Users Guide. Variable star search Select this item to display the Variable Star Search form. When working a target for its lightcurve, it’s entirely possible that one or more stars in the field are variable (hopefully, not one of your comparison stars!). This feature of Canopus automatically finds those potential variables using criteria you establish. When done, Canopus displays a plot of the data and the location of the target so that you can do a more formal measurement of the object if you believe it warranted. See the VSS section starting on page 157 for more information and the tutorial in the Users Guide. Asteroid Browser Select this to display a separate form that allows you to browse the MPC or Lowell asteroid data tables and to generate an ephemeris for a given asteroid. See the Search section starting on page 167 for more information. Asteroid Search Select this to display a form that lets you search for asteroids in the MPC or Lowell data tables that are above the horizon or within a certain distance of a fixed point at a given date and time. See the Search section starting on page 171 for more information. 19 H/G Calculator This displays a form that allows finding the H (absolute magnitude) and G (phase slope parameter) for an asteroid. For this, you need V magnitudes over a range as wide a range of phase angles as possible. See the H/G Calculator section starting on page 175 for more information. Double Stars This menu has two submenus. Set Double Star List Click this item to display a multi-select file open form and then select all images that you want to measure. If you select one or more files, this displays the Double Stars List form, which makes measuring double star images more efficient. Double Star report Select this to display a separate form that lets you review and generate reports for your double star observations. See the Double Star section starting on page 181 for more information and the tutorial in the Users Guide. Julian Date calculator This displays a form that computes Julian Date and Heliocentric Julian Date from a calendar date or the calendar date from Julian Date. See the Julian Date Calculator section starting on page 191 for more information. Lightcurve ephemeris This displays a form that imports the Fourier coefficients found when finding the period of a lightcurve. From these, you can generate the expected lightcurve for a given date and time. This can be useful for planning when to observe a target so that you get data for a specific part of the lightcurve. See the Lightcurve Ephemeris section starting on page 193 for more information and the tutorial in the Users Guide. Star profile This displays a form that remains visible until closed. Each time you click on a star, its intensity profile is displayed in the form. Image Processing This menu provides access to the image processing submenu. For details about image processing in Canopus see the Imaging Processing section starting on page 197. SBIG to FITS This menu item allows you to convert one or more SBIG format images to FITS. FITS to SBIG This menu item allows you to convert one or more FITS format images to the SBIG format. Edit header This menu item allows you to modify the header information in an SBIG or FITS header one file at time or to change one more values to common values in any number of images. See Use the header editor with great care. Changing some values may result in the image being no longer readable by any image program. Batch process This menu display a form that allows you select one or more raw FITS or SBIG images and have Canopus perform a number of image processing functions. A new image is created (the original is not altered) for each image selected. 20 Set file date/time Sometimes after image processing in other programs, the file date and time are changed to that when the file was last modified. This is not always desirable, i.e., it's better to keep the original file date and time. This menu option allows you to select one or more SBIG/FITS images and force the file date/time to match the midexposure date/time based on the information in the image header and the configuration settings. Get image info This menu item gets basic information for one or more images in a directory and then saves it in a text file with the data lines tab-delimited for easy import into a spread sheet program. Here is a brief example of what’s generated. Directory: E:\mpo\EXAMPLES\LTCURVES\A771\SEP18\ Image, JD, Date, Time, Exp, Object A771A001.FIT A771A002.FIT A771A003.FIT A771A004.FIT A771A005.FIT 2451439.620706 2451439.625011 2451439.629155 2451439.633310 2451439.637454 1999/09/18 1999/09/18 1999/09/18 1999/09/18 1999/09/18 02:53:48 03:00:00 03:05:58 03:11:57 03:17:55 120.00 120.00 120.00 120.00 120.00 771 771 771 771 771 User Star Management This item displays the User Star Management form where you can add new or updated data to the User Star catalog. This catalog is often used in PhotoRed, e.g., by default it contains a large number of Henden star fields for use as secondary standards. View LONEOS This item displays the LONEOS management form that allows you to view and edit the LONEOS catalog. MPC report editor This item displays the MPC report editor, which is a fixed-pitch font text editor that allows you to modify a report generated by Canopus before you send it to the Minor Planet Center. See page 219 for more information. For the next three items, see the section on photometry data management, starting on page 121. Backup Current Sessions/Observations Use this item to make a backup copy of the session and observations files in current use. Pack/Renumber Current Sessions/Observations Use this item to pack (clear empty space) and renumber the current sessions and observations files. This is handy during collaborations when you get data from a number of observers, often out of time order. Manage Sessions Lists This displays a form that shows the names of objects for which sessions lists have been stored. You can delete older lists that you're no longer using. Main Menu - Pages Menu Use the submenu items to select which page of the main form is displayed. The menu items allow keyboard shortcuts so that you switch among pages without having to use the mouse. Measurement Page Blinker Page Reductions Page Period Search Page Normalized Plot page Charts Page Orbits Calculator Page Ctrl+1 Ctrl+2 Ctrl+3 Ctrl+4 Ctrl+5 Ctrl+6 Ctrl+7 21 Vaisala Page Conversions Page Ctrl+8 Ctrl+9 Main Menu - Help Menu Contents Use this item to display the Help system. About This item displays Canopus version information Main Menu - PhotoRed Menu This is the last item on the far right of the Canopus main menu. Launch PhotoRed Select this item to start PhotoRed. This starts PhotoRed and displays it as a child program of Canopus. As a child program, the PhotoRed window has certain behavior of which you should be aware. Otherwise, there can be some confusion since PhotoRed may not always be visible. 1. Since PhotoRed is a child of Canopus, PhotoRed never shows up in the Windows task bar. 2. If you minimize Canopus, PhotoRed is also minimized. This is because it is a child of the Canopus main form. When a program is minimized, all its open windows are also hidden. 3. When you maximize Canopus while PhotoRed is open, PhotoRed is behind Canopus and so you cannot see PhotoRed. Once PhotoRed is running, this menu item is disabled. If you close PhotoRed, it is enabled. Hide PhotoRed Select the menu item to hide the PhotoRed window. This does not minimize PhotoRed but actually hides it from view. If PhotoRed is minimized so that you only see its title bar, the title bar disappears. Bring PhotoRed to Front Select the menu item to display PhotoRed in its previous size and location. If PhotoRed was minimized when you hid it, it is restored to normal state and made the uppermost window on the desktop. Show PhotoRed Transforms Select this item to display the PhotoRed transforms form where you can change the color indices of the comp stars and/or target before you apply transforms on-the-fly. Backup Current Transforms Select this item to store the current complete set of transforms (extinction, transforms, color indices, etc) to a file that can be loaded later on. This is useful if working with several systems and you want to apply transforms on-thefly. Load Saved Transforms Select this item to restore a complete set of transforms into memory and, if open, the PhotoRed transforms form. The color indices will be used when applying transforms o-the-fly. Make sure you have the correct set of transforms loaded before you start data analysis. Closing PhotoRed If you close PhotoRed, “Launch PhotoRed” is enabled. If you close Canopus, PhotoRed is also closed. 22 There are similar menu items on PhotoRed to hide and show the Canopus main form. See the PhotoRed section of the manual for more information. Binary Maker Support Binary Maker is a popular program by David Bradstreet that allows one to construct a binary star system based on lightcurve observations as simple as phase and “flux”, which is a derivative of magnitude. Canopus has been modified to generate a file that includes data compatible with Binary Maker, thus allowing you to determine the characteristics of a star that you observe. Version 2 is DOS-based while Version 3, written in Java, is compatible with several different platforms, e.g., Windows and Mac. The core files are upwards compatible, meaning that the data generated by Canopus is valid for both versions. For information about Binary Maker, contact Dr. David H. Bradstreet of Eastern College in St. Davids, Pennsylvania, Contact Software, 725 Stanbridge St., Norristown, PA 19401-5505. [email protected]. 23 24 The Magnitude/Intensity Relationship The Magnitude/Intensity Relationship (M/IR) is mentioned frequently throughout this manual and so it’s best to have an understanding of what it is, how it’s derived, and its limitations. Each time you measure the centroid of a star on the image, Canopus temporarily stores the sum of the pixel values within the measuring aperture less the background value. In a “perfect world” the difference between the instrumental magnitude of any given star and its catalog value is a constant (m-M = k for all stars). Color differences and your system’s response over a range of colors as well as errors in the catalog magnitudes mean the constant is not constant. With a good catalog and stars of a similar color, however, the standard deviation of the average m-M values is fairly small. By applying this offset to the instrumental magnitude of any star on an image, Canopus can compute a catalog-based magnitude, usually based on a standard magnitude band such as V. Each time you do an AutoMatch, where you match the image to a chart using catalog magnitudes, the MIR values are displayed in the Photometry toolbar located at the upper right of the Canopus main form. Refs is the number of stars in the solution. Offset is the average of the m-M values. SD is the standard deviation of the offset value. Controlling the M/IR Solution We’ll jump ahead a little and say that you can control the M/IR solution by using a setting in the configuration form. This setting is the maximum error between the catalog magnitude and the M/IR-derived value using the offset. If the error is greater than this setting, then the star is automatically eliminated from the M/IR solution. This reduces the number of stars in the M/IR solution but it effectively removes stars with bad catalog magnitudes, stars that were saturated or non-linear, had a hot or cold pixel, etc. A Matter of Magnitudes Canopus always records the “instrumental” magnitude of a comparison or target. This is computed directly from the sum of the ADU counts for the object and then normalized to a 1-second exposure. This means that even images with different exposure times can be directly compared among one another, assuming the same system was used. The instrumental magnitude is independent of any catalog used. It is strictly a function of the system that took the image. Canopus can also record a true magnitude (TrueMag from here on). This is based on the M/IR offset. It is available only if an image was AutoMatched before measuring it. Naturally, a true magnitude is only as “true” as the catalog value and system allow. You must AutoMatch each image independently to get an accurate set of TrueMags for an image since extinction and changing conditions affect the instrumental magnitudes and, therefore, the M/IR offset. The MPOSC3 catalog provided with MPO software includes the Carlsberg Meridian Catalog (CMC-14) as well as data from the Sloan Digital Sky Survey (SDSS). These magnitudes are mostly SDSS r’ with some g’ and i’ when available. Almost all stars in MPOSC3 also have BVRI magnitudes derived from 2MASS J-K magnitudes (see Warner, 2007, Minor Planet Bulletin 34, 113-119). These have an internal consistency of ~0.05 mag for V and 0.03 mag for R. Many tests have been run using the magnitudes from the MPOSC3 catalog, mostly to link data sets from many nights. Generally, individual sessions “fall into line” to within 0.02 mag when using a calibration method involving the Comparison Star Selector and instrumental magnitudes. “Catalog-based” magnitudes are those referenced to the magnitudes within a given catalog (or standard photometric system). This term is used instead of “absolute” to avoid confusion with the standard definition of “absolute magnitude”, which is the brightness of an object (usually a star or galaxy) when it is 10 parsecs from Earth. 25 How Does Canopus Work? There are two basic approaches in Canopus. Differential Photometry This is where the difference between a target and comparison (or average of several comparisons) using instrumental magnitudes is found for each image. It is this differential value that is used in analysis. Since, in most cases, any variations caused by external factors are the same across the entire image, this approach nullifies those factors. What remain are the internal factors, the differences in color between the object and comparison stars usually dominating things. You must take care not to use stars that are beyond the linear response of the camera, let alone that are saturated – even if it’s only one pixel out of dozens. No offset is added to the difference to obtain a “true” or “catalog” magnitude for the object. This type of photometry is called Instrumental in this Guide. Catalog-based Photometry This approach uses the M/IR to compute the magnitude of the target directly and ignores the chosen comparisons altogether. If the M/IR is computed image by image, this reduces but does not eliminate external factors. Under favorable conditions, this approach produces good catalog-based magnitudes. However, one cannot be sure if “favorable conditions” prevailed throughout a session. These will be called TrueMags in this Guide. A Hybrid Approach (Derived Magnitudes) Another approach is a hybrid of the two methods. It’s one that’s long been used by the AAVSO for submitted CCD observations. This is the recommended approach for almost all measuring for time-series photometry. It gives catalog-based values while retaining the considerable virtues of differential photometry using instrumental magnitudes. In this method, the program finds the instrumental magnitude difference between the target and a given comparison star (mt – mc) and then adds the catalog magnitude of the comparison. This results a catalog-based magnitude for the target. Put mathematically Mtarget = (Itarget – Icomparison) + Mcomparison where Mtarget Itarget Icomparison Mcomparison catalog magnitude of the target instrumental magnitude of the target instrumental magnitude of the comparison star catalog magnitude of the comparison star If you use N comparison stars, then you find N magnitudes for the target. The mean and standard deviation of that mean for the N values can be used for the final magnitude for the target. These values will be called DerivedMags in this Guide. The AAVSO Batch Processing routines in PhotoRed extend this approach to allow correcting for the color difference between the target and each comparison separately and then to output the data in special files that are used to generate reports specifically for the AAVSO. Canopus can also apply corrections on-the-fly. As will be shown later, the improvement in the standard deviation (error) can be reduced by 5-10x, depending on a number of factors. When using this approach, it is not necessary to AutoMatch every image before measuring. What is necessary is having the catalog magnitudes for the comparisons. These can be found automatically when using the Comp Star Selector (CSS) in the Lightcurve Wizard and further improved by using routines in PhotoRed to help. 26 Using the CSS and Wizard are covered in depth in the Users Guide photometry tutorials. Configuration This form is used to set a number of default values used by Canopus. You are able to save multiple “profiles” under different names. This comes in handy if you are measuring images taken with different telescope/camera combinations. It is is accessed by selecting File | Configuration from the main menu, clicking the configuration speed button on the main tool bar, or entering Shift+Ctrl+C from the keyboard. Configuration - General Page Profile To select an existing profile, chose an item from the drop down list of the combo box. To create a new profile, enter the new name in the edit box of the comb box and then set the configuration values as needed. To delete an existing profile, select the profile from the drop down box and then click the Delete button. Click <OK> to save the profile and have its name displayed in the caption bar of the main Canopus form. This helps keep track of which profile is being used when running more than one instance of the program. Click the <To Text> button to save the configuration settings in a text file. The main reason for this feature is to help tech support with issues such as AutoMatching images. Longitude Enter the longitude from where the images to be measured were taken. The three entry controls from left to right are for degrees, minutes, and seconds respectively. Check the “W” box if the longitude is west. Latitude Enter the latitude from where the images to be measured were taken. The three entry controls from left to right are for degrees, minutes, and seconds respectively. Check the “N” box if the latitude is north. Elevation Enter the elevation above sea level, in meters, from where the images to be measured were taken. 1 foot = 0.3048 m; 1 meter = 3.281 ft. UT Offset Enter the time, in hours, minutes, and seconds (HH:MM:SS) that the time in the SBIG/FITS headers differ from Universal Time. Use leading zeros to fill all positions in the field. Some examples: 27 Header Time = UT Header Time = Mountain Standard Header Time = Mountain DST Offset = 00:00:00 Offset = 07:00:00 Offset = 06:00:00 This setting has nothing to do with your computer clock and the regional settings in Windows. It is the offset of the time in the image headers from UT. Most acquisition software stores dates/times in the header as UT and so you would enter 00:00. You need to confirm this if you're not certain. Behind UT Check this box if the image header UT offset is behind UT. Uncheck the box if the image header UT offset is ahead of UT. In general, if the time in the header is not UT, then check this box if you are in the Western Hemisphere and do not check the box if you are in the Eastern Hemisphere. If the UT Offset is 0, the setting of this box makes no difference. F.L. Enter the actual focal length of the system in inches (or millimeters), and not the value computed using the f/ ratio. This is particularly important when using focal reducers, which may not always reduce to the stated f/ ratio. It’s important this value be within about 30% of the true value since the AutoMatching feature, which matches images to star charts, is sensitive to this setting. See “Automatic Override of Image Settings” on pg. 29 for important information about this setting. In./mm Check the appropriate radio button to indicate if the focal length is in inches or millimeters. It is very important that you have these set correctly. Internally, Canopus assumes inches and so, if the “mm” button is checked, the value in the focal length field is divided by 25.4. It is this “corrected” value that is passed to other elements inside the program. e/ADU Enter the conversion value given in your camera manual that transforms the number of electrons per Analog-toDigital units. This value is used to compute the Signal-to-Noise ratio. This value is not critical to most operations, so use 2.3 if you don't know the value. The e/ADU is used when computing the instrumental magnitude of an object. If you have the wrong value, then the instrumental magnitude is incorrect but by a constant value for all magnitudes, i.e., a vertical shift in a plot of true versus computed instrumental. When the instrumental magnitudes are used in PhotoRed to reduce to a standard system, the errors automatically drop out. The M/IR solution also auto-corrects by just finding a different offset from catalog values. For the next four settings, also see “Automatic Override of Image Settings” on pg. 29 for important information. Col (pix) Enter the effective number of pixels per row (the number of columns) in the images to be measured. If the images were taken at 1x1 binning, this value is the same as the physical number of pixels per row on the chip. If taken at 2x2 binning, you would enter a value that is one-half the physical number of pixels. Typical examples for 1x1 binning: Size (m) Enter the effective horizontal size of the pixels, in microns or arc seconds, in the images to be measured. Note this is different from the physical size of the pixels on the chip if you the images were taken at other than 1x1 binning. If the images were taken at 2x2 binning, you would enter a value double those shown above and triple the values if shooting at 3x3 binning. 28 Rows (pix) Enter the effective number of pixels per column (the number of rows) in the images to be measured. If the images were taken at 1x1 binning, this value is the same as the physical number of pixels per column on the chip. If taken at 2x2 binning, you would enter a value that is one-half the physical number of pixels. Size (m) Enter the effective vertical size of the pixels, in microns or arcseconds, in the images to be measured. If entering the size as pixels, this is different from the physical size of the pixels on the chip if you the images were taken at other than 1x1 binning. If the images were taken at 2x2 binning, you would enter a value double those shown above and triple the values if shooting at 3x3 binning. Size units Check “microns” if the sizes you entered are in microns. Check “arcsec” if the size is given in arcseconds. This option is offered to accommodate some FITS images that store the pixel size this way. If the pixel size is in arcseconds, then the focal length setting is ignored since the main reason for it is to compute the pixel sizes in arcseconds. Automatic Override of Image Settings The settings for focal length, rows, columns, and pixel sizes allow the program to scale a chart properly when trying to AutoMatch to an image. However, during AutoMatch, Canopus looks at the FITS/SBIG header to see if the necessary keywords are available to provide these settings directly. If the keywords are available and have valid values, the values from the image are used in lieu of the configuration settings. Providing the focal length does not change significantly among profiles, you can create a single profile that works for almost all combinations, e.g., different binnings of the same camera/telescope combination. For this feature to work, the header must have the focal length in millimeters, which is in the SBIG FITS standard adopted by most popular software. This is different from the Canopus configuration setting, which – internally – is stored in inches. When trying an AutoMatch, Canopus (and PhotoRed) first converts its setting to millimeters and then compares that value to the one in the header. If the Canopus and header values differ by more than 30% of the Canopus value, the Canopus value is used. Therefore, it’s important that the focal length setting for a given profile closely matches the focal length of the instrument used to take the images covered by that profile. Header Exposure Time Select the appropriate value to indicate how the exposure time in the image header is related to the true exposure time: Start Mid End The header time is for the beginning of the exposure The header time is for the mid-point of the exposure The header time is for the end of the exposure This setting is used to compute the mid-exposure time, which is the one generally used time for astrometry and photometry record keeping. Prompt for time mode Check this box to be prompted for the time mode (Start/Mid/End) when the program cannot read the image header’s date and/or time. This setting is rarely needed for well-formed SBIG/FITS images. However some programs, e.g., some Cookbook camera control programs, do not have enough information for Canopus to compute mid-exposure and so the program prompts the user each time an image is loaded. Ignore OBJECT KW Check this box to have Canopus ignore the OBJECT keyword in the FITS header when AutoMatching. Canopus attempts to read certain keywords in the FITS/SBIG header to determine where to center the chart for AutoMatching. It gives priority to the OBJECT keyword. If your imaging software assigns a value to the OBJECT keyword that follows the expected conventions but that name is not really appropriate, then the chart will not be 29 centered on the correct position. For example, if you have OBJECT=A1, then Canopus will interpret that to be 1 Ceres and try to draw a chart centered on that asteroid's position for the date and time in the header. By checking this box, you force Canopus to ignore the OBJECT keyword and to rely only on the OBJCTRA/OBJCTDEC, IMAGERA/IMAGEDEC, or WCS-related keywords. See "Reading the FITS/SBIG Header for AutoMatching" on pg. 50 for more information. Ignore FL/Pix Size If the values in the image header for focal length and/or pixel size are in unexpected units or wrong, Canopus may not be able to AutoMatch an image. Check this box to have Canopus ignore the settings in the image header and always use the configuration settings. Miscellaneous – High Precision Check this box to have astrometric position reported to three decimals in RA and two decimals in Declination. Uncheck the box to have values reported with 2 decimals in RA and 1 decimal in Declination. Unless you are using a catalog with high precision positions and your setup provides the necessary level of precision, you should not check this box. Miscellaneous – Min: 1024 x 768 By default, the minimum size of the Canopus form is 800x600. Check this box to make the minimum size 1024x768 pixels. Miscellaneous – Double star precession Check this box to have Canopus precess the RA and Declination for a double star to the epoch of the observation before calculating position angle and distance. It is checked by default and it’s rare that you would have it unchecked. This setting is important to those using the double star measuring and reporting features in Canopus. The catalog values are J2000 but if the observation is made in 2010, the RA and Declination of the star will have changed, especially if the star is near one of the poles. The change in position affects the computation of the position angle and distance of the secondary star in a visual double star. In order to make direct comparisons of observations from different epochs, the RA and Declination must be for the epoch of the observations and not a fixed epoch. Miscellaneous – Image Scaling The default scaling for displaying images can be set to one of two pre-defined options. Both are based on finding the mean pixel value in the image and the standard deviation (1 sigma) of that mean. 30 Normal This sets a +3/–1 sigma range and is good for general viewing. It provides a pleasing look with a reasonably dark sky. Compressed This uses a +0.6/–0.3 sigma range, producing a brighter sky and compressed range. This makes seeing faint objects much easier. While not as pleasing for general viewing, this setting is recommended when doing asteroid astrometry and photometry in order to see if any faint objects are intruding into the innermost measuring aperture. These intruders affect the centroid and photometry data. Miscellaneous – Root Dirs Click this button to display the Root Directories form. The root directories are required to read and write files to the correct location. These values are set during installation and should be changed only if absolutely necessary or you want to have certain files saved to a place other than the default. For each of the entries, you can use the speed button immediately to the right of the entry field to display a directory selection box. To select a directory, its icon must be an open folder. If you click on a directory and the icon stays as a closed folder, double click on the icon so that it becomes an open folder. RootDir This is the directory off which the entire MPO suite tree is built. Do not change this setting unless you move all files associated with the entire MPO suite or the installation program failed to enter the correct value. Changing this setting to match the location of the MPO tree will not guarantee the programs work correctly. The Windows registry includes many entries based on the original install as well. If you want to move the MPO tree, it’s best to make a backup of critical user-files, e.g., “The Might Five” and all exported Canopus sessions files, uninstall the programs, and then reinstall to the new location. Images This is the default directory where MPO Connections images are saved and all MPO programs that work with images look the first time the program is run. After you open an image in one of the programs, the directory is automatically saved and it becomes the default from there on, including from one session to the next. Scripts This is the default directory where MPO Connections scripts are saved. This includes both scripts created in the script editor and scripts saved on the searches page. Scope Pos This is the directory where MPO Connections saves a text file compatible with Technical Innovations HomeDome and ProDome programs. The file contains the current position of the telescope, which when read by the TI programs, allows the dome slit to be properly positioned. All MPO programs use these entries. For example, if you change the settings in Canopus, PhotoRed and MPO Connections use the new values when they are started without you having to change the settings in their configurations. The only settings of general interest in Canopus and PhotoRed are the first two, Root Dir and Images. Miscellaneous – Auto Save Critical User Files If enabled, this feature asks if you want to save the critical user files when the program is closed. The files saved are the “Mighty Five” (see The “Mighty Five on page 10). Enabled Check this box to turn on the Auto Save feature Path Click the browse button to the right of the field to display a directory selection form. Chose a directory where the files will be stored. 31 The path cannot include the root MPO directory. This helps prevent losing these files should the user uninstall the software, not realizing that the files will be deleted as part of the process. Configuration - MPC Page The MPC page sets the default values for a report sent the Minor Planet Center for astrometry. Canopus is ready for when the Minor Planet Center changes to the proposed new astrometry report format. However, do not select this option unless and until the MPC switches to the format. COD This is the 3-digit code assigned by the Minor Planet Center for the location from which the images to be measured were taken. If you do not yet have a code, enter XXX. ID Enter a value from 1 to 9, A-D. This is for observatories that have a single code but might be using different equipment setups, e.g., a 0.5-m f/8.1 Ritchey-Chretien with FLI IMG-1001E in one instance and a 0.25-m f/10 SCT with SBIG ST-9 in another. This allows researchers to determine which setup was used for given data and so give appropriate weighting regarding the quality of the data. BND Select the photometry band in which all magnitudes for the report were made. If no magnitude estimates are included, select “No” from the list. In that case, the BND keyword line is not included in the MPC report header. TYP This keyword is used to indicate which types of objects are included in the MPC reports. The choices are: 32 NEOCP ALL objects are from the NEOCP of the MPC NEO ALL objects are designated NEOs MBA ALL objects are designated non-NEOs UNIDENTIFIED NONE of the objects in the report is identified, i.e., number or name. A user designation is permissible. TNO ALL objects are beyond the Main Belt. This includes TNO, KBO, SDO objects COMET ALL objects are comets. Note that ALL objects in a given report must match the value selected for this field. The MPC requires that there not be a mix of asteroids and comets and, unless UNIDENTIFIED is used, that there not be a mix of the other asteroid types. COM Enter up to 80 characters. This can be a general comment that amplifies or clarifies something about the report. CON1 Enter the complete contact information for the primary observer, including name, address, and e-mail address. The e-mail address must be enclosed by square brackets. Check the MPC web site for proper formatting of this entry. By default, acknowledgments of e-mail reports from the MPC are sent to sending address. See the description for the AC2 entry field below. CON2 Leave this field blank unless there is a need to indicate a secondary contact. If you do include a second contact, be sure to include all information, just as with the primary contact person. OBS Enter the name(s) of the observers. This is usually the person operating the equipment for the images. Note that only initials are used for first and middle names. If more than one name is entered, separate them by commas. MEA Enter the name(s) of those who measured the images. Note that only initials are used for first and middle names. If more than one name is entered, separate them by commas. TEL Enter a brief description of the equipment used to acquire the images. Do not use brand names, e.g., FLI, SBIG, etc. The entry in the screen shot is typical of what one would enter. NET Enter the catalog used to measure the images. Include version and subversion numbers, e.g., GSC 1.1, USNO A2.0. When doing astrometry, it is strongly recommended that you use one and only one catalog for a given set of measurements. ACK Enter a default message that is sent as part of e-mail from the Minor Planet Center when it receives your e-mail. Note that receiving the ACK e-mail indicates only that your e-mail report was received. There is no guarantee that your observations will be immediately processed. AC2 Enter an alternate e-mail address to which MPC acknowledgments are sent. Do not surround the entry with opening and closing brackets as with the entries in CON1 and CON2. If this entry is non-blank, acknowledging e-mails are sent to this address instead of the sending address. TO Enter the address to where e-mail reports should be sent. The default as shown in the screen shot above and when Canopus is first used is the one preferred by the Minor Planet Center. Do not change it unless the MPC changes it or asks you to send e-mail to another address. New MPC Format Check this box to use the proposed new two-line (132-character) reporting format. This includes expanded observatory codes and designations as well as information that helps researchers determine the quality of your data. 33 Do not check this box until and unless the MPC officially adopts the proposed new standard. Canopus is ready to handle that new standard but the MPC will frown upon anyone using it before they are ready. Configuration - Catalogs Page The Catalogs page allows you to set the paths (location) for the files of a given catalog, to set the lower and upper magnitude limits for start to be plotted, and the color of the stars based on the catalog. When doing astrometry, it is strongly recommended by the Minor Planet Center that you use one and only one catalog. For astrometry, the UCAC2 or UCAC3 catalogs are highly preferred since these are of high-precision and included proper motions. The MPOSC3 catalog uses 2MASS positions, which produce excellent results but they do not include proper motions, so their accuracy will diminish over time. General Settings The following applies to all catalogs. Path Enter the path to the MPOSC files. If you installed the catalog, this path should be set to the correct path. You should change it only if you moved the files after installation or copied them directly from the catalog CD to your hard drive. Use the speed button immediately to the right of the entry field to display a directory selection form. Min Enter the minimum (brightest) magnitude of stars from the catalog to be used. The default of –10 assures the brightest stars in the catalog are used. Max Enter the maximum (faintest) magnitude of stars from the catalog to be used. The default of 100 assures the faintest stars in the catalog are used. Color Select one of colors in the drop-down combo box. This color is used to plot the stars from the given catalog. By using different colors, you can quickly determine which stars are from which catalog. 34 Do not select black since the chart background is always that color. Astr. Check the box to have the stars from the catalog used to find an astrometric solution or for setting the magnitude/intensity relationship. If you have the catalog selected but do not check this box, the stars in the catalog are plotted but they are not used for astrometry/photometry but are used for the AutoMatching routine. This helps when you want to use only a high precision catalog for astrometry, e.g., the UCAC2, but there are insufficient stars in the catalog for a given region to get a solid match between a chart and the image. Not included on this page but on the Charting Page are stars from the Position and Proper Motions (PPM) catalog. PPM stars are usually < 6.0m and plotted as bright green. Catalogs MPOSC3 Check this box to use the MPO Star Catalog 3 supplied with the MPO programs. USNO Check this box to use the USNO catalogs. This can be the S or A series, version 1 or 2. The S series is a subset of the A series and has about 55 million solar color stars (approximate color of asteroids). The full A series has more than 550 million stars. If you have the A series, it is recommended that you copy all 10 or 11 CDs (version 1 vs. version 2) to your hard-drive. This saves time both because of faster access to the data and by avoiding CD swapping. UCAC2 Check this box to use the UCAC2 catalog using the CD supplied by the U.S. Naval Observatory. If you use this version, Canopus computes the positions using the proper motions available in the catalog, thus rendering more accurate positions. UCAC3 Check this box to use the UCAC3 catalog using the DVD from the U. S. Naval Observatory that was supplied with the MPO software. This is a double-sided DVD. Most drives will at least be able to read one-side. If you have the disc space, copy all the files from both sides of the DVD to a single directory on a hard drive, e.g., G:\UCAC3. This will make for much faster chart construction and avoid having to flip the DVD to read files that are on “the other side.” APASS Check this box to use the AAVSO APASS catalog. This is included on the MPO DVD. MPO software does not support the native text version of the APASS catalog. The APASS catalog will eventually provide coverage of the entire sky from V ~ 10-17 in the BVg’r’i’ bands. R and Ic magnitudes will be included based on transformation formulae. The precision and internal consistency are hoped to be sufficient to consider any field as having “secondary standards”, which are stars close enough to the standard system to provide “close enough” reductions to the standard systems for most purposes. The APASS catalog will not be completed until sometime in 2012-2013. At this time, it has limited sky coverage. In addition, the photometry has not been fully vetted and refined. Reports on tests using the APASS catalog and are welcomed. 35 Configuration - Charting Page The Charting Page defines some general defaults for charts used for astrometry and photometry. Bin Magnitudes Check this box to have stars plotted by “groups”, e.g., stars of 9th, 10th, and 11th magnitude are plotted with the same size. Uncheck the box to have star sizes plotted as a direct factor of their magnitudes. A slight “bias” is added to stars of 6th magnitude and brighter, which more closely matches what the eye perceives. Fill Stars Check this box to have stars plotted as filled in circles. Uncheck the box to have stars plotted as “open” circles with a single pixel at the center of the circle. The latter setting is preferred since it can show if there is a faint star very near a bright star since the filling in of the bright star does not cover up the faint star. Reverse E/W Check this box to have all charts drawn with West to the left. Uncheck this box to have East to the left of the chart. The AutoMatching feature of Canopus is not able to overcome a case where the image has one horizontal orientation and the chart has the opposition orientation. Use this setting to have the chart approximately match the image. Reverse N/S Check this box to have all charts drawn with South to the top. Uncheck this box to have North to the top of the chart. The AutoMatching feature of Canopus is not able to overcome a case where the image has one vertical orientation and the chart has the opposition orientation. Use this setting to have the chart approximately match the image. Draw Dates Check this box to have the date of the asteroid position plotted just beneath the asteroid position. This option should be off (unchecked) when doing astrometry and photometry but is handy when generating general finder charts covering more than one position. Draw Messier Check this box to plot Messier objects. A caption (label) indicating the name of the object is automatically placed at the upper right of the object. Draw DSO Check this box to plot Deep-sky objects other than those in the Messier catalog. 36 DSO Labels Check this box to have catalog names placed next to DSOs, if plotted. This setting does not affect labeling of Messier objects. LONEOS This group controls the display and use of the LONEOS catalog Plot Stars Check this box to have LONEOS stars plotted. If selected, the stars are red and have a capital ‘L’ next to them unless the star is marked as a Landolt standard. In that case, a capital ‘S’ appears next to the star. Use for Astrometry Check this box to have the stars, if plotted, used to determine the plate constants for astrometry and determine the magnitude/intensity relationship. User Stars This group controls the display and use of the User Stars data. Plot Check this box to plot stars in the User Stars catalog. This catalog can contain entries entered manually or imported from Arne Henden’s many field sequences. If plotted, the stars are read and have a capital ‘U’ next to them. Use for Astrometry Check this box to have the stars, if plotted, used to determine the plate constants for astrometry and determine the magnitude/intensity relationship. Show LONEOS/User Labels Check this box to have the labels associated with the LONEOS and User Stars catalogs displayed. In some cases, given the large number of entries available for a field, you will probably not select this option so that you can see the stars instead of a sea of labels. Rotate °CW Sometimes, using the Reverse E/W and Reverse N/S checkboxes does not bring the chart sufficiently close to the orientation of the image so that AutoMatching can work (or if manually matching, being able to find the pairs of matching stars). In this case, determine a value to rotate the chart a given number of degrees clock-wise so that the orientation of the chart and image are reasonably close. Match Stars This is the maximum number of stars used in the AutoMatch process. The default is a good compromise between assuring that a match is made and speed. The number of iterations goes up dramatically as you increase this number. More iterations take more time. Match Angle This is maximum difference between the derived rotation angle of the chart and the stars in the image. This value is used to restrict solutions to those reasonably close to the orientation of the chart. Max. Scale Diff. Part of an AutoMatch is to scale the chart to that of the image. Sometimes a solution can be found where the scale of the chart is dramatically different from that of the image. In case of a very large field of view, the AutoMatch can appear to “hang” Canopus while it extracts stars for that region. The default of 3.0 says that the chart scale can differ by no more than a factor of 3 from that of the image. Smaller values may prevent a match from being found. Larger values may result in the apparent “hang”. This setting is tied somewhat to the focal length setting in that Canopus generates the initial chart based on that value and the pixel sizes. 37 AM Table Select which table of orbital elements is to be used when doing an AutoMatch. The choices are MPCORB, ASTROB (Lowell), and User. Configuration - Photometry Page The Photometry Page contains a variety of settings related to photometry in Canopus, including default magnitude bands from catalogs and how lightcurve data are plotted. Default Filter Select the photometry band for the catalog magnitudes to be used for plotting charts and setting the M/IR. For unfiltered systems, you would usually select R since most CCD systems come close to the R (or SDSS r’) bands. If you select “C” (clear), V magnitudes are used if available. You must use the same filter in the Comp Star Selector as you set here. See the Users Guide Photometry chapter for tutorials on the Comp Star Selector. Default Dark Enter the full path, including drive, directory, and file name to a default dark frame that is loaded as Canopus starts and then automatically applied to any image that is loaded. Whether or not the dark is used can be overridden from the main menu by checking or not checking Image | Use Dark. Use the speed button to the right of the edit control to locate the desired file and have the full path entered for you. Default Flat Enter the full path, including drive, directory, and file name to a default flat frame that is loaded as Canopus starts and then automatically applied to any image that is loaded. Whether or not the flat is used can be overridden from the main menu by checking or not checking Image | Use Flat. Use the speed button to the right of the edit control to locate the desired file and have the full path entered for you. Photometry Magnitudes The two radio groups in this section determine how magnitudes are computed for lightcurve plotting and analysis. 38 Method Magnitudes used by the Fourier analysis routine can be determined one of four ways: Derived If this method is selected, Canopus computes the target magnitude for each image by Finding the difference between the instrumental magnitudes of the target and each comparison star and then adding the comparison’s catalog magnitude. Finding the mean of the several derived magnitudes for the target magnitude. For this method to work, the catalog magnitudes for the comparisons must be entered in the session data for the active session. The Users Guide shows how to use the Comp Star Selector to enter the catalog magnitudes into the session data when picking comparisons. You can also enter the values manually in the session form if you have accurate values from another source. Instrumental The magnitudes are those determined for each star or the target by taking the total pixel count for the object and applying the eADU setting on the General Page to determine a raw instrumental magnitude. The actual value is based on a formula more complex than a simple log(X) and takes into account how sky background sampling affects the pixel count. It is also normalized to a 1s exposure so that direct comparisons can be made among images with different exposures. Transformed (Deprecated) The target magnitudes are taken directly from the M/IR solution. The comparisons are not used in the calculations at all. Each image should be AutoMatched so that its unique M/IR solution can be used. This method is “deprecated”, meaning that it is still available but should not be used. It is mainly for working with data that was imported from PhotoRed with the presumption that those data were reduced to a standard system to high-precision. When using one of the three methods above, Canopus includes, if appropriate, corrections for changing phase angle and distance from Earth in addition to zero point shifts caused by using different comparison stars in each session. This is explained in more detail in the chapter on the Sessions form later in this Guide. Trans. Absolute (Deprecated) When using this method, no corrections are made for phase angle, distance, or comparison star average offsets. The CompAdjust form is not displayed after finding the period. Also, the Plot Method (see below) is forced to Absolute and cannot be changed. This method is also deprecated and is intended for working with transformed data imported from PhotoRed. Plot Method Lightcurve data can be plotted one of two ways Range The Y-axis values are plus and minus an average magnitude of the data with the average set to 0.0. When the object is brighter than the average, the Y-axis values are negative and towards the top of the plot, in keeping with standard conventions. Absolute In the case of Derived and the two Transformed methods, these will be the catalog-based magnitudes. For “Instrumental” , the Y-axis values are based on the average comparison value adjusted by differential magnitude. Clipping Enter a value from 0.00 to 3.00. This is the number of standard deviations (sigma) above the sky background that a pixel must be before it is included in the calculation of an object’s brightness. 39 When measuring an object, Canopus computes the mean value of the sky background and the standard deviation of that mean. The mean value is subtracted from each pixel within the measuring area for the target (the measuring aperture). The sum of what’s leftover for all the pixels within the apertures is used to compute the instrumental magnitude of the object. The clipping value rejects values that are not at least that many units of the standard deviation above the sky backgrounds (this process is sometimes called k-clipping). For example, if Clipping is set to 0.00, any pixel value that is equal to or greater than the sky background value is counted towards computing the target value. If Clipping is 1.00, then a pixel’s value must be (Background + 1.0 sigma) before it is counted. Setting the value a little above 0.00 can stabilize the derived instrumental magnitudes by filtering out a little noise. Setting the value too high causes stars close to the sky background level to be ignored completely. Even though you can see them, Canopus won’t recognize them if the clipping is set too high. It is recommended that you not go greater than 1.0. If Canopus is ignoring faint stars, lower the value. Plot BMP Size This radio button group controls the size of the 24-bit color Windows BMP or PNG file that is generated whenever you print a lightcurve plot. This does not affect the size of the printed plot or the additional legend bitmap. If you select the Custom button, you should enter the custom values for the bitmap height and width on the Plotting Options tab (see below). This feature is provided to aid those submitting papers in the Minor Planet Bulletin with a large number of plots. For example, if planning to put 8 plots per page in the MPB (with no captions), one would select a size of 1024x675. Some editing will be required with a photo editor, i.e., move the legend to within the main area of the plot and put the name of the asteroid also within the plot area. Miscellaneous Tab The Miscellaneous tab determines how Julian Dates are computed for period analysis, the type of apertures used for photometry, and which files are saved during period analysis. Heliocentric Times Check this box to have Canopus compute the Heliocentric Julian Date for lightcurve analysis. Heliocentric JD is used for variable star work and is defined as the time the light from a star would reach the sun. This eliminates the time difference of up to 16.6 minutes caused by observing the star at one point in the earth’s orbit and then observing the same star six months later when the Earth is 2 AU farther from the star. If the box is not checked, Canopus uses the earth distance in the Sessions form to compute when the light left the asteroid instead of when it reached Earth. This eliminates errors caused by changing distances between the Earth and the asteroid. Also important to understand is that the original date/time in the Canopus data is not altered as a result of these calculations. 40 Both of these methods rely on settings in the Sessions form. The Heliocentric JD correction using the RA/Dec of the object and the light time correction using the Earth distance. The RA/Dec is also used to compute the Air Mass for photometry. The correct RA/Dec values must be set before measuring any images so that the Air Mass values can be correctly computed. Changing the RA/Dec. values after measuring does not re-compute the Air Mass values. If the values are changed, you can use the “Air Mass” button on the Data tab of the Sessions form to re-compute the air mass values. Period in days Check this box to have the period reported in days instead of hours, the standard for variable star work. If not checked, periods are in hours, the standard for asteroid lightcurve work. Show M/IR Form Check this box to display the photometry residuals form and have the program switch to the Reductions page after you AutoMeasure an image. If the box is not checked, the residuals form is not displayed and the program does not switch pages. Turning off the residuals form saves some time if doing AutoMeasure on other targets, e.g., double stars. Saturation This is the value, in analog-digital units (ADU) where Canopus should presume a pixel is either saturated or reach the non-linear response of the camera. For 16-bit camera, the maximum possible value is 65535. However many cameras, especially those with anti-blooming gates or when worked at 2x2 or higher binning go non-linear long before reaching the maximum ADU value. If working with 32- or 64-bit images, the saturation value is so high that it’s highly unlikely that saturation will ever be reached. If working with such images, check the “Ignore Saturation” box. This setting is very important in that it affects all astrometry and photometry measurements. If any pixel in a star reaches the saturation point, that star is ignored for astrometry and will yield bad results in photometry. Ignore Saturation Check this box to have Canopus ignore the saturation setting and to include stars that have reach saturation in astrometry or photometry. Checking this box is not recommended since using saturated or non-linear pixels generates bad results. Max MIR s.d. This is actually the maximum error between the MIR derived magnitude for a star and its catalog value when Canopus initially computes the MIR. Initially up to 75 stars are in the solution. Canopus then goes through and removes stars that have errors at or above this level. This helps eliminate stars with bad catalog magnitudes or that had non-linear pixels below the saturation limit. To see the effect of this value, set it to 0.1 or 0.2 mag and AutoMatch an image. Look at the MIR solution in the Photometry toolbar. Then set this value to 0.05 and AutoMatch the same image. Compare the MIR offset and, more important, SD (standard deviation). If you can get the SD value to < 0.03 mag with at least 20 stars, then you have a fairly reliable MIR solution. That is a rule of thumb, not an absolute rule. Min SNR This is the minimum SNR for the target or comparison star must have before it will be accepted when measuring images with the Lightcurve Wizard and Image List. The default is 10, which is approximately 0.1 mag precision. On occasion, you may need to measure images where the SNR for the target is less than the default. In this case, you can set the minimum acceptable SNR for photometry to a value as low as 1 (approximately 1 magnitude precision). It is strongly recommended that you do not use an SNR < 10 except in very rare circumstances. The precision of the measurements will be very low. In addition, trying to measure very faint objects may just result in data with so much scatter (noise) that it is off little or no use. This feature was added for those cases where an object was above the limit for most images but dropped below the default for a small subset of images, e.g., a near-Earth asteroid that is tumbling and has unexpected and severe magnitude drops. 41 Save Options Tab AutoSave raw data Check this box to have the calculated data used for lightcurve analysis written to a text file each time you do a period search. The files are saved to the \MPO\CANOPUS directory and use the name in the Object field of the Sessions form. See “Viewing the Raw Data” on page 153. If you check the AutoSave raw data box, you must select at least one of the following: Con. No No Condensed data file. This is mutually exclusive with the other two Condensed options, i.e., you can select only one of them. Con LTC Condensed data file with JD corrected for light-time or to Heliocentric JD. Other than the header, the only data written are the JD, magnitude, error, and session number. This is mutually exclusive with the other two Condensed options, i.e., you can select only one of them. Con NLTC Condensed data file with raw JD values, i.e., not corrected for light-time or to Heliocentric JD. Other than the header, the only data written are the JD, magnitude, error, and session number. This is mutually exclusive with the other two Condensed options, i.e., you can select only one of them. Full Text Saves all possible data, including values for each comparison star. This can be used in addition to any other option. BMaker Saves only the phase and flux value. This file is compatible for import into Binary Maker 2 and 3. Note that BM 2 allows only 215 data points. If there are more values than this in the file, you need to remove points at random such that you maintain evenly spaced data over the entire cycle of the curve. This can be used in addition to any other option. Phased Saves the same data as BMaker plus the differential magnitude. This can be used in addition to any other option. Plot Data This contains the X/Y values that appear in the lightcurve plot when searching for a period. If using the “Raw” option, the X-values are Julian Dates. If plotting “phased data” (the data folded to a specific period), the X-values are the phase. Plotting Options Tab Plot with dots only Check this box to have all data points plotted as black, filled-in circles. If using data from more than one session, Canopus automatically uses a different plot symbol and color for the data in each session. This makes it easier to get the zero points for the data lined up. However, sometimes it is better to have all data points plotted as a small filled-in circle, e.g., some publications prefer this format. 42 Monochrome Plot Check this box to have the plot use the standard symbols but make them all black. This can used for submitting plots to publications that require monochrome plots. With Canopus, there are 7 possible symbols and 7 possible colors when not using this option, which makes for a set of 49 combinations. Using this option reduces the number of combinations to 7. The symbol and color assignment are made based on the remainder of the session number divided by 49. Should the remainder be the same for two or more sessions, those sessions will be plotted with the same symbol. If you use this option, with all symbols being black, then it will make it more difficult to distinguish which data points correspond to a given session. Center on mean mag Check this box to have differential magnitudes split evenly above and below 0, with the zero point being the average magnitude of the target data being analyzed. This setting applies only when the plot method is “Range.” Extrema at 0% Check this box to have a maximum or minimum forced to be a 0% phase when plotting lightcurve data by phase. If this box is checked, the Min and Max checkboxes underneath are enabled. Max Check this box to have a maximum plotted at 0% phase. If there is more than one maximum and the maxima are unequal, the brighter maximum is used. This setting is often used for asteroids and long period variable stars. Min Check this box to have a minimum plotted at 0% phase. If there is more than one minimum and the minima are unequal, the faintest minimum is used. This setting is often used for eclipsing binary stars. Show Header/Footer Check this box to have the title and period information displayed as the header and footer of the plot. If not checked, these are hidden. The latter option might be used when generating plots for publication. Show Normalized Plot Check this box to display a plot of normalized data for Binary Maker. You must check "AutoSave Raw data" and "B. Maker" before you can set this option. A plot is not displayed if all three options are not set. MPB Phased Plots Check this box to generate phased plots that follow the convention in the Minor Planet Bulletin where the horizontal axis covers about 110% of the period, i.e., -5% to 105%. All plots submitted to the MPB should use this option. Uncheck the box to generate a plot that covers between 1.00 and 2.00 cycles. In this case the plot starts at 0% and goes to the maximum set with the “Plot cycles” field. Plot Cycles Enter a value from 1.00 to 2.00 or use the spinner control to the right of the field to set the value. The value determines how many cycles of the period are covered in a phased plot. The entry field and spinner control are enabled only if the “MPB Phased Plots” box is not checked. Plot Width/Height Enter the width and height, in pixels, when using the “Custom” option for the plot bitmap size. This feature is provided to aid those submitting papers in the Minor Planet Bulletin (or other publication) with a large number of plots. For example, if planning to put 8 plots per page in the MPB (with no captions), enter 1024 and 675 for the width and height, respectively. Some editing will be required with a photo editor, i.e., move the legend to within the main area of the plot and put the name of the asteroid also within the plot area. The sizes just suggested should result in final plots are about 1024x550 pixels, which just fits eight plots per page with no captions. 43 44 Generating Quick Charts Canopus includes a basic chart generator beyond that used to produce the measuring charts for astrometry and photometry but with less flexibility than in the Charts Generator of the MPO Asteroid Viewing Guide. You can generate a chart for locating reference stars from the LONEOS catalog for photometry or to make a chart of the field of the asteroid or variable star being worked to get information on stars in the field. This is useful for finding suitable comparisons for differential photometry. Charts are forced to 2000 pixels on a side, providing a chart of about 6.67 inches when printed at 300 dpi. If your printer has a different resolution, Canopus automatically scales the chart so that it remains 6.67 inches Charts can be 1°, 2°, or 5° per side. Generating a Quick Chart To generate a quick chart, switch to the Charts Page (<Ctrl+5> or use the spend button on the main toolbar. You can select Pages | Charts from the main menu. This chart shows two positions for 1 Ceres in 2009. The red box is a field of view (FOV) of 20 arcminutes per side. The Chart button is disabled until you select the elements for a given object or click the “Position” radio button. If you selected the Position panel and then select the Elements panel, the Chart button is again disabled until you select an object from the specified table. General Information The look and detail of the charts is determined by settings on the Configuration form’s Catalogs and Charts page, where you set which catalogs are to be used to generate charts and exactly what is plotted and how. See the sections on the Configuration | Catalogs and Configuration | Charting pages. Generating a Chart by Orbital Elements Use this method to generate a chart based on orbital elements from the MPC, Lowell, or User tables. 1. Click the “Elements” radio button at the lower part of the form. 2. Select the table in the drop down list from which the elements are to be taken, i.e., MPC, Lowell, or User. 45 3. Click the speed button next to the drop down list to display the objects in the selected table and select the desired asteroid - see Asteroid Selection Form. 4. Set the Universal Date and Time for the first position of the object. 5. Enter the number of positions to chart in the “Pos.” field. 6. Enter the interval in days (or hours) between each position. 7. Check the Days box if the interval is in days. If the interval is in hours, uncheck the box. 8. If generating positions that cover more than 24 hours, you should use an interval expressed in days, even if the interval is not an whole number of days. 9. Check the Flip E/W and Flip N/S boxes as needed. The normal orientation (neither box checked) is to have North at top and East to the left. 10. Select the chart scale (1°, 2°, or 5°). 11. Click the Chart button to generate the chart. Generating a Chart by Position Use this method to generate a chart centered on a given position. 46 1. Click the "Position radio button near the center of the lower part of the form. The Positions panel turns silver while the Elements panel turns dark gray. 2. Enter the Right Ascension in the HH:MM:SS format. Use leading zeros as necessary, e.g., 02:45:06 3. Enter the Declination in the ±DD:MM:SS format. Use leading zeros as necessary. You must also enter the + or – symbol in the first character position, e.g., +41:04:10. 4. Check the Flip E/W and/or Flip N/S boxes as needed. The normal orientation (neither box is checked) has North at top and East to the left. 5. Select the chart scale (1°, 2°, or 5°). 6. Click the Chart button to generate the chart. Blinking Images Canopus allows you to blink two or more images, i.e., to display alternating overlapped images. After the images are aligned, the stars will not move but any moving object will jump back and forth. This is the electronic version of the blink comparator that Clyde Tombaugh used to discover Pluto. If you need to scale the images to make faint objects more apparent, open one of the images and use the image scaler to change the appearance of the image. Then select Image | Sticky Scaling on the main menu. Every image that you open from there on will use the scaling settings. If the images raw scaling changes significantly such that a constant scaling factor won’t work, you can scale each image as you open it, but do not select the Sticky Scaling menu item. The Moving Object Search feature of Canopus can help you find objects if you have a large number of images to review. The Blinker Page can be reached three ways. 1. Click the speed button on the main toolbar. 2. Select Pages | Blinker from the main menu. 3. Press Ctrl+2 from the keyboard. At the top of the Blinker page are four buttons. Open Click to display a file open form. Select one or more images to be blinked. The images are blinked in the order they are opened so you should open the images in increasing time order. If you open more than image at a time, Canopus sorts the files by name. Therefore, it helps to have a numbering scheme built into the file names to indicate the order the images were taken. MPO Connections automatically provides this feature. Start After all the images to be blinked have been opened and the common star selected on each (see the next section on using the Blinker form), click this button to start blinking. A special form is displayed with a Zoom window. The original images are minimized so that you can re-measure the common star or view image information without having to use the Open button again. Invert Speed Button Click this button to invert all open images being used for blinking. This causes dark pixels to be light and light pixels to be dark. You can toggle the images between positive and negative state by clicking the button more than once. The button is enabled only when the blinker is paused and so the image in the blinker form is not immediately affected. When the blinker is started, the image in the blinker form displays the images in their new state. Clear Close the blinker form and the original images. See the tutorial in the Users Guide “Core Operations” chapter on using the Blinker. 47 48 Astrometry Overview The purpose of the astrometry routines in Canopus is to measure the accurate position of an asteroid or other target so that you can report the information to the Minor Planet Center or other organization. It usually takes only a few seconds to perform all the essentials of astrometry, from opening the image to generating an MPC report. As the expression says, “The devil is in the details”. You should be familiar with the details so that you can produce the highest quality data possible. The general outline for astrometry follows. Links to those “devilish details” are given as needed. 1. Make sure you have the correct configuration settings for the image(s) you're going to measure. Canopus attempts to use the necessary values in the FITS/SBIG headers and fall back to the configuration settings if the values are missing or disagree too much with the configuration settings. See “Automatic Override of Image Settings” on page 29. 2. Open an image to be measured by using Image | Open from the main menu. 3. Set the measuring apertures. 4. Select Image | AutoMatch/measure from the main menu. See “What is Chart Matching?” on pg. 50 for more information. If necessary, e.g., Canopus cannot interpret the image header correctly to determine which object is being measured, generate a chart manually and match it to the image. 5. After a match and if the configuration settings allow, the Photometry Residuals form appears. You can adjust the Magnitude/Intensity Relationship at this time, if needed. If not, or you are using only instrumental magnitudes for analysis, then close the form. 6. After a match, Canopus automatically switches to the Astrometry Reductions Page. If necessary, change which stars are used in the solution (see “Astrometry - Changing the Astrometry Solution” on pg. 61). 7. Once you're satisfied with the results, save the data. If you have more images to measure, repeat the above steps as needed. 8. The final step is to generate an MPC report. This generates a text file that you would attach to an e-mail to the Minor Planet Center. Users Guide Tutorials The “Core Operations” and “Astrometry” chapters in the Users Guide cover measuring positions with Canopus. They also include some important basic background. The following sections will cover only additional details not covered in the Users Guide. Astrometry/Photometry Measuring Apertures The measuring apertures are seen whenever you click on an image. They can be three squares or circles (or rectangles/ellipses). The data completely within the inner aperture are the “target data.” The area completely within the “sky annulus”, i.e., the defined by the outermost and next inner circle in the image above, contains the “sky data.” The middle region is the “dead zone.” This is used to keep pixels from being used for both the target and sky data. It also helps avoid using pixels from stars adjacent to the target. The sky background is computed by an iterative process involving the median and standard deviation values along with “k-clipping”. The derived value is subtracted from the value for each pixel in the target area. The resulting target values are then used to compute the centroid position, signal-to-noise ratio (SNR), instrumental magnitude, and Full-Width Half-Maximum (FWHM) value for the star. 49 Canopus has been well tested using both rectangular and circular measuring areas. Tests on standard fields that produced 0.01m and better photometry after finding the transforms and nightly zero points and thousands of astrometric observations accepted by the Minor Planet Center fully validate the methods of the Canopus system. Just as important, the sky background routine has been tested for constancy when including or excluding any number of field stars – including a those much brighter than the target. The instrumental magnitudes of the target with various sky annulus settings usually showed a standard deviation of ~ 0.01 mag, indicating that the sky background routine is very stable, which implies a similar stability in the magnitudes for the target as well. This becomes important when measuring in crowded fields where, despite some conventional thinking, it’s better to use a larger sky annulus than smaller one so that the number of empty sky pixels dominate over those from field stars. What is Chart Matching? Matching (or aligning) the chart means adjusting the initial chart so that for any star on the chart and its counterpart on the image, the X/Y distance and angle from chart center is the same as the X/Y distance and angle from image center. In mathematical terms, assuming the center of the image and matched chart to be the original of a polar coordinate system, a given object that is on both will have the same polar coordinates. This is done in Canopus by using a two-star alignment method. Two stars in the image are selected that have counterparts in the initial chart. The stars should not be too close together in order to allow the best possible scaling. Also, a line joining the two stars should not be vertical or horizontal, i.e., not parallel to either the X or Y axis, otherwise it's difficult to determine image rotation accurately. Once the chart is matched, Canopus can then match any star in the chart to a counterpart on the image or vice versa, unless – of course – there is no counterpart. This can occur for any number of reasons, e.g., the chart catalog being incomplete to the limiting magnitude of the image or the star is a nova or asteroid. By default, Canopus assumes that the image has north at the top and east to the left and that the north-south line is vertical, or nearly so. If this is not the case, e.g., the images are rotated 180° such that south is at the top and west is to the left, use the Configuration settings so that the initial chart matches the image as closely as possible. Also important is that you have the focal length of the system set as closely as possible, i.e., within 30%. If you don’t have the right Configuration settings, the AutoMatching feature may not work reliably, if at all. Generating a Chart for Astrometry In most circumstances, you’ll use the AutoMatching feature of Canopus to generate the chart for astrometry and photometry. However, you can generate a chart “manually”. This is required when Canopus cannot determine the object from the SBIG or FITS header (or if the image is BMP or JPEG format). Canopus can still perform the AutoMatching if you want, it’s just asking for help in a given circumstance. 50 The Chart Generator Form The Chart Generator form is used to generate a chart based on asteroid location or specific RA/Dec. Chart based on Use the drop down list to pick the table from which the orbital elements are to be taken or to generate the chart centered on a fixed position. Number Enter the number of the asteroid, which must be in the range of 1 to the highest numbered asteroid in the database. This control is disabled if Position is selected in the “Chart based on” list. To search for an asteroid by name or number, click the speed button next to this field. This displays the asteroid search form. Select the desired asteroid and click OK the search from. RA Enter the Right Ascension of chart center when "Chart based on" is set to "Position". The format is HH:MM:SS. Use leading zeros if necessary. For example: 02:45:33 Dec Enter the Declination of chart center when "Chart based on" is set to "Position." The format is ±DD:MM:SS. You must enter the + or – and use leading zeros if necessary. For example: +02:45:10 or –23:02:00. Date Enter the date based on Universal Time. The format follows your Windows Regional Settings, with the exception that you must enter all four digits for the year. Use the date corresponding to the Universal Time of the mid-point of the exposure. If generating a position by asteroid, the date must be in the range of 1950 January 1 to 2050 December 31 since this is the range of the pre-computed planetary positions. To generate a chart outside this range, find the asteroid's J2000 position using another program and generate the position based on that position. U.T. Enter the time in HH:MM:SS format using a 24-hour clock and use leading zeros if necessary. For example: 1:14:15 pm = 13:14:15. Use the Universal Time of the mid-point of the photo. The Date and time are entered automatically if Canopus can retrieve them from the FITS/SBIG header. The values are for mid-exposure as based on the data in the header and the configuration settings regarding header time in relation to start/middle/end of exposure. Canopus must also be able to read the exposure time from the header in order to compute mid-exposure. 51 Reading the FITS/SBIG Header for AutoMatching When AutoMatching, Canopus tries to generate the chart automatically by looking the FITS/SBIG header for certain values so that it can determine the RA/Dec of the chart center to be built. It does this by trying to interpret the OBJECT and OBJCTRA/OBJCTDEC keywords. If possible, your imaging software should try to use the conventions outlined below to help assure that AutoMatching works. The OBJECT Keyword Canopus attempts to interpret the OBJECT field in the following ways. Example: A1417 If the value starts with ‘A’ and is followed by a number, the ‘A’ is removed and Canopus attempts to convert the rest of the value to a number. If that succeeds, the assumption is that the object is a numbered asteroid and chart center is based on the computed position using the date and time in the FITS header, adjusted as necessary by the configuration settings to Universal Date/Time. If the conversion to a number does not succeed but the OBJCTRA/DEC keywords have valid entries, then Canopus uses those fields to center the chart. Example: 1417 If the first and second characters are a number and there is no space in the value, then Canopus attempts to convert the value to a number. It then proceeds as outlined in Example 1. Example: 1999 CZ1 If the first and second characters are numbers and there is a space in the value, the assumption is that the value is an unpacked MPC designation. Canopus converts the value to the packed form and then back to unpacked. If the original value and the returned unpacked string are the same, then Canopus tries to find the asteroid in the MPC database and, if found, proceeds as in the case of a numbered asteroid. If the packed-to-unpacked test fails or the asteroid is not in the MPC database but the OBJCTRA/DEC fields have valid values, the chart is centered on the position in those fields. Example: Ceres Canopus attempts to do a name lookup in the MPC data. If found, then Canopus proceeds as in the case of a numbered asteroid. If not found, but there are valid entries for the OBJCTRA/DEC keywords, the chart is centered on the position indicated in those fields. Connections can be set to use one of the conventions above when adding the OBJECT keyword to a FITS image by defining the base name for the images. Thus, Canopus can automatically determine which asteroid you were working, numbered or unnumbered, and generate the chart based on the asteroid’s position at the time that the image was taken. When using the AutoMeasure feature of Canopus, where it matches a chart to the image, having the OBJECT keyword set properly allows Canopus to measure the position of the asteroid automatically. If the chart is based on position only, no such attempt is made. The OBJCTRA/OBJCTDEC and IMAGERA/IMAGEDEC Fields If the OBJECT field does not contain a valid entry as defined above, then Canopus uses the settings in these two fields. If connected to a telescope, Connections sets these fields for you. Whenever you take an image with MPO Connections with the telescope connected, the RA and Declination reported by the scope are recorded into the FITS header under these two keywords. This is particularly important if you are working a target other than an asteroid since, most likely, the OBJECT field will not be interpreted as an asteroid. 52 If there is no telescope linked, you can still have Connections insert the position into the FITS header by using the “RA/DEC from GoTo” checkbox in the Configuration settings. This means that the RA and Declination are taken from the two “GoTo” fields normally used to slew the scope to a given position. Naturally, you need to be sure these two fields are set correctly before taking each image. Valid Formats for OBJCTRA and OBJCTDEC The entries for these two fields in the FITS header must be in the following format so that Canopus can convert them correctly (and so that the entries match the NOFS FITS standard). OBJCTRA OBJCTDEC HHxMM[xSS[.ss]] ±DDxMM[xSS[.ss]] Where ‘x’ represents either a space or colon ( : ) and the entries within the square brackets are optional. Use leading zeros to fill a field completely. For example, ‘03’ and not ‘ 3’. For declination, you must enter the sign ( + or – ) as appropriate, i.e., the sign symbol is not optional. If the OBJCTRA/OBJCTDEC keywords are not present but IMAGERA/IMAGEDEC are, then Canopus will try to read the values in those two keywords and generate a chart based on the corresponding position. The formatting requirements for the values are the same as for OBJCTRA/OBJCTDEC. If all else Fails If for some reason your image(s) don’t have entries that can be properly interpreted by Canopus, you can use the Image Header Editor in Canopus to enter values into the appropriate fields. The editor allows you to change keywords for one image at a time or a number of images in the same folder in one pass. See page 211 for information about the Editor Manual Astrometry The manual method of astrometry in Canopus serves as the foundation for the automatic method. If using the AutoMeasure method, every step in the manual method is still performed. If you understand the manual method, then you know how Canopus works behind the scenes and so, if you have trouble, you have a better idea of how and where things might be going wrong. Basic Steps in Manual Astrometry Manually measuring an image requires several basic steps. Instead of covering them here, refer to the tutorials in the “Astrometry” section of the Users Guide, found in the \MPO\DOCS directory. The Photometry Residuals Form The screen shot above shows the initial M/IR solution after an AutoMatching. If a star is used in the solution, the cells in its row are white. If the star is not used in the solution, the cells in its row are silver. 53 U If this box is checked, the star is used in the M/IR solution. To change the status of the star, click on the box so that it reverses from check to unchecked or vice versa. Each time you change a star’s status, Canopus re-computes the M/IR solution and the values in the Res column change, as does the background color of the row for the star. Name/Area and GSC/# These fields identify the star. The number in the far left column corresponds to the number seen on the chart for the star. RA/Dec These fields display the catalog position for the given star. X/Y These fields display the measured centroid position of the star Mag This is the catalog magnitude taken from the catalog. Note that the column with the star numbers, just to the left, has a color background. If the cell is red, the Red magnitude of the star is being reported. If the cell is blue, the Blue magnitude of the star is being reported. If green, then the V magnitude is being reported. Astrometry - Changing the M/IR Solution Why do you need to worry about setting the M/IR if all you’re doing is astrometry? The main reason is to be able to report a reasonable estimate of the magnitude of an unidentified or new target, e.g., a new asteroid or supernova. If the initial M/IR solution is significantly off, then the estimated magnitudes will be significantly off, especially those at the bright and faint end of the solution. As noted before, the M/IR derived magnitudes in Canopus are based on catalog values that may have considerable systematic errors, which is not consistent across the catalog. Errors in the M/IR solution can also be the result of a bad mismatch between your system and the color band chosen. The good news for those wanting to do higher accuracy photometry is that Canopus can use the 2MASS conversion in the MPOSC3 to achieve 0.05-0.10 absolute accuracy in most cases and 0.01-0.02 mag internal consistency, all of which makes matching night-to-night sessions easier. For even greater accuracy, the Canopus data can be imported into PhotoRed where instrumental magnitudes are converted to standard magnitudes using transforms that define your system in relation to the standard system. The “Max MIR s.d.” setting on the Configuration | Photometry page affects the initial M/IR solution. See that section for additional information. Changing the Solution Set If you change the setting in the U column in the Photometry Residuals Form for a given star, Canopus re-computes the M/IR and residuals for the stars still being used. The new M/IR solution is displayed in the photometry status bar towards the upper right of the main Canopus form. Canopus attempts to find a solution with the most number of stars where all stars have a maximum error of about 0.05m (default; the “Max MIR s.d.” value sets the limit). Check the solution to see that at least some stars at the faintest end are included. Do the same for stars at the brightest end, with one caveat: don’t include stars that are over-exposed. They are most likely saturated. In a perfect world, you're looking for a solution that has as low of standard deviation (SD) as possible. However, there is a minimum limit of ten stars for the solution, so excluding “bad” stars can go only so far. 54 AutoMeasure (AutoMatching) AutoMatching and measuring an image is much easier than manually matching an image. See the “Astrometry” chapter of the Users Guide for tutorials on AutoMatching. Astrometry Reductions Page The Reductions Page can be displayed automatically after Canopus matches a chart to the image if the “Show M/IR form” box is checked in the configuration or manually shown by going to that page with the Pages menu or pressing Ctrl+3. The Reductions page is divided into several sections. Before describing those, you should understand how Canopus arrives at the initial astrometric solution. Auto Reference Star Removal If you do an AutoMeasure, Canopus automatically reviews the residuals for the reference stars and removes those stars with excessive residuals. Unlike a common approach where any star in the initial solution with an error > 0.40 arcseconds is rejected out of hand, which could remove stars unnecessarily, Canopus finds the single “worst offender”, removes it from the solution, and re-computes the residuals for the remaining stars. It repeats this process until all stars have a maximum residual of < 0.40 arcseconds in both RA and Declination or until there are only ten stars in the solution. Even with these somewhat tighter standards, it’s very common when using the full MPOSC3 catalog to have at least 50 stars in the solution set (assuming there are at least that many stars in the image!). In the example above, Canopus immediately removed 5 stars. You’ll get slightly better results in many cases when using the UCAC 2/3 catalogs, with the standard deviations of the solution being smaller. This is mostly due to those catalogs included proper motion information that Canopus uses to generate positions for astrometry. The Initial Solution In addition to the reference star catalog positions and X/Y coordinates on the image, several pieces of data must be available to Canopus to complete the reduction calculations. In many cases, they are automatically entered, being taken from the image header (if using a FITS or SBIG image) and the center of the chart that was generated to measure positions. Usually, most of the following steps have already been taken. Save for step 1, you do not need to repeat them – including calculating the residuals and position of the target. However, it is a good idea to always confirm that these steps have been taken, either manually or automatically. 1. Enter the object’s name on the Object Information area on the page. 55 2. Enter the date of the mid-point of the photo. Remember to enter all four digits of the year and the format is yyyymmdd. 3. Enter the Universal Time of the mid-point of the photo in hh:mm:ss 24-hour format. 4. Enter the approximate RA of the center of the photo in hh:mm:ss format. 5. Enter the approximate Declination of the center of the photo in ±DD:mm:ss format. 6. Make sure the correction number is in the Asteroid # field (if this is a known target) and click the Recompute button. If the target is not in any of the catalogs, enter 0 for the number and make sure the other fields mentioned above are correct. Color Coding To make reductions go faster, the RA and Dec residual columns in the Data Table are color-coded. This indicates the level of residuals in the RA and Dec. If the standard deviations are sufficiently low and there are no stars with excessive residuals then your work is done except to save the data. Reductions Page - Astrometry Data Table The table displays the following information about each star selected by the manual or automatic methods. Star Count The upper leftmost cell shows the number of stars being used in the solution, i.e., those with the "U" box checked. Zone This is the star's number within the catalog section. For MPOSC3 stars, this is the MPO3 identifier and first part of the RA. For stars from the GSC catalog, this is the zone number. If using the UCAC catalogs, the entry is always 2(or 3)UCAC. # The number of the star within the catalog section. For MPOSC3, it is the declination part of the identifier. U(se) Check this box to use the star in the astrometric solution. Uncheck it to remove the star from the solution. Whenever the state of the box is reversed, e.g., from checked to unchecked, Canopus automatically re-computes the astrometric solution. RA/Dec These fields display the catalog Right Ascension and Declination of the star. Mag This field displays the catalog magnitude of the star, not the derived magnitude from the M/IR. Which color band is represented depends on the Configuration settings (Photometry Page) and the magnitudes available in the catalog. For example, if from the Tycho 2 catalog, V magnitude is always used. If from the USNO catalog, the “V” magni- 56 tude is used (this is computed on-the-fly and is only roughly approximate). If the LONEOS catalog, then the Configuration setting dictates which magnitude (BVRI) is used. X/Y These are the X and Y values for the measured centroid of the star. RA/DCRes These indicate the “backfit” of the catalog vs. derived position. Once Canopus derives an astrometric solution for the image, it uses the measured X/Y centroid values to compute the RA and Declination of the star. These computed values are subtracted from the catalog value to yield the error for each star’s position. Canopus computes the standard deviation of these errors and reports the results in the Object Information section of this form. The standard deviation values provide a quantitative assessment of the astrometric solution and the estimated error of the derived position for the target. The RA residuals are in arcseconds, i.e., DeltaRA * 15 * cos(Dec). The color and values in these two fields of the table give a quick indication of the quality of the backfit for a given star or if the star is or is not used in the astrometric solution. Reductions Page - Object Information This section provides information about the target, if any. Name Name of the target, enter up to 20 characters. If Canopus was able to determine from the image header which object was in the image, this field is usually entered automatically. If entering the designation of an asteroid, do not use the MPC packed designation, e.g., use 1999 CZ1, not J99C01Z. X/Y These fields show the measured centroid of the target. Mag This indicates the magnitude of the object as determined from the Magnitude/Intensity Relationship (M/IR). If using the MPOSC3 or UCAC2/3 catalogs with 2MASS magnitudes available and if the standard deviation of the M/IR is reasonable (e.g., < 0.05 mag), then this is a reasonable estimate of the object’s magnitude. The magnitude is in the band selected by the “Default Filter” setting on Configuration | Photometry page. SNR This gives the measured signal-to-noise ratio for the object. This can be converted to an approximate error in magnitudes by 1.0857 / SNR. MPC Name This is the name used in the e-mail report for the Minor Planet Center. When you generate a chart for astrometry, Canopus works out what this field should be and automatically enters it for you. If the asteroid is numbered, you'll see the number with as many leading zeros as required to make a string five characters long, e.g., '01424' (seven characters if the revised MPC format is used). If the asteroid is unnumbered, you'll 57 see the packed designation, as in the screen shot above. You should always double-check this field to be sure that it is correct. If it isn't and you send in a report, you'll receive a note back from the Minor Planet Center about a bad identification. Right Ascension and Declination All fields are read-only Measured The measured J2000.0 RA of the object S.D. This is the standard deviation for the measured RA or Declination based on the errors of backfitting the astrometric solution to the catalog positions of the reference stars. The RA is in arcseconds, i.e., RA * 15 * cos(Declination). Calc This is the calculated J2000 position of the asteroid. M-C The measured minus calculated value in RA and Declination. Both values are in arcseconds. Reductions Page - Observation Codes / Processing Use the drop down box to select the appropriate choice for these three items. Note1 If appropriate, select one of the MPC codes to be included in the given observation. The codes indicate such things as poor solution, target merged with star, etc. Note2 Select the method of measurement. The default is CCD. Mag. Code If appropriate, select the magnitude band for the reported magnitude. The default is “X”, which means to exclude the derived magnitude in the report. Change this value if you want to include the computed magnitude in a report the Minor Planet Center. If you chose to report a magnitude, select the band set by “Default Filter” on the Configuration | Photometry page. If you’re not sure, don’t report the magnitude or at least make it clear how the value was determined. 58 Reductions Page - Fixed Data The fixed data section displays information about the image. Date/UT These are the Universal Date and Universal Time of mid-exposure. Canopus attempts to read the image header for the recorded date and time as well as exposure duration. If these are available, then the configuration settings for UTOffset are used to compute the UT Date/Time of mid-exposure. If Canopus cannot read the header information, it prompts you each time an image is loaded for the UT Date/Time of mid-exposure. See “Configuration - General Page” on page 27. RA/Dec These are the RA and Declination of the center of the image. Initially, Canopus tries to read the OBJCTRA and OBJCTDEC fields from a FITS header (or IMAGERA/IMAGEDEC) and places those values in these fields. If they are not available, the computed position of the asteroid – if computed – is used to fill these fields. Once the chart has been matched to the image, Canopus changes these fields to reflect the computed center of the image based on the astrometric solution. Focal Len This field displays the computed focal length of the system used to take the image based on the astrometric solution. Calculations Section The calculations section is used to re-compute the astrometric and Measured minus Calculated values. This can be necessary if the initial chart was generated by position or Canopus could not properly determine for which asteroid to compute a position. Asteroid # Enter the number of the asteroid for which a position is to be generated. If you don’t know the number in the catalog, click the speed button to the right of the field. This displays the Asteroid Search form. Recompute Click this button to recomputed the astrometric and residuals using the set of elements for the asteroid indicated by the Asteroid # field. 59 Reductions Page - File Operation Save Click this button to save the astrometric data for the given observation. All astrometric files are forced to have the extension AST. Load Click this button to load a previously saved astrometric solution. After doing so, double check the number in the Calculations section as well as the Name and MPC Name fields in the Object Information section. When working with unnumbered asteroids and you’ve updated the asteroid database since the observation data was saved, the number of the asteroid may have changed (or the asteroid has become officially numbered). If this is the case, correct the number in the Calculations section and recompute the solution. If satisfied with the results, save the observation. Print Click this button to send the details of the astrometric solution to a printer or to a text file, as selected by the radio group below the button. When you click this button, the Select AST Files form appears. Select one or more files for which you want to print the data. When printing or sending the data from an astrometry file, the output now includes the plate constants for the given measurements. For example: Reduction Constants: Zeta1: -0.0000117965 Eta1: +0.0000001727 Zeta2: -0.0000001730 Eta2: -0.0000117991 Zeta3: +0.0034524788 Eta3: +0.0026405209 To get position from constants: Zeta = (Zeta1 * X) + (Zeta2 * Y) + Zeta3 + (X / FL) Eta = (Eta1 * X) + (Eta2 * Y) + Eta3 + (Y / FL) RATemp DCTemp = cos(DCCenter) - Eta * sin(DCCenter) = SQRT(SQR(Zeta) + SQR(RATemp)) RA = RACenter + ArcTan(Zeta / RATemp) DEC = ArcTan((sin(DCCenter) + Eta * cos(DCCenter)) / DCTemp) 60 Where X/Y FL RACenter DCCenter Sqrt Sqr ArcTan X/Y coordinates of the object on the image Focal Length in microns, i.e., FL (inches) * 25400 Estimated center of image, Right Ascension (degrees) Estimated center of image, Declination (degrees) Square Root function Square function Inverse Tangent and must be placed into correct quadrant If using a computer and not hand calculator, you will probably have to convert the RA and Dec into radians (degrees * 180/Pi) MPC Click this button to create an MPC report. See “The MPC Report Editor” on page 219 for information on reviewing and saving this report. Astrometry - Changing the Astrometry Solution The above screen shot shows a bad astrometric solution generated by selecting the wrong star on the chart for one of the two stars in the manual method. This is indicated not so much by the number of stars used but by the standard deviation values (S.D.) and number of stars with color-coded residuals. When the results are this bad, try rematching the chart. Use the manual method if this was the best the AutoMatching routine could do even after checking the Configuration settings. This will not be an exhaustive discussion on the theory of the reduction process, which is based on an article that appeared in the 1990 July issue of Sky and Telescope that gives detailed instructions and other sources. This section covers the basics of Canopus' implementation of those methods. The M-C residuals are provided as a safety check of the derived position (you may have measured the wrong "star" or a dust spot). You should not use them to guide you as to when you have achieved the best results. The values in the Residuals table and the standard deviations should be the standards for determining whether you have a "good" position. There are no solid guidelines but if you can reliably achieve standard deviations of less than 0.3 arcseconds, preferably 0.2 arcseconds, you are on track. If using the MPOSC3 or UCAC catalogs, 02 arcseconds is often the upper limit of the residuals and 0.1 can be achieved with some minor “tweaking” of the results. 61 Changing the Reference Star Set You can change which stars are included in the astrometric solution. Each time you add or remove a star from the solution, Canopus automatically re-computes the residuals and standard deviations based on the new astrometric solution. Color Coding To make reductions go faster, the RA and Dec residual columns in the Data Table are color-coded. Color Status Criteria White Good Both the RA and Dec residuals are < 0.25 arcseconds. Silver Not Used The star has been eliminated from the calculations. Both residuals are set to 99. Yellow Active Row The active (current) row if the status is Good or Not Used. If the status is Fair, Poor, or Bad, the row keeps its status color, even when active Green Fair The RA, Dec, or both residuals are in the range of 0.25-0.39 arcseconds Blue Poor The RA, Dec, or both residuals are in the range of 0.39-0.74 Red Bad The RA, Dec, or both residuals are 0.75 arcseconds or greater Text is black when the line is white, yellow, or silver. If the line is red, green, or blue, the text is white when the row is not the active row. If a red, green, or blue line is the active row, the text changes to bold and yellow. If a large number of stars are blue and red, it could be that you misidentified one or both stars in the two-star alignment process or that one or both have bad catalog positions. Try re-matching the chart to the image. If the result of AutoMatching and nothing you do with the Configuration settings improves the situation, try manually aligning the chart and, if absolutely necessary, using the full manual method. If manually aligning the chart, manual or semi-automatic method, try using a different pair of stars for alignment. It doesn't always help but in some cases, it has made the difference between having 5-8 reference stars and having 1520 reference stars. See the “Astrometry” chapter in the Users Guide for a tutorial on removing “bad” stars from the solution set. Creating an MPC Report The MPC button allows you to send selected data to a disk file as an MPC compatible report. 62 Canopus has been "internationalized", meaning it will accept the comma (',') for the decimal point in those countries where this is the standard practice and Windows has been set to this option. While the Print option respects the Windows settings in this regard, the reports generated by the E-mail option always use the period ('.') for the decimal character. See the “Astrometry” chapter in the Users Guide for a tutorial on generating MPC reports and “The MPC Report Editor” on page 219. Locating and Measuring Other Asteroids It’s very possible that your images for a given asteroid from the same night may have one or more asteroids in the field. It may be possible even if you’re working a variable star. The Moving Object Search can locate and automatically measure any moving objects in the field but if you want to do a quick check and manually measure only those found objects for which you can get a good position, “there’s an app for that.” Here’s a screen shot of a field where 5987 Edithlevy was the primary target. Using the Locate Asteroids method, you can see that several others were in the field the whole time or were coming and going for the six hours after the mid-time of the image. The Users Guide contains a detailed tutorial on using this feature. The basic steps are: 1. Load and AutoMatch an image 2. Right click over the image and select Other Asteroids | Locate from the popup menu. 3. Wait for the search to finish and see what is shown. 4. Manually measure objects that you want to report to the MPC 5. Save the astrometry data and generate the report. Only the MPCORB file is used to scan for objects. This means that comets, with rare exceptions are not included. 63 64 Photometry - Overview The photometry side of Canopus is written primarily for lightcurve analysis and so many of its features are designed towards that end. Some of the methods used are different for asteroids than for variable star work but Canopus handles both. The concepts are a bit involved but, with a little practice, should soon be familiar. The general method of photometry is handled first, with occasional references to the more specialized work required for lightcurve determinations. Afterwards, the specifics required for lightcurve work will be covered. A complete discussion of good photometric technique is beyond the scope of this document. Astronomical Photometry: A Text and Handbook for the Advanced Amateur and Professional Astronomer, co-authored by Arne Henden and Ronald Kaitchuck, is an invaluable resource and should be in the library of anyone doing photometry. Also recommended is A Practical Guide to Lightcurve Photometry and Analysis by Brian D. Warner (me!, not the other Brian Warner of the University of South Africa and cataclysmic star fame or the musical one aka “Marilyn Manson” – Have I gotten strange phone calls in the middle of the night!). A Practical Guide is available from Springer and on-line book dealers (Amazon and Barnes & Noble) and provides more in depth coverage of the methods for obtaining and interpreting data to find lightcurve periods and amplitudes for asteroids and variable stars. The Users Guide The Users Guide “Photometry” chapter includes an overview of photometry principles in Canopus as well as a number of tutorials. That overview will not be repeated here. Please refer to the Users Guide. Some Definitions Lightcurve A lightcurve is a plot of magnitude versus time or phase versus time. Lightcurve parameters define the period of the lightcurve and the amplitude. For asteroids, the overall (maximum) amplitude is sometimes variable, due to seeing the asteroid along the axis of rotation at one opposition while broadside to the axis at another. Assuming a typical bimodal curve, with two maximums and two minimums, the amplitude between adjacent extrema may not be the same. Think of a “spud in space” (spinning potatoes are a good analogy for asteroids). As the spud spins, you see different areas presented and so the reflected light varies in intensity. If it’s a really odd potato (one for the Guinness Book, then the “lightcurve” for it may be far from regular). For any of these reasons and more, you’ll sometimes see a range of values listed for the amplitude of an asteroid’s lightcurve. Session In Canopus, a session is a group of observations that that have the following in common: Target Filter Comparisons star set Date Telescope/Camera To qualify a little more, the Date requirement does not allow for mixing observations made in the morning of one date and the evening of that same date. The idea is a continuous set of observations made without interruption (presuming clouds don't get in the way). For a fast-moving asteroid, you might have several sessions during the course of the night since you may be required to use a different set of comparison stars as you keep up with the asteroid's motion. The Users Guide goes into more detail about sessions. The Basic Steps Here’s a general outline of how you would go about measuring a set of images for period analysis, not including using PhotoRed for converting to standard magnitudes. 1. Make sure the configuration settings are correct with respect to the images to be measured and charting orientation required for AutoMatching. 65 2. Open one of the images to be measured and AutoMatch it. This establishes the Magnitude/Intensity Relationship. This is not required and can be side-stepped. 3. If necessary, use the Blinker to locate a moving object. 4. Open the Sessions form and create a new session. 5. Open the Lightcurve Wizard to indicate the comparison stars and target. 6. Select the images to be measured. 7. Use the Image List to measure the images. 8. Go to the Photometry Page and set the period search parameters. 9. Compute the initial period, analyze the results, and - if needed - refine the period solution. Photometry Tutorials What follows are the specific details about various forms and their entry fields. The process of using those forms is left to the Users Guide. It is strongly recommended that you work your way through the tutorials instead of trying to pick up things from this Reference Guide. By working through the tutorials first, you’ll become familiar with the fundamentals much sooner and can then take your time exploring the Reference Guide for fine details about various aspects of photometry. You’ll find the Users Guide in the \MPO\DOCS directory as an Adobe PDF. 66 The Sessions Form The Sessions form consists of three pages. The Sessions Data page, which allows entering new or editing existing data for a session. The Observation page, which displays the observations associated with the given session. The Comparison plots page, which displays plots of the raw or averaged data for each comparison star. The Sessions form also allows you to export and import data from other observers or another machine on your network. See Photometry Data Management on page 121 and the tutorials in the Uses Guide. Sessions Form - Session Data Concepts The following describes some specific entry fields or concepts on the Sessions form. Before creating a session, you need to understand some of the inner workings of Canopus that allow it to match data from one session to the next. Without understanding these concepts, you can get very lost very quickly. DeltaComp DeltaComp is short for Delta Comparison Star and is used to adjust the “zero point” for each session so that the net effect is that all observations were made against a common set of comparison stars. Differential photometry is based – naturally – on the difference between a comparison star and the object being measured. Depending on the method chosen, either the average of several comparisons is subtracted from the target’s magnitude (the Instrumental mode described in the Users Guide) or each target-comparison pair is handled individually with the average of the results used to form a single value for the target (the DerivedMags mode in the Users Guide). In asteroid lightcurve work in particular the same comparison stars are rarely used from one session to another. In fact, that’s the general assumption that Canopus uses as the need for and definition of sessions. Almost without exception, the average value of the comparisons, disregarding any errors, will not be the same from session to session. Even with standardized magnitudes, there can be a difference of a few hundredths of a magnitude from one session to the next. Even this small difference can make a big difference when trying to analyze data. The DeltaComp value in the Sessions form can be changed to move the data “up or down” until it merges with the data from another session. For those into details, the target’s magnitude is computed one of two ways. 67 Instrumental Mode Delta = (CAvg + DeltaComp + MagOff) – ObjMag CAvg The average value of the comparison stars for the given observation. DeltaComp The DeltaComp correction to match the CAvg value to the CAvg value from another session. MagOff The compensation for the target’s natural change in magnitude due to changing earth/sun distances. This applies to moving objects, not variable stars. ObjMag The measured magnitude of the target DerivedMags Mode MT = Average(Sum(mt-mc1 + Mc1.. mt-mcN + McN)) + DeltaComp + MagOff MT mt mcN McN DeltaComp MagOff Derived magnitude for the target Instrumental magnitude of the target Instrumental magnitude of comparison N Catalog magnitude of comparison N The DeltaComp correction used to compensate for catalog inaccuracies and measurement errors. The compensation for the target’s natural change in magnitude due to changing earth/sun distances. This applies to moving objects, not variable stars. How the MagOff value is computed is discussed in the following sections. EMag EMag stands for “Estimated Magnitude” and is of concern primarily for asteroid observations. As the asteroid moves in its orbit, its distance from the sun and earth is constantly changing. This alone means the asteroid is not the same brightness every night. In addition, as the phase angle for the asteroid approaches 0° (at perfect opposition), the brightness of the asteroid doesn’t follow the simple geometrical formula. This is known as the “opposition effect.” Canopus uses the EMag value to compute the adjustment required to match each session’s data based on this factor alone. The DeltaComp value should be independent of this error, accounting only for differences in the comparison stars. However, the calculation of the estimated magnitude may not be correct for one of many reasons (see below) and so the DeltaComp adjustment is used to “absorb” the error. The estimated magnitude is determined by using the orbital elements of the asteroid, which include the H and G values, to compute the estimated magnitude of the object down to 0.01m. The EMag value for the first session in a series of sessions is taken as the base value. The differential magnitudes in subsequent sessions are adjusted by the difference between this base value and the estimated magnitude for each additional session. This is not a perfect solution. If the H value (absolute magnitude) is wrong, there is a simple offset for which the DeltaComp value can be used to make the data match. The G parameter is another matter entirely. This describes the change in behavior of the pure geometrical magnitude formula based on the phase angle of the asteroid. It is not a linear function, is dependent on the surface structure and composition of the asteroid, and, to make matters worse, it is assigned a default value of 0.15 when G is not known. This is a bad assumption considering some asteroids have a negative G value. Despite these limitations, using the EMag value at least tries to adjust the differential magnitudes so that the need to work with the DeltaComp value is dependent more on the comparison stars than any other factor. Reduced Magnitudes When using DerivedMags in Canopus (and Transformed and Transformed Absolute), you are given the option of computing and using “reduced magnitudes”. Instead of using the distance for the first session as a reference point for 68 correction, all data are converted using the “unity correction” of –5 * log(rR) where “r” is the asteroid-Earth distance and “R” is the asteroid-Sun distance in AU. When taking this approach, the change due only to changing phase is computed independently. The reason for this option is both for keeping those corrections independent and to avoid some confusion when plotting data. The magnitudes in the plot will not match the sky magnitudes (the brightness of the object measured directly from an image using the M/IR). This is because of the corrections that are applied to keep the data as if it were all taken on the same night using the same comparisons. DM – and DM + These fields display the averaged change in magnitude over the previous 24hr (DM–) and following 24hr (DM+). These allow correcting differential magnitudes on an observation-by-observation basis due to rapidly changing geometry such as when a Near Earth Asteroid passes close to Earth. The corrections are calculated based on the central time given in the Mid Date/Time fields versus the actual observation time. These additional corrections can be critical in order to "de-trend" data that would otherwise show an artificial increase or decrease in differential values because of the object's rapid change in brightness during a close encounter. G This is the phase slope parameter. It is used in a complicated formula to compute the estimated magnitude of the asteroid. That formula also takes into account the opposition effect, which causes an asteroid to brighten more than simple geometry would say when near opposition. You must use the same value for G for all sessions on a given target. It may be possible to get a better solution during period analysis – to get the data to fit better – by changing the value of G. Canopus can automatically compute this value for an asteroid (see below). If the target is an asteroid, do not enter a value. Phase This is the phase angle at the time of the session. The phase angle is the apparent separation of the Sun and Earth as seen from the asteroid. So, when the asteroid is at opposition and directly on a line joining the Sun and Earth, the phase angle is 0°. The phase angle for the first session becomes the “reference point”, meaning that all observations are corrected to make it appear that all data were taken at the same phase angle. This can be critical if the first phase angle is < 7°, which is when the opposition effect starts to affect the brightness of an asteroid. Canopus can automatically compute this value for an asteroid (see below). If the target is an asteroid, do not enter a value. SDist and EDist SDist and EDist are, respectively, the distance of the asteroid from the Sun and Earth in Astronomical Units at the given date and time for the session. The EDist value is used to compute the light-time correction for an asteroid, making all time data independent of the distance between the asteroid and Earth. Why is this important? Say an asteroid was 1.0 AU from earth during session 1 and 2.0 AU from earth in session 2. The difference in light-time would be a little over eight minutes. Say the timing is for when a particular feature on the asteroid is at the center of the disk. In session 2, the light from that feature at the time it was on the central meridian would reach earth 8 minutes later than in session 1. In order to measure the real interval of time between successive crossings of the feature on the central meridian, Canopus must assume light travels at the speed of infinity. Since it doesn't, it must compensate for the differing light-times. Mathematically, this correction is stated TrueTime = ObservedTime – LightTravelTime Canopus can automatically compute this value for an asteroid (see below). If the target is an asteroid, do not enter a value in either field. 69 RA and Dec The RA and Dec fields are used for computing several values important to reducing data. They are, as you would assume, the Right Ascension and Declination of the object at the mid-time of the session. First, the RA and Dec are used to calculate the air mass of the object at the time of the observation. The air mass is required when using PhotoRed to reduce the instrumental magnitudes to standard magnitudes. It is more efficient to store this value in Canopus than import several fields into PhotoRed and have the latter compute the air mass itself. If the target is a variable star, the RA and Declination can used to convert the original date and time of the observation to heliocentric time, i.e., the time the light from the variable reached the Sun. By using heliocentric time, observations from different times of the year can be combined by eliminating the differences in light-times (up to 16.6 minutes). Canopus can automatically compute and enter the data for these two fields if the target is an asteroid. If the target is not an asteroid, you’ll need to enter the values yourself. How Canopus computes the asteroid position is covered later in this section. Important Note Concerning Julian Date Calculations As has been noted previously, Canopus converts the date and time in the original observations file into Julian Dates. It’s the JD values that are used in the lightcurve analysis and which must reflect the type of object being worked. Canopus has no way to tell if the session target is an asteroid or variable star, therefore it’s very important that you have the correct configuration setting before trying to find the lightcurve parameters from the data. If you have the configuration set so that Canopus does not compute Heliocentric JDs, then the value in the E. Dist field for each session is used to compute the light-time correction to the raw Julian Date computed from the observation data. If you have the configuration set so that Canopus does compute Heliocentric JDs, then the E. Dist field value is ignored and the correction is based solely on the RA and Dec values. In both cases, the RA and Dec fields are used to compute the air mass of the target at the time of the observation, based on the raw, not corrected, Julian Date. To change which correction Canopus applies to the computed Julian Date, set the “Heliocentric Times” checkbox on the Photometry tab of the Configuration form as needed. Sessions Form - Sessions Data Page This page is used to create new and modify existing sessions and import or export session data. It contains four main sections. The Sessions Table, which displays a summary of existing sessions. The table is read-only, so you cannot edit its data directly. To edit session information, you use the controls in the Session Data section. It will not be discussed in detail. 70 The Buttons Section, which features several buttons that start or perform a variety of tasks. The Session Data Section, which allows entering new or editing existing data. The Comparison Section, which is a continuation of the Session Data section and handles information about the comparison stars used by the sessions. The comparisons are those stars used for differential photometry. To Find an Existing Session To find a previously created session by the object’s name (or portion of the name), click on Sessions Table at the upper left of the form and then press <Ctrl+F>. This displays a search form. Enter the name or portion of a name for which to search and then click the OK button. Canopus searches the Object field and if any portion matches the entry, repositions the Sessions table to that session. To continue searching, press <F3>. If there are no more matches, the Sessions table is positioned to the last session. The search is not case-sensitive, so “Tchantches” or “TCHANTCHES” would find sessions with and Object field of “Tchantches”, “Tchantches (4440)”, “4440 Tchantches”, etc. To search by session number, press <Ctrl+G>. This displays a similar input form where you enter the session number. If such a session exists, the table is repositioned to it. If not, the table stays on the current session. To Filter Sessions To see only those sessions with the same object name, highlight one of the sessions for that target (click on it in the table). Press <Shift+Ctrl+F>. The table background turns green to indicate that you are viewing filtered records. To remove the filter, press <Shift+Ctrl+F> again. Batch Editing the Phase Slope Parameter (G) The value of the phase slope parameter, G (described below), can affect the results of a period search. It is possible to change the value for G for all sessions involving a selected object in a single process instead of manually editing each session. The button next to the G entry field in the Session Data section is used to invoke the batch editing feature. See the Users Guide for a tutorial on using this feature. All sessions for a selected object must use the same value of G. 71 Batch Editing the Mag Band Setting The “Filter” field on the sessions form, described below, indicates which filter was used to make the observations. It does not necessarily indicate the photometric band of the magnitudes for the comparison stars (also described below). For example, you may use a Clear filter but, since there is no such thing as a Clear photometric band, you used V magnitudes for the comparisons. The button next to the “Mag Band” drop down list allows you to change the photometric band for all sessions involving a specific object. See the Users Guide for a tutorial on using this feature. Buttons Section This section is used to start the process of creating or editing session data. New Click this button to create a new session. The controls in the Session Data section are enabled so that you can enter data. Canopus automatically fills in some information, using the most recent session (based on session number). This button is disabled when entering session data. See Entering Session Data below. Edit Click this button to edit the data for the highlighted session in the Sessions Table. The controls in the Session Data section are enabled so that you can enter data. This button is disabled when entering session data. See Entering Session Data below. Delete Click this button to delete the highlighted session in the Sessions Table. You will be asked twice to confirm this decision as the observation data associated with the session and the session data are permanently removed from the database. There is no undo for this operation. This button is disabled when entering session data. To File Click this button to send all data associated with the highlighted session in the Sessions Table to a text file and/or to two data files. Those two files comprise what is called a Saved Session set. OK Click this to close the form and make the highlighted session the current (or active) session. Cancel Click this to close the form and keep the current session as the active session. See “Working with Saved Sessions” on page 113 for more information. 72 Sessions Form - Entering Session Data This page is used to enter the core data for the session. When you start a new session and if there are previously created sessions, Canopus automatically fills in several of the fields based on the last session. It also fills the list of the Object, Telescope, and Camera drop down lists with up to the eight most recently entered unique items. This allows you to quickly select these items and so assure the entry is identical to previous entries. This is of critical importance with the Object field since Canopus groups sessions by the value in that field. In addition, Canopus stores the entry in the focal length field in the record from which each item in the Telescope list was obtained. So, when you select a previously used telescope, the focal length is automatically changed. You can, of course, change the value if necessary. Finally, when a new session is created, the COMPX fields are filled with A, B, etc. and the associated USE checkbox is automatically checked. This is so you can save the session without an error, even if you haven’t determined which stars are to be used for comparisons. When you use the Lightcurve Wizard, these entries are updated automatically to reflect the number of comparison stars selected in the Wizard. See the section on using the Lightcurve Wizard. The “Photometry” chapter of the Users Guide covers entering data into the sessions form. This section provides additional details about the individual fields and controls. New/Edit Mode only Buttons Save Click this button to save all changes and to exit edit mode. Revert Click this button to cancel all changes (except air mass calculations) and exit edit mode. Regardless if creating a new session or editing an existing one, the fields in this and the Comparison and Reference Stars sections have the same meaning and purpose. Session Data Fields / Buttons (New/Edit Mode only) Session This is a sequential number assigned to each new session by Canopus and cannot be changed. For those familiar with database programming, this is an auto-increment field. Object Use the drop down list to select from one of the eight most recently entered names or type in the name of a new asteroid, variable star, etc., for which the session is created. The program uses this field value to find all sessions for a 73 given object. While the search is not case sensitive, be sure to use the same spelling (including spaces, punctuation) in all sessions involving the same object or they won’t be found when trying to determine a lightcurve period. Select from the list when possible since this assures that the entry in this field matches those from previous sessions for the same object. Mid-Date Enter the date (UT) for the approximate middle of the set of observations yyyy/mm/dd format. Use leading zeros if necessary. This field is used to compute the asteroid's distance from earth and predicted magnitude as well as the RA/Dec of an asteroid. If observing variable stars, you should still enter the date, for reference purposes if nothing else. Mid-Time Enter the time (UT) for the approximate middle of the set of observations in hh:mm 24-hour format. Use leading zeros if necessary. This field is used to compute the asteroid's distance from Earth and predicted magnitude as well as the RA/Dec of an asteroid. If observing variable stars, you should still enter the date, for reference purposes if nothing else. Canopus reads the FITS header of the image open, if any, when the sessions form is started and automatically sets the date and time to the UT for local midnight based on the longitude setting in the configuration (so, Daylight Saving is not considered). If it cannot read the header or no image is open, the date is set to the current date and the time to 00:00. Filter Select the filter or equivalent from the list in the combo box. B V R I C Blue Visual Red Infrared Clear SG SR SI SDSS g’ SDSS r’ SDSS i’ This indicates which filter, if any, was used to take the image (use Clear for unfiltered images). This field is used to help group observations when imported into PhotoRed and when selecting sessions for computing lightcurve parameters. If you select ‘C’ (clear), a popup form may appear (depending on the setting of the “Mag Band” field). Use this form to select the “Mag Band” setting, which cannot be ‘C’ since there is no such thing as the Clear photometric band. Always set this to the actual filter used, not the photometric band for the comparison stars (see below). The “Mag Band” drop down list is used to indicate the photometric band. SDSS is the Sloan Digital Sky Survey. While one could store SDSS data under the near Johnson-Cousins equivalent, e.g., R instead of r, the differentiation makes for better record-keeping. Mag Band Select the photometric band or equivalent from the list in the combo box. This indicates the photometric band for the comparison star magnitudes and is not necessarily the same as filter. For example, if you used a Clear filter but selected V magnitudes for the comparison stars, you would set “Filter” to ‘C’ and “Mag Band” to ‘V’. If you attempt to select ‘C’ for this field, an error message appears since there is no such thing as the Clear photometric band. The field is reset to the “Default Filter” on the Configuration | Photometry tab. 74 Delta Comp If creating a new session, leave this value at 0. If editing the data and you changed which stars are used for comparisons, you need to recalculate this value. Click the "Calc DC" button to re-compute the DeltaComp. If there are observations associated with the current session, Canopus switches to the Observations page and re-computes the differential magnitudes, and displays the new differential values in the lower table on that page. If the computed DeltaComp value is different from what was previously entered, you’ll see a warning message. Click “Yes” to accept the new value. Click “No” keep the old value. This message is shown so that you don’t automatically lose the DeltaComp that was found during lightcurve analysis that allowed the session data to match other sessions. E. Mag If the target is an asteroid, click the "Calc M/D/P" button. This displays the asteroid selection form. Locate the asteroid, searching by name or number. Make sure the highlight is on the correct asteroid before clicking the OK button. G This is the phase slope parameter, which affects the estimated magnitude and DM ± values. Usually you will accept the default value from the MPCORB file, which is displayed in the label below the field as you scroll through the table. If the MPC value is not 0.15, the label turns red to warn you that you should use the MPCORB value instead of the default of 0.15. If you do not use the default of G = 0.15, you must use that alternate value for all sessions involving the same object. Do not mix values of G. See the Users Guide for a tutorial on the batch editing feature that allows you to change the value for G for all sessions involving a selected object. OK Click this button to have Canopus compute values for the Sessions form. If you click OK, the values in the EMag, SDist, EDist, G, Phase, RA, and Dec fields are updated. Cancel Click this button to close the form without calculating values. If the object is a variable star, do not use the asteroid look up. Doing so will put “artificial” values in the E. Mag, S. Dist, and E. Dist fields and will override the RA and Dec fields. Since the RA and Dec fields are used 75 to compute the target’s air mass and Heliocentric Julian Date, it’s important that the values in these two fields be correct. If the target is a variable star, enter 0 for this field so that no additional correction is applied to the differential magnitudes. DM – and DM + These fields display the averaged change in magnitude over the previous 24hr (DM–) and following 24hr (DM+). These allow correcting differential magnitudes on an observation-by-observation basis due to rapidly changing geometry such as when a Near-Earth Asteroid passes close to Earth. The corrections are calculated based on the central time given in the Mid Date/Time fields versus the actual observation time. These additional corrections can be critical in order to "de-trend" data that would otherwise show an artificial increase or decrease in differential values because of the object's rapid change in brightness during a close encounter. S. Dist and E. Dist These two fields are the distance in astronomical units (AU) of the object from the sun and earth, respectively. When the target is an asteroid, these values are used to correct the time and date of the observations to a common reference, i.e., the time the light left the asteroid and to compute a “unity distance” factor that is used to correct observations. In the case of E. Dist alone, the correction to the time of the observation can be critical since periods are reported to 0.001 h and higher precision. If the asteroid is 0.25 AU farther from earth in one session versus another, the difference in travel time for light is about 2 min (0.033 h) longer. This is greater than the usual reported error in the period. If the target is an asteroid, use the asteroid lookup (described above) to compute this value. If the asteroid is not available in the database, use another source, such as the MPC web site, to determine the object’s sun and earth distances and enter the values manually. If the target is a variable star, or if importing data that has already been corrected for light-time, enter 0 in both fields. G and Phase These are, respectively, the phase slope parameter for the asteroid and the phase angle of the asteroid at the time of the session. If you are not working an asteroid, do not enter values in these fields. It is better to let Canopus enter these values by using the “Calc M/D/P” button in order to assure that the correct values are entered. The value of G can affect period analysis. You can set all sessions for a given object to use a specific value of G to determine how the different value affects the period search results. See the Users Guide for a tutorial on using this batch editing feature. RA and Dec These two values are the approximate position of the target at the middle of the session. Enter the RA in HH:MM format, using leading zeros if necessary. Enter the Dec value in ±DD format, using a leading zero if necessary. Higher precision is not required since the effect on the computed air mass or Heliocentric JD is minimal. If the target is an asteroid, use the asteroid lookup (described above) to compute this value. If the asteroid is not available in the database, use another source, such as the MPC web site, to determine the object’s magnitude and enter that value here. If the target is a variable star or other fixed object, enter the approximate RA and Declination manually. Telescope Use the drop down list to select from one of up to eight entries from previous sessions or type in the description for a new telescope setup. This field is for informational purposes. 76 If you select from the list, the Focal Len field is updated to show the focal length that was used the last time the given telescope entry was used. You can change the value in the Focal Len field if required by typing in the correct number. Focal Len Enter the focal length of the telescope in inches or millimeters. This field is for informational purposes only. For consistency, always uses the same unit of measure. Camera Use the drop down list to select from one of up to eight entries from previous sessions or type in the description of a new camera and/or film. This field is for informational purposes. Temp Enter the temperature at which the images were taken. The field is for informational purposes. This is more important for CCD work as the sensitivity and noise of the camera is highly dependent on the temperature of the chip. Exp Enter the exposure time, in seconds. This field is for informational purposes. Canopus attempts to read the FITS header of the image open, if any, when the sessions form is started. If possible, Canopus enters values from the header for Focal Len, Temp, Exp. Confirm these settings, especially if the open image is NOT one of those to be measured for the session being created. Comp #1-5/CM/CI/Use Enter the catalog or user defined name for each star used as a comparison in differential photometry in the edit fields. The “CM” fields are the catalog magnitudes for the comparisons. These are required if using DerivedMags for photometry. The CI mags on the subtab are the color indices of the comp stars and target. Check the Use checkbox if the star is to be used in the calculation of a mean comparison magnitude. If you are creating a new session, these fields are filled in with A, B, etc. and the check boxes are checked. Using the Lightcurve Wizard automatically updates these fields with the RA and Declination of the comps, providing you did an AutoMatch before running the wizard. The CM values can be filled in automatically if you use the Comp Star Selector in the Lightcurve Wizard. See the Users Guide “Photometry” chapter for tutorials on the sessions form, lightcurve wizard, and comp star selector. You should have at least two comparison stars entered and marked as used. Using a single comparison star is not a good idea since it might be variable. Having at least two stars helps avoids this error and filter out random variations in the differential magnitude values by using the average of more than one comparison star. Transfer The Transfer button is used to move comp star data to and from PhotoRed so that you can apply transform corrections on-the-fly. The Users Guide explains this in more detail. Briefly, you transfer the comp star color index values obtained by using the Comp Star Selector to PhotoRed. The color index values are used to find improved catalog magnitudes for the comp stars that are transferred to Canopus using the Transfer button. Then, whenever you do a period search, you can apply the corrections on-the-fly. The reason behind all this is to reduce the need to change the DeltaComp value to get sessions from multiple nights to line up vertically, i.e., use the same zero point. 77 Notes Click this button to display the Notes editor. This is a simple text editor that allows you to include additional information and comments about the session. The data is included when the session is exported to a text file. The Comp Star Selector can add important information to this field automatically. See the Users Guide photometry tutuorials. If you followed the general steps correctly, specifically that you matched an image to a chart before creating a session, Canopus automatically enters data about all the stars used in the M/IR for you. OK Click this button to save the information in the editor. The changes are not fully recorded until you save the entire session. If you cancel the edit for the session, then you’ll lose the changes you made in the editor even though you “saved” them here. Cancel Click this button to close the editor without saving any changes. Editing the M/IR after creating the session does not modify the values already entered in the Notes editor. You should make sure to set the M/IR before creating the session so that the information in this field reflects the correct information. Transferring CM/CI Data From the Notes Field If you used the CompStarSelector (see the section on photometry and the Users Guide) and transferred the comp star data to the Notes field and/or you saved the comp star data to a text file, you have the CM and CI data available to import into those fields. If you transferred the data directly from the CompStarSelector, this step is not necessary. However, later versions of 9.5, while they did have the CompStarSelector, did not offer the transfer option but you could save the data in a text file. To import the data for the comps of a given session, right click over the sub-notebook that has the CM and CI entry fields. This displays a popup menu that allows you to import the CM values and either B-V or V-R color index values into the fields from the NOTES field or the separate text file. This saves you having to manually enter the values. When you do import the data, the DeltaComp value should be set to 0.00 (or something close, allowing for a slight adjustment). You are presented with a confirmation message asking if you want to reset DeltaComp to 0.00. Generally, answer “Yes” unless the value is already close to 0.0 (|DeltaComp| < 0.1). 78 Sessions Form - Observations Page The Observations Page displays data for the observations associated with the session being edited. The Observations Table shows the raw data taken from the images as measured by Canopus. The Calculations Table shows the results of the differential photometry calculations. The Observations Table Save for one column, “Use” at the far left of the table, the data in this table cannot be edited directly. Use The first column in the table is an editable checkbox. If the box is checked, the observation is used in the differential magnitude calculations. If the box is not checked, the observation is ignored. This feature is handy when you encounter noisy data or when you measured images where the asteroid was passing near a star but didn’t realize such until after the fact. You can remove those “contaminated” observations by unchecking the box. Date/Time This is the date and time taken directly from the image header. It is not necessarily the Universal Date and Time. Using the actual header times makes it easier for you to match an observation to a given image. Canopus converts these to Universal Date and Time when performing internal calculations. For this reason, you must be sure of the Configuration settings that equate the image header date and time to UT date and time. Air Mass This is the computed Air Mass at the time of the observation. Canopus calculates the value at the time the observation data is first recorded using the Lightcurve Wizard and the value is passed to PhotoRed for accurate transforms to standard magnitudes. The correct calculation of this value depends on correct Configuration settings, specifically the longitude, latitude, and UT offset values. Also critical is that the values in the RA and Dec entry fields in the Session Data section on the Sessions form are correct for the time of the session. If you had the incorrect settings when you first added data to the observations table, there is a way to fix the problem. See the description for the Air Mass button. ObjMag and ObjIMag These two columns display, respectively, the derived magnitude for the target based on the Magnitude/Intensity Relationship (M/IR) and the instrumental magnitude as computed by Canopus. The calculation for the instrumental 79 magnitude uses the eADU setting on the Configuration General Page and the normalized intensity of the star data, i.e., as if the exposure was 1-second long. Normalizing the intensity is required to account for a variety of factors, the most common of which is that when doing filtered photometry, the exposure for images taken through one filter may not be the same as the exposure for images taken through another filter. The differing exposures are usually required to maintain a minimum SNR ratio. Comp1–5Mag and Comp1–5IMag As with the ObjMag and ObjIMag, these columns are the derived and instrumental magnitudes. Canopus uses a value of 99 to indicate the star was or could not be measured. The Calculations Table The Calculations Table shows the results of the differential magnitude calculations and allows you to quickly match a given observation in its list to one in the Observations Table. Whenever you click on a line in the Calculations Table, the entire line is highlighted and Canopus repositions the Observations Table so that the observation corresponding to the line in the Calculations Table is highlighted in the Observations Table. Again, the date and time are those taken directly from the image header and are not converted to Universal Date and Time. Editing Data Excluding/Including Observations To exclude an observation, click on the table on that record. Move the active cell in that row to the Use column and uncheck the box by clicking on the ‘X’ or pressing the space bar. To restore an observation, click on the cell or press the space bar again. Add/Subtract Radio Buttons and Correct Button The Add/Subtract radio buttons, the time entry field, and Correct button can be used to correct the time of midobservation for each observation needing a constant offset. This avoids having to remeasure the images to get the correct times. For example, if the configuration settings were wrong and the times are for start of exposure and not mid-exposure, you can enter the offset (one-half the exposure time), and have all measurements corrected by that amount. You should, of course, change the configuration settings so that future measurements do not require a correction. The entry field is hh:mm:ss format, meaning you can enter corrections in the range of 1 second to 23 hours 59 minutes and 59 seconds. This feature does not correct the times in the FITS headers but simply applies a constant offset to all measurements. Clicking “Cancel” on the Session Data tab will NOT undo changes made here. To restore the original values, you must subtract (or add) the same value that was added (subtracted). Air Mass Button This button re-computes the air mass values for each observation. If you had the correct Configuration settings and RA/Declination on the Sessions form before measuring any images, it should not be necessary to re-compute the values. In case you did not have the right values or settings, you can correct the problem by first assuring those values and settings are correct and then using this feature. Re-computing the air mass values cannot be cancelled by using the Cancel button on the Sessions Data tab. Values Click this button to re-compute the differential magnitude between the averaged comparison star value and the object for each observation. 80 The only need for this button is to recompute the differential values after changing the DeltaComp value or adding/removing one or more comparisons from the calculations. Using the Calc DC button on the Session Data tab has the same action as this button but it also recalculates the DeltaComp value and, if you chose, replaces the old value with the new. Duplicate Data When adding data to the observations file, Canopus performs checks to avoid duplicate entries. This allows you remeasure images introducing new records. However, nothing’s perfect and you can end up with duplicate entries. If this happens, then when doing period analysis, the duplicate records are all included. If the data point is invalid (the target merged with a star) and you try to remove it from the calculations by clicking on its point on the period analysis plot (see Editing Data Using the Plot – pg 105), then only the first entry is excluded but not the second or any additional duplicates. This leads to confusion when plotting data because even though you’ve told Canopus not to include the point, it still shows up. You can remove duplicates with a simple set of steps. 1. Select the session with the duplicate observations in the sessions list. 2. Click the Edit button to edit the session data and observations. 3. Click the Calc DC button used to compute the DeltaComp value. Each time you compute the DeltaComp value, Canopus checks for duplicate records. The first of the two or more duplicate records is retained and all others are removed from the table, not just flagged. Sessions Form - Comparison Plots Page It’s a good idea to check on the comparison stars to be sure that they are not variable. This is the function of this page. You must click the “Calc DC” button on the Sessions Data page to generate the initial plots on the Comparison Plots page. Raw Data Click the Raw radio button to plot the data for the selected comparison star. The example above is not one of a variable comparison. It is the expected plot of magnitude vs. time and shows the comparison getting brighter as its air mass reached a minimum (the star reached the meridian). If the raw plot showed an opposite curve, i.e., it got dimmer as it approached the meridian, then that would be a problem. Note the “Scaling” is set to “Expand”. This exaggerates the vertical scale so that you can see small variations. This can make things seem worse than they really are. See below. 81 Averaged Data Click the Avg radio button to view the data for the selected comparison against the averaged magnitude for the other comparisons for each observation. This is somewhat akin to using the given comparison as the target and plotting the differential photometry against the other comp stars through the night. The above example shows a reasonably good night as the range of values is relatively narrow and there is no obvious trend. In some examples, this plot has shown a nice sinusoidal curve and so the star was not used for computing differential target values. There are two modes for displaying the averaged data 1/2 Mag The plot height is forced to one (or two) magnitudes with the averaged data near center. This view is provided for those who are more accustomed to seeing K-C plots on the same page as the full lightcurve. In most instances, the scale of the full lightcurve is much greater than needed for the K-C plot and so the K-C plot appears to be nearly a flat line. For those not used to it, the previous default Expand view seems to show a very large scatter in the averaged values. The two plots above represent the same data but give much different impressions of the scatter. Expand The plot height is set to an arbitrary amount to expand the vertical scale of the averaged data. A substitute for this is to use the zoom feature of the plot. See Period Determination - Changing the Data Plot View. The same plotting tool is used for the comparisons and full lightcurve and so the general instructions in that section work here. Note that when plotting the Average value, the plots include the standard deviation of the values for the selected comparison. In the screen shots above, the standard deviation was only 0.009 mag, indicating a minimum of scatter in the data for all of the comparisons. Remove If there are some obvious “bad” data points you can remove the observation from the calculations: 82 Click on any data point to review its date/time information, which appears in the status bar at the bottom of the page. To remove the data point, move the mouse cursor of the point and do a Ctrl+Click. This displays a confirmation message. Click YES to remove the observation and have the program automatically recompute the plot. Save Click Save to save the current plot. This displays a Windows file dialog. The file is given a default name of COMPX_<RAW/AVG>., where X is the number of the comp star selected. You can save the file in PNG or BMP format. Sessions Form – Catalog Check Page The checks on the “Comparison Plots” page show only the stability of the comparisons among one another. They do not show the quality of the DerivedMags solutions. For example, one of the stars may have a catalog value that is off by several tenths of a magnitude. This will increase the error in the mean of the DerivedMags value and can make it so the session doesn’t match other data – it’s on a different zero point. This feature can be used whether using Instrumental or DerivedMags but only if you transferred from the Comp Star Selector or manually entered the catalog magnitudes for the comparisons in the “CM” field so on the sessions form. Raw The screen shot above shows the Raw view of the Catalog Check. Here, the Y-values are the derived magnitude for the asteroid when using each one of the comparisons. In a perfect world, the plots would like exactly on top of one another since the derived magnitude for the asteroid should be the same regardless of which comparison is used. If the plots are not well-aligned, that indicates that, mostly likely, the catalog magnitude for the corresponding comparison is bad. 83 Average The average plot shows the data for each comparison as the difference between the derived magnitude using the selected comparison star catalog magnitude minus the average of the derived magnitudes for the object using the remaining comparisons. Here again, in that perfect world the plots would sit exactly on top of one another. The normal vertical scale is ±2.5 magnitudes, so these plots did appear to be superimposed until the zoom capability was used to expand the vertical scale. The data for comps 2-4 are reasonably close to being at the same level. Comp1’s data are about 0.06 magnitude below Comp 3. This slight mismatch could make this session be too high or low in comparison to another session. It would probably be best to drop Comp 1 from the calculations by unchecking its “Use” box on the “Session Data” tab. A dramatic example of how this feature can spot “bad” comparisons is shown in the screen shots below when working a different asteroid. Three comparison star data sets lie very close to one another but the one for Comp 2 is way below the others. With Comp 2 used in the calculations, the DeltaComp for this session had to be changed considerably from 0.00 to make it mate with sessions from the same night. When Comp 2 was removed, the session lined up perfectly with the others when DeltaComp was set to 0.00. 84 The Lightcurve Wizard The general idea of lightcurve photometry is that you measure the images of the target from a given session. When you measure the images of the target field, you want to also measure the brightness of at least one but preferably two to five comparison stars. These will be used in differential photometry, where the difference between the individual comparisons or as a group and the target are used to find a value for the target to be used in analysis. The Lightcurve Wizard in Canopus takes you through the steps of defining those comparisons and the location of the target in reference to one of the comparisons (the anchor star). By defining the target’s position in reference to the anchor star on two different images, Canopus can determine the objects motion (even if it’s not moving) and so “predict” where the target will be on any given set of image. You can manually step through the images or let Canopus do most or all of the work after running the Wizard. Even if doing things manually, you can still measure a night’s run in only a few minutes. The Users Guide contains several tutorials involving the Lightcurve Wizard and Canopus Image List. This section covers supplementary material to what’s in the Users Guide. StarBGone StarBGone! is a special feature of Canopus that subtracts selected stars from an image just before the image is measured. This feature is designed specifically for those working moving targets, such as asteroids, that cross over field stars during a night's run. Without StarBGone! those images where the target and star merged would have to be skipped, thus losing important data. StarBGone! setup is part of the Lightcurve Wizard and Image List. You do not have to pre-process your images since Canopus can merge flats, darks, and bias frames on-the-fly. StarBGone! Setup See the tutorial in the Users Guide for how to setup StarBGone! as part of running the Lightcurve Wizard. When setting the reference and subtraction stars in the Wizard, you must have the measuring apertures set to the same values that will be used when measuring images after running the Wizard. How StarBGone! Works The first reference star is measured independently in each image during the measuring process and scaled so that its intensity is the same as a given subtraction star. This scaling involves not only matching the overall intensity, but doing it on a pixel-by-pixel basis via a “map” of the reference star. This allows Canopus to account for the shape of the reference star which may go from round to out-of-round from image to image due to tracking errors, bad seeing, etc. The adjusted reference star is then subtracted from the location on the image where the subtraction star is found. Once all stars have been subtracted, the image is measured. Since only the intensity due to the subtraction star is removed from the image’s in-memory buffer before subtraction, the intensity due only to the target is measured. The second reference star is used with the first to monitor changes in the orientation and scaling of the images, e.g., rotation due to imperfect polar alignment or focal length due to temperature changes. This allows placing the scaled reference star over the subtraction stars to sub-pixel accuracy. StarBGone! is not a cure-all that will fix every problem. Notably, it cannot correct situations where a star several magnitudes brighter than the target is involved, especially if the star is near saturation or in the nonlinear portion of the CCD response. On the other hand, StarBGone! can do wonders in many cases. In one test, where the asteroid crossed almost directly over a star, without StarBGone!, the combined magnitude increased by 1.2 mag. The same images using StarBGone! showed a 0.02mag variation. You should run tests on various sets of images so that you can determine the limitations of StarBGone! on your system. You’ll probably find that StarBGone! can handle a large majority of situations and that you’ll be able to recover data in many cases that were previously hopeless. 85 Handling Meridian Flip Those using German Equatorial Mounts (GEM) are familiar with the problem of the scope tube hitting the pier at some point during a night’s run. What they (or their automation software) do is to flip the scope to the east side of the pier around the time the field is near the meridian. This allows the scope to follow the field down to the western horizon. It also causes the orientation of the stars in the image to change. If using only a single pair of images to determine the X/Y motion of the asteroid (or offset of the fixed target from the anchor star), and you measure an entire night’s run as a single set, then somewhere during the measuring process the X/Y offsets are no longer going to be valid. This happens when the first image after the meridian flip occurred is loaded. That’s because the image is rotated and the fact that the X/Y offset of a given comp from the first star is a function of the angle between the two stars and their distance from one another on the image. The way around this problem is to break the measuring process into two steps but still use one and only one session. 1. Create the session in which all data will be recorded. 2. Run the Lightcurve Wizard, working only with those images before the meridian flip. 3. Measure that first set of images. 4. Do not create a new session but keep the one just used active. 5. Rerun the Lightcurve Wizard. A confirmation message appears saying that the current session already has data and wanting to know if you want to continue. Answer "Yes". 6. Use the first image after the meridian flip for Image 1 in the Wizard and a later image for Image 2. 7. You must use the same comp stars in the same order on the second pass of the Wizard as you used in the first pass. Measure the images from the post-meridian flip only. This puts all data into a single session using the same comparison stars. Some people note problems after a meridian flip, usually due to flat field issues, where the data from before and after the meridian flip do not quite line up even when using the same comparison stars. If you have this problem, the best solution is to break the night's run into two sessions, putting the data from before the flip into the first session and the data from after the flip into the second. Then you can adjust the DeltaComp value of the second session to match its data to the first session. Image Rotation If your polar alignment is not perfect, or you're using an AtlAz mount, the image will rotate about its center during the session. For a small polar misalignment, this rotation is often is insignificant and there is no need for worry. Regardless, Canopus automatically accounts for image rotation when using the Lightcurve Wizard and then measuring the images. The amount of rotation is determined by using the X/Y coordinates of the #1 and the comparison star among the others that is farthest away from the #1 star. The angle between the two stars is computed for the two images used in the Wizard along with the time between the two images. From these, the rotation rate is found. This rotation rate is applied to each image when placing the measuring apertures over the comparisons and target. Canopus chooses the second star automatically based on the first image and then attempts to find the same star on the second image used in the Wizard within a 10x10 pixel box around the expected position. If the rotation is so great or the field of view changes so much that the second star cannot be found, the rotation rate is set to 0 and Canopus cannot keep track of the actual rotation. If you encounter this problem, then re-run the Wizard and choose the second image and/or other comparisons such that the farthest comparison star can be found on the second image in the Wizard within ±5 pixels in X and Y of the expected position. 86 Note that the rotation corrections are based on the #1 star's position, i.e., the rotation axis is about that star and not the center of the image. This works because you can reset the position of the measuring aperture for the #1 star at will by clicking on it on the image. All other offsets are based on the position of that #1 star. Setting the Measuring Apertures Click the “Apertures” button on the Canopus top tool bar to display the Aperture Settings form. Not One for All Canopus allows you to set the measuring apertures independently for the target, comparison stars, and for astrometry (when doing an AutoMatch). This can be handy for those times when working a moving target and it’s trailed. In this case you an create an elliptical (or rectangular) set of apertures for the target, even rotating them to match the target’s motion, while keeping circular (or square) apertures for the comparisons. Aperture Settings Each set of apertures has three regions: the measuring aperture, dead zone, and sky annulus. Circular Check this box to use circular apertures, as shown in the screen shot immediately above. These have the advantage of including less sky within the measuring region but the disadvantage of dealing with partial pixels. Height/Width The Height and Width values set the dimensions for the measuring aperture, which is the inner region surrounding the target. The dead zone is a boundary, usually 1-2 pixels wide, that serves as a buffer between the region within the measuring aperture and that defined by the outer annulus, which is used to measure the sky background. These values do not have to be the same but each one must be an odd number, e.g., 7 but not 8. If they are not equal, this makes for an elliptical or rectangular set of apertures useful for working trailed objects. 87 Rotation The rotation angle is useful only if the height and width have different values for “circular” apertures (why rotate a circle). Square or rectangular apertures will show the effect of rotating the apertures. This features allows matching the apertures to objects that are trailed, usually because they are moving and not poor tracking. Dead This is the width, not radius, of the dead zone. This acts as a buffer between the measuring and sky background regions so that a pixel is not used in both. A good setting is 2. Sky This is the width, not radius, of the sky annulus. Pixels within this region are used to determine the sky background. That value is subtracted from each pixel in the measuring area to yield the final value for the target. Using the example above, the measuring aperture would have a diameter of 11 pixels, the dead zone would have a width of 2 pixels (or diameter of 15 pixels: 11 + 2*2), and the sky annulus would have a width of 11 pixels, making its diameter 37 pixels: 11 + 2*2 + 11*2. What Size Aperture? The best size for the measuring aperture depends on seeing and image scale. A good starting point is so that the region about 3-5x the FWHM of the seeing disc, e.g., if seeing is about 4 arcseconds, you need to use an aperture that corresponds to about 18 arcseconds. However, too small a region doesn’t measure all the data and too large measures too much sky, which quickly decreases the SNR value. The initial dead zone value should be 1 or 2 pixels. The larger value is recommended for circular apertures given the problem of partial pixels “poking their heads” into the sky annulus. A rule of thumb for the sky annulus width is about the same or a little less than the diameter of the measuring aperture. Try several sizes to see which gives you the most stable background reading. Tests in crowded fields, e.g., M67, showed that the background level varied by about 0.3% (0.003m) whether there were no stars or several stars in the annulus. Don’t go too small since that may not give enough of a statistical sample. Internally, Canopus assures a minimum number of pixels, about 80, regardless of the size of the annulus. However that may not be enough under many circumstances. If you cannot get a centroid value when measuring a star in a crowded field, you can often fix the problem by increasing the size of the sky annulus so that there are more sky-only pixels available. About Sky Background Calculation Finding a good sky background value is an art, one that is hard to master and has involved many schemes. In Canopus, the algorithm finds the initial mean and standard deviation of the pixel values within the sky annulus and then subtracts those pixels that differ by more than one standard deviation from the mean. It computes the mean and standard deviation again and starts over. This process is repeated until the mean before and after subtraction stabilizes to within 1% (0.01 mag), the standard deviation reaches a minimum level, or the number of pixels remaining in the calculation reaches 80. If that minimum count is reached and none of the other conditions have been satisfactorily met, the algorithm exits, indicating that it cannot find a valid sky background. 88 Too high a “Clipping” value in the configuration could cause Canopus to fail to find a valid background anywhere on an image (or only in limited areas) or fail to measure a star that, despite being near the background level, is easily seen on the screen. Using the Wizard The Users Guide has a detailed tutorial on using the Lightcurve Wizard and Canopus Image List to measure images. Please refer to the “Photometry” chapter in the Users Guide for details on using the Lightcurve Wizard. The Users Guide is found in \MPO\DOCS as a PDF. You will need Adobe Acrobat Reader 5.0 or later. This is a free download from www.adobe.com. The Comp Star Selector The Comp Star Selector (CSS) was introduced in later versions of 9.5. This feature allows you chose comp stars when doing differential photometry that are similar in color to the target. This improves the overall quality of the measurements since the comparisons and target will be affected about the same by changing extinction (remember that blue stars “fade faster” than red stars as the field gets closer to the horizon). You should always use the Comp Star Selector. The most important reason is that it records the catalog magnitudes of the comparison stars and can transfer those into Canopus so that they become available for using DerivedMags approach. If doing Instrumental analysis, the average of the comparison star catalog magnitudes can be used to set the nightly zero point for each set of data. Linking sessions via this approach has been quite successful in work on very long period asteroids. Finally, while you may hope to use TrueMags, those many external factors mentioned earlier may come into play such that non-differential photometry produces very poor results. With the DerivedMags approach, you still get catalog-based magnitudes that are much more reliable and stable. The benefits of the CSS are many and the extra time to set it up it is minimal. Use it! Using the Comp Star Selector is covered in the Photometry chapter of the Users Guide. What follows provides some additional information about specific controls. The CSS is invoked from the Lightcurve Wizard when working on the first image. Click the “Selector” to invoke the CSS. Catalog List Use the drop down list to select the MPOSC3, LONEOS, or User Star catalogs. Filter Select the filter band for which magnitudes will be used. This can be any band regardless of which filter was used to take the images so, for example, if using the Clear filter, you could pick V or R. Plot Comps Click this button to locate stars that have magnitudes for the selected band. 89 You must have done an AutoMatch just before invoking the Lightcurve Wizard on the same image that you designation as Image 1 in the Wizard. The plot shows the stars as catalog magnitude versus instrumental magnitude. You want a slope close to 1.0. If you click on a data point on the plot, Canopus highlights that star on the image. Likewise, if you click on a star in the image and it is included in the plot data, that star’s data point changes to a green square. If no data are available for the selected star, the green square from any previous “hit” is reset to a red circle and the status bar at the bottom is blanked out. This indicates that the star is not valid and should not be used for a comparison. Set Comp X Click this button to include the star that was just measured on the image. This adds the star’s information to an internal table and updates the table on the Comps tab. Solar / All These two radio buttons determine if all stars found during the AutoMatch are displayed when plotting comps or just solar-color stars (0.5 B-V 0.9). You can click either one after clicking “Plot Comps”, which builds an inmemory list of all stars. Selecting the “Solar” button simply filters the list while selecting “All” removes the filter. Show on Image / Force Hide The “Show on Image” checkbox and “Force Hide” controls are enabled only when the “Solar” radio button is selected. Check the “Show on Image” box to display circles around solar-color stars on the image. Uncheck the box to hide the circles. Selecting the “All” radio button also hides the circles, which cannot be shown when the “All” button is selected. The “Force Hide” button is used to reset the circles should they get out of sync. For example, if you have the circles showing and then invert the image, that removes the circles but the Comp Star Selector is not aware of that fact. When you click the “Force Hide” button, a message appears asking if the circles are being displayed. Answer as needed. The CSS then forces the circles to be hidden and the “Show on Image” box to the unchecked state. Comps Tab The Comps tab shows the data for the stars that have been measured and included in the set. If no magnitude is available for a given band, it is set to 99.990. The BVRI magnitudes are taken from the 2MASS to BVRI conversions by Warner (2007, Minor Planet Bulletin 34, 113-119). Comp Star Selector: Transferring Data to Canopus You can have the CSS transfer data to the current session so that you don’t have to do manual data entry. Avg. To Delta Comp Check this box if you’re using the “Instrumental” photometry mode in the Canopus configuration. This copies the average of the comp star magnitudes to the DeltaComp field in the sessions form. You must do this in order to help Canopus compensate for using different comp star sets in different sessions. 90 Leave the box unchecked if you’re using the “Derived” magnitudes mode (the preferred method), where DeltaComp should be 0.00 (or very close to it). Set Comp Mags Check this box to transfer the catalog magnitudes of the comps to the “CM” fields on the sessions form. This is for when using the “Derived” photometry mode on the Canopus configuration. Text to NOTES Check this box to transfer the contents of the memo field on the Comps tab to the “Notes” field in the current session record. Transfer Click this button to transfer the selected data to the sessions form and its underlying current sessions record. Save to Text Click this button to save the memo contents to a text field. While the “Text to NOTES” option saves the same information, it is not a bad idea to have some redundancy, especially if you are working in a collaboration and want to send the CSS data to your colleagues. Lightcurve Wizard - Remeasuring and Picking Up Later Should you decide to re-measure the images from a session at a later time, possibly using a different comparison or reference star set or a flat-field, or reload a previously measured image during a run through the image list, Canopus does not necessarily add a new record to the observations database. Canopus checks several values associated with the measured image before adding the data, this includes the date/time of the image and the session number. If it finds a match, then it replaces the original data with the new. If it cannot find a match, only then does it add a new record to the observations database. Picking Up Later Let’s say that after a few hours of imaging that you want to measure the images you have so far and, after measuring those images, you close the Images List. It is still possible to measure additional images without having to go through the entire process again, including re-measuring those initial images. You would do so by simply selecting Photometry | Set Image List and select images that you have not measured so far. Then run through the Images List form. As noted above, even if you do select images already measured, this won’t necessarily mean duplicated records. There are some rules to keep in mind if you want to pick up measuring images after an initial set. 1. Don’t get too anxious. If you don’t have a long enough run before starting, Canopus cannot extrapolate the target’s motion as accurately. You can reposition the target aperture by doing a Ctrl+Click on the target in the image, but you may have to do it several times. Another reason to wait is if the target is going through a field where you’ll need to use StarBGone! The more accurately Canopus computes the target’s motion, the more accurately it will place the track on Image 1 that shows the asteroid’s path. You use this track to determine which stars in the images need to be subtracted. 2. Don’t generate another chart from the measurements page. It’s OK to generate a Quick Chart but nothing else. Generating a chart on the measurements page resets the M/IR. If you’re using the M/IR derived magnitudes, then you’ll have to go back to square one. 3. Don’t change the default session. Doing so doesn’t reset the M/IR but if you forget to change back to the session you were using, additional data goes into the wrong session. At 3 AM, this is very easy to do. 4. Don’t rerun the Lightcurve Wizard. This overwrites the positions for the comparisons and target that you previously measured. 91 The exception to this is if you’re measuring a set of images after a meridian flip. In this case, you do need to re-run the wizard. What you won’t necessarily do is create a new session and so add the additional data to an already existing session. 92 Finding the Period of a Lightcurve The two primary parameters of a lightcurve are the period(s) and the amplitude. If working an asteroid, the period you’ll determine initially is the synodic period, i.e., the period from the successive times a given point is at the “central meridian” of the asteroid as seen from the earth. Only after determining the period over several apparitions, or at least large range of phase angles, can one make the more accurate determination of the sidereal, or true, period of rotation. Because any given asteroid might be seen broadside to its axis of rotation at one opposition and along the axis of rotation at another, the amplitude of the lightcurve may not be the same at each opposition. Many times you’ll see the amplitude of the lightcurve expressed as a range of values instead of one. This reflects the changing characteristics of the lightcurve due to the way the axis of rotation is presented to Earth. If your interest is variable stars, don’t be misled by all this talk of asteroids. Canopus is just as well suited for variable star work. When combined with PhotoRed, which converts instrumental magnitudes to standard magnitudes and has special routines just for batch variable star measuring, Canopus is a powerful tool for all types of research. The Users Guide has a set of tutorials covering period searching. This section will not provide detailed steps on the process but only additional insights to those offered in the tutorials along with more detailed explanations of the search options. It’s Easy to Be Hard If there is any one point to emphasize it’s that finding the period of an asteroid is not so simple as to get one night’s data and say that you’ve found the correct period, even if you get what appears to be one or more complete cycles. It may take many sessions to get enough data before you can say with some confidence that you have found the correct period. For a more analytical interpretation, to state the period to 1% precision, you must have data that covers reasonably a full cycle and has a total distribution over 3 revolutions. To get to 0.5%, that goes to 10 revolutions. 0.1% requires 30 revolutions. To say you found the period of a 6 h asteroid after a 7-hour run down to 0.01h is stretching things – a lot. Even if you do have enough data, there are many ways to be fooled. One possibility deals where two periods provide almost equally good solutions. Often these two periods differ by one-half or a full cycle per day, the usual observing cadence between observing runs. Matters are made worse if you get data sets several days apart. Here you can’t be sure exactly how many rotations occurred. In short, no matter how sophisticated the tool, it takes some intuition and even luck on occasion to find the period of an asteroid (or variable star). Don’t be fooled by “easy solutions” of any kind. It could prove embarrassing. You’ll find more details in “A Practical Guide to Lightcurve Photometry and Analysis,” which is listed in the References section. Period Determination – One or Two Periods? Recent years have seen a number of binary, and even multiple, asteroid systems being found. A single body lightcurve provides more than enough work but if the object is binary, there maybe two, possibly three periods involved. For an asynchronous binary, where the satellite has a different rotation period from the primary, there is, of course, the rotation of the primary (larger) body. If the satellite’s orbit is aligned just-so, there will be eclipse and occultation events, much like those seen with eclipsing binary stars. This is often called Porb, or the orbital period. The third possible period is the rotation of the satellite itself. If it is not tidally locked with the parent such that one revolution equals one rotation (like the Earth’s moon), then there may be a small amplitude curve that is due to the rotation of the satellite. This is often hard to see, if at all. Canopus’ period search routine has been modified to allow searching for the orbital period as well as that of the primary and secondary bodies. The following discussion presumes a single body with a single period. The Users Guide contains a tutorial that explains how to use the dual period search. 93 The dual period search function does not work with “tumbling” asteroids where the total of the two periods, rotation and precession, is not a simple addition of two curves but much more complex. Dual period searching is NOT easy or straightforward. You should be thoroughly familiar with single period searches on single body objects before you try your hand on binary systems. For more complete discussions on binary and tumbling asteroids, see the papers by Pravec et al in the journal, Icarus. Period Search Parameters The period search parameters are set on the Lightcurve Analysis page (<Ctrl+4>). Orders This is the number of harmonic orders in the Fourier analysis. If you have 25 or more data points that cover a good portion of the curve, a good starting value is 4. If coverage of the curve is sparse, e.g., large gaps, you may need to try a lower value such as 2. Min. Enter the minimum period, in the default base time, for the search. The default base time in Canopus is hours, which is more typical for asteroid work. Variable star periods are usually in days. You can select which base is used with the configuration settings. See “Configuration - Photometry Page” on page 38. Size This setting has different meanings for the three types of period searches. Reg The increment (in days or hours) between each trial period. The highest period is MaxPer = MinPer + (Steps-1) * Size. Orders This setting is forced to 1 regardless of the value entered. Auto Used to compute the maximum period in the same way as the “Reg” search. The actual step size increases in proportion to the trial period used in the previous step during a search. Steps This setting has different meanings for the three types of period searches. Reg The total number of trial periods to examine. Orders The highest Fourier order examined is Orders + Steps. Auto Used to compute the maximum period in the same way as the “Reg” search. The actual number of steps depends on the initial period and the total span (in days) of the data set. Bin Enter the number of adjacent data points to be “binned” to form a single data point for period analysis. The allowed range is 1 to 10. One means all points are used. For actual binning, a good initial value is 3. If the total number of data points is not evenly divisible by this setting, the “left over” points are still averaged to form a single data point. This is the maximum number of points that can be put into a single bin. The Max Diff field affects whether or not the number of points used matches this setting. 94 Max Diff. Enter the maximum interval, in minutes, between any two consecutive data points that are binned to form a single data point. This setting is used to account for large gaps due to clouds, taking reference images for reductions, etc. where binning points well removed from each other in the curve would adversely affect the average value. If the setting is 0 and Binning is greater than 1, all data points are binned regardless of the interval. A good starting point is approximately double the average time between images during the run. No data point is used in more than one bin, so this is not a running average. If Point X is more than Max Diff minutes from Point X-1, then Point X-1 is the last value in the bin and Point X becomes the first point in a new bin. Search Type There are three types of search available. This radio group allows you to select one and, if necessary, Canopus automatically adjusts the values from the Orders, Min., Size, and Steps fields as needed before being passed to the search engine. Period (reg) This search uses the values in the Orders, Min, Size, and Steps fields "as-is". The search starts with the Min. period and analyzes the RMS error for Steps number of periods, each period being Size larger than the previous period. Orders The orders search determines the setting for the Orders field that provides the smallest RMS value when the period is assumed to be a fixed value (the one found when searching a range of periods with a fixed number of orders). The range of the orders examined is Orders to Orders + Steps, up to a maximum of 15. The Size setting is ignored and internally set to 1. Period (auto) This search differs from the "reg" search in that the increment in the search period is no longer the fixed value in the Size field but becomes geometric, i.e., the increment gets larger with each iteration. The period search range is “Min” to “Min” + (Steps-1) * Size. The actual number of steps is determined by the initial period and the total span (in days) of the data set being analyzed. For a more detailed discussion of the search types, see “A Detailed Look at the Fourier Analysis Routine” on page 99. Raw Check this box to plot the differential magnitudes versus Julian Date. Uncheck the box to plot the differential magnitudes versus phase, i.e., the values are converted to a value between 0% and 100% of the period found by Canopus. If this is the first run at the period search and you haven’t matched the DeltaComp values so that the data is approximately aligned, check this box. Fourier Check this box to display the Fourier analysis results as a theoretical curve superimposed on the data. Sometimes plotting the Fourier solution produces a curve that extends way above or below the data and so you don’t see the lightcurve very well (it’s a flat line). This is usually when the analysis is “filling in gaps” in the data in order to make things fit to the given period. If this happens, do not plot the Fourier curve (uncheck the box) until you have sufficient coverage of the lightcurve and/or a reasonable solution for the period. 95 R Mag Check this box to convert the magnitudes to unity distance, i.e., by applying -5 * log(rR) where “r” is the earth distance and R is the sun distance, to each observation’s value. This puts all data on a constant zero point independent of a given session. If the box is not checked, then the “reference distances” are the earth and sun distances for the first session in the set, meaning that all data are corrected for changing distance by applying the difference between the unity correction value for the first session and that of a subsequent session. So, for the first session, the correction is 0.0. Transforms The checkbox determines if color index and second order extinction corrections are applied to the observations as they are added to the period analysis engine. Not Checked The data are not corrected for color differences Checked The data are corrected using the color index values for the comparisons and target in the current session along with the transforms and second order extinction values in the current PhotoRed transforms set. If you are applying transforms on-the-fly, it is very important that the color index values in the sessions form are the same type, e.g., B-V or V-R, that you used when finding the transforms for your system. For example, if you used V-R magnitudes of the standard stars in a reference field, then the color index values for the comp stars and target must be V-R. Find Click this button to begin the period search. Note that the find button has a down arrow button attached to it. If you click this button, a pop-up menu appears. Find Period This is the default action if you click the find button itself and initiates a single period search. Dual period search This displays the dual period search form that allows you to search for the period of the primary in binary system as well as the orbital period of the satellite. This function should be used only when you have good reason to suspect a binary. Dual period searching requires a thorough understanding of the single period search process. Become familiar with the process on “simple” targets before jumping off the deep end. The Users Guide contains a tutorial on the dual period search feature. You can find the Guide in the \MPO\DOCS directory. Analyzing the Fourier Analysis 96 The Results form appears each time you click the Find button. It also appears if you exclude a point by doing a <Ctrl+Click> on that point on the plot and telling Canopus to excluded the point from further calculations. You can leave the form open as you try different search parameters; it does not automatically close when you start a new search. Double-click on the form’s caption bar to “roll it up” so that all that remains is the caption bar. This allows you to keep it open and off to one side as you do work on the period. Double-click the caption bar again to restore the form to its former size. Data Page Period The estimated period, in hours PE The probable error of the period, in hours 3-Sig Error The three sigma error, or 3x the probable error. This is a more conservative estimate and one often quoted. 2% Errro This is the error that shifts the last value in the data set (by Julian Date) by 2%, i.e., the error that would cause a 7° rotation difference over the total span of the observations. This uses the same formula as used in estimating the error of the sidereal period when doing spin axis modeling. Dispersion The RMS dispersion in units of 0.01m Note that the amplitude of the curve is not given. This is because there is no simple approach to finding the amplitude of the full curve. The Fourier analysis gives the amplitudes of the various orders but using those alone can result in an incorrect value because they are affected by bad data points, the relative strength of the various orders, and so on. Each line of output includes the fit harmonic order, the value of period, the RMS dispersion in units of the a priori estimated uncertainty (thus, 1.0 means the fit is exactly as good as you estimated the noise level to be), and two columns of fit uncertainty in units of magnitude. The first of the two columns of fit uncertainty is the formal uncertainty of the fitted curve, that is, the RMS fit dispersion divided by sqrt[(N)(N-K)], where N is the number of data points, and K is the number of solution constants. The second column is the same, except divided by sqrt[(N)(N-K-1)]. The difference between the values in the two columns is a formal measure of significance of changing the solution. Thus if you force the solution off from the minimum value of dispersion by an amount that raises the dispersion in the first column to be equal to the value in the second column at minimum, then I am "one sigma" off of the least squares solution. Save Click the save button to save the Fourier analysis data. This is important if you are planning a dual period search or using the Lightcurve Ephemeris form (see the Utilities chapter). A sample file is shown below. 4 4 4 4 4 4 4 4 5.20000 5.30000 5.40000 5.50000 5.60000 5.70000 5.80000 5.90000 13.51169 15.82018 5.82324 13.46150 14.17880 4.70908 16.31507 3.52633 0.0130016 0.0152230 0.0056034 0.0129533 0.0136436 0.0045313 0.0156992 0.0033932 0.0130673 0.0152999 0.0056317 0.0130188 0.0137125 0.0045542 0.0157785 0.0034104 Fourier Analysis Values ---------------------------------------Avg: 0.28793 T0: 2451443.500000 97 Order sin cos ------------------------1: 0.01928 -0.02076 2: 0.10653 -0.18914 3: -0.01507 -0.00099 4: -0.03733 0.02526 Dual Period Search Format ----------------------Per: 0.245416667 T0: 2451443.500000 Avg: 0.28793 0.01928 -0.02076 0.10653 -0.18914 -0.01507 -0.00099 -0.03733 0.02526 Do not modify this file! Canopus expects the data to be in an exact format so that it can be used with the Dual Period Search feature and Lightcurve Ephemeris utility. Plot Page This page shows the RMS values versus period. Often you can see the dispersion values rise and fall in a somewhat cyclical manner. This is not always the case. However, you can use this plot to help find alternate solutions by examining periods where the curve is at a minimum. This comes in handy when “aliasing” becomes an issue. Aliasing is when two or more periods have integral or half-multiples equal to the overall span of data. For example, say you observe at 24 hour intervals and catch only the peak of a lightcurve. Is the period 3 hours (8 revolutions), 4 hours (6 revolutions), or 6 hours (4 revolutions)? It could even be something else, 5.333h or 4.5 revolutions. Another example would be that there is a long time between observation runs. You can’t be certain of the number of revolutions between runs without additional data that is obtained close to one of those two runs. If the plot shows several minimums, any one of them is a potential “right” solution and, unless the available data dictates otherwise, should be considered. See “A Detailed Look at the Fourier Analysis Routine” below for a more detailed discussion of this form The Period vs. RMS values – The Period Spectrum A plot of the RMS values versus the period is called a “period spectrum”, which is often convenient when the fit is ambiguous. 98 Some call this a “power spectrum.” Do not make this mistake. A power spectrum uses different values for the Y-axis. The two types can lead to different interpretations under some circumstances. As before, the two uncertainty columns in the results form, i.e., U1 and U2, can be useful for evaluating the formal quality of competing solutions, but this must be used judiciously. Thus a period solution twice as long as the correct value will generally be formally better, because there is less data overlap, but will be quadruple periodic, which is not very plausible. At some level, experience, judgment and even artistry enter into the fitting procedure if the data quality is marginal or the situation is complex, as in "tumbling" asteroids. A Detailed Look at the Fourier Analysis Routine What follows are parts of his explanatory text for the FALC program written by Alan W. Harris, modified to fit the user interface in Canopus. Particularly important to understand is what the program is doing and the several considerations of which you need to be aware as you go through the process of finding a period. Remember two things: first, nothing beats common sense and, second, computers are tools, not prophets or psychics. Overview This routine performs a Fourier analysis of lightcurve data, in units of astronomical magnitudes. It is possible to do a linear least squares fit for a specified period up to any harmonic order, so the program is used by grid-searching linear solutions in terms of period or harmonic order. The program uses only the time tag in Julian days, the magnitude, and the error bar of the magnitude. If no error bar is given – the default in Canopus – the program inserts 0.01 for the "sigma". A good starting point for the number of harmonic orders is 4, but anything up to 15 (the maximum in Canopus) can be used. The total number of solution parameters is 2 * Harmonic Order. Normally you should keep the number of solution parameters to about one-half the number of data points and less is better. There are several ways to approach a period search. If you have a good idea of the period, you can start with a value that's slightly under that and scan a series of periods. Estimated Period Scan The Estimated Period Scan is the result of you making a best guess for the period and other search parameters in an initial search. The Fourier analysis form displays the results. How can you make the period search more efficient and likely to find the correct period? The best method is the choice of scan intervals to try in period searching. The object is to sample periods often enough that successive solutions will not differ by too much, that is, you won't skip over a minimum in the dispersion function without noticing it. Minima in the lightcurve show up without wasting time oversampling if you choose a period increment such that successive period choices differ by less than about 1/10 of a cycle over the entire data span. Thus, Delta = 0.1 x (P2 / T) where T is the time span of the data. For example, example, if T = 125 hours and P =5.7 hours, Delta = 0.1 x (5.7 x 5.7) / 125 = 0.026 hours If your computer is slow and your data set is large, you can get away with this large of a step size. To be safe, it's best to stay a bit lower. Automatic Period Scan What if you have no idea what the period might be? Another feature of the program allows you to scan a really large range of P efficiently. Since the period step size scales as inverse period squared, it is efficient to increase the step size as the trial period gets longer. If you select the “Period (auto)” search option, this tells Canopus that you will be scanning over a large range of P, so the period step size will be increased proportional to 1/P2 as it goes along. 99 Here are the results using a given set of data when using Order = 6, Min. Per. = 2.0, Step Size = 0.01, Steps = 200, and checking “Period (auto)” for the period search type Note that the interval between periods increases as the period increases. With this search, the period can be well-removed from what was found using the Estimated Period Scan that covered the same range of periods. Always try to look at the phased plot of the data when doing a period search. The period found by Canopus may show a lightcurve with only one or many maximum/minimum pairs per cycle. This is not impossible, especially one pair, but anything with multiple pairs should be carefully reviewed as being the result of finding the wrong period. To repeat once more: computers are not prophets, psychics, nor purveyors of absolute truth. They are tools that are only as good as the person using them. Nothing replaces common sense and good judgment. Danger, Will Robinson! What happens when you use a higher number of harmonic orders and the data do not cover a complete cycle? In this case, the “fit” involves a gap. When you use a higher order, not only is the higher order curve able to pass through the data points better (hence lower RMS residuals), it is also able to “recycle” itself faster from the end point to the start point. Therefore, it's able to accommodate a smaller gap (shorter period) in the data. This has no physical reality; the “best” solution is the one with greatest symmetry. When confronted with a situation such as this (less than one full cycle, but more than half), try solving for the halfperiod, to obtain a “composite” with only one maximum and minimum. In effect, this maximizes the symmetry of the curve, which is the physically desirable assumption. You can plot out that solution to see what results, and then double the period value and re-solve with the period fixed to get some idea of the fit. However, since there is only one string of data and less than a full cycle, the composite really is no more than just the single set of data plotted up. Harmonic Order Scan Another scan that should be performed is in harmonic order. Set Orders = 2, Min = 5.8907 (the best period found form a previous search), Size = 0.01 (it’s ignored in this search), Steps = 15, and select “Orders” for the period search type. 100 Formally, NFIT = 11 is best fit but that’s really too high for the given data. To decide if an additional harmonic is formally significant, you can use the two columns of fit uncertainties again, but this time keep in mind that each harmonic order introduces TWO new solution parameters. Therefore, the fit uncertainty has to improve by twice the difference in the two columns to be significant. Note that the probable and 3-sigma errors are not computed when doing this type of search since you are not searching a range of periods. The 2% error is a simple function of the chosen period and so is computed. Be careful about blindly accepting that a given order is the best. Should the dispersion (RMS) fall under 1.0, saying that it is better than the formal noise in the data, you should be at least a little skeptical about the result. Refining the Search Again One last refinement is to do a fine step scan with the Order = 10 so you can home in on the period. Both result sets above used the same search parameters save the harmonic order. On the left is the original order of 4. On the right, the order is 10. Note that the period changed by about 0.0004h (1.4s) going from order 4 to order 10. This is not very significant (though the RMS being cut in half is more so). In other cases, changing the order could dramatically alter the results. 101 A Final Look Save Click the Save button on this tab to save the results displayed on this page. Then scroll down as needed so that you can see the Fourier analysis values. Fourier Analysis Values Avg This is the average value of the lightcurve. If the data are absolute, i.e., on a standard system, the average values can be used in conjunction with the phase angle to fiind the H (absolute magnitude) and G (phase slope parameter) for the asteroid. TO This is the Julian Date for 0° phase angle for the coefficients. This is not the same as the earliest JD value for the lightcurve data and will generally not agree with the zero-point JD shown in the lightcurve plot. Instead, T0 is a value that is about the middle of the data set. Order/Sin/Cos The remaining lines give the order and corresponding sine and cosine multipliers when substituting in the Fourier analysis formula to generate the plot. n – 2l t t0 Bl cos 2l t t0 V ( , t ) V ( ) Al sin P P l 1 See the article by Harris and Lupishko, "Photometric Lightcurve Observations and Techniques" in Asteroids II, pp. 39-53, for a more detailed discussion. 102 Period Determination - The Comp Adjust Form The Comp Adjust form allows you change the DeltaComp value for a session without having to edit the session in the Sessions form. Without the Comp Adjust form, you’d have to open the Sessions form, edit a session, change the DeltaComp value, save the session, close the Sessions form, and find the period again. The Comp Adjust form avoids all these steps. By changing the DeltaComp value for a given session, you move it up or down in relation to the other sessions on the plot. By doing this, you can get the data for a given session to line up with the data from other sessions. Matching sessions is critical to finding the right period since the Fourier analysis routine can find a different period for different session alignments. In many cases, it's easy to use this form to adjust sessions so that they mesh well together. However, there are other times when this is not very easy and where having the data on at least an internal system if not absolute standard makes merging sessions less arbitrary and more exact. The Users Guide “Photometry” chapter contains a tutorial that covers the use of the Comp Adjust form in detail. The Delta Comp Spinner As shown above, when you click on the up or down arrow of the spinner control, the value in the DeltaComp field changes. The default is 0.01m per click. However, if you need to change the value more quickly or slowly, you can do so. No Key Value changes by 0.01m with each click on the spinner. Shift+Click Value changes by 0.1m with each click of the spinner. Ctrl+Click Value changes by 0.001m with each click of the spinner. Replot Click this button after you have changed the value for a given session to have Canopus recompute the period using the shift in the session data. You must replot after changing the value for each session. The reason Canopus re-computes the period is that the Fourier analysis routine can find a different period because of the different way the data from various sessions fit together after changing the “zero-point” of one of the sessions. Shifting Several Sessions at Once You can select more than one session at a time. However, if you select more than one session, the spinner, “DeltaComp” field, and Replot button are disabled. Instead, right-click over the list and select one of three default values to move all selected sessions either up or down: 0.01, 0.05, or 0.1 mag. You can also select a custom offset. If you do, a small form appears where you enter the amount to shift all sessions. 103 Restoring DeltaComp Values As long as you keep the form open, you can restore the Delta Comp values to the ones they had when the form was last opened. Right click on the list to display a popup menu that lets you restore the original value of the highlighted session or all sessions. This is a handy feature if you are trying to manipulate sessions up or down to get a better fit and then decide to “go back to square one” or accidentally change the DeltaComp for a session that you did not intend to change. Period Determination - Manipulating Phased Data Floating and Fixed Range The preferred practice in publishing asteroid lightcurves is to have the vertical scale at 0.6 to 0.8 magnitude range be about as high as the phase between 0 and 100 (or 1.0) is wide. The default in Canopus is forces the vertical range to 0.6 magnitude. The reason for keeping such a scale is to avoid having small changes in the lightcurve appear to be much larger than they are in proportion to the overall curve. For example, one can get the false impression that the asteroid is more elongated than it really is. Of course, if the amplitude is very small, forcing the range may make the curve essentially flat and so all detail is lost. Then it is OK to expand the vertical scale to see the details, but the expansion should be kept to a minimum. Floating Range Check this radio button to have Canopus scale the vertical axis such that the curve is about 70-80% of the plot area height, but with no less than ~0.12 mag total height. Fixed Range Check this radio button and enter the vertical range of the plot. If the amplitude of the curve exceeds the range, Canopus automatically switches internally to use the floating range option but the setting does not change on the tool bar. Click the “Replot” button, immediately to the right of the period slider bar, to replot the data if you make any changes to the range settings. Changing the Period Dynamically After you find the period and plot a phased curve (where the data are folded to fit between 0.0 and 1.0 of the period), you can see the effects of changing the period solution without having to click the “Find” button again. Move the slider bar left or right of center. As you do, you’ll see the new period value and the amount of change in the labels below the slider. Click the “Replot” button to see the effects of the change. This is a handy tool for getting an estimate of the true period error. The one reported by Canopus is the formal error, which should often be increased to provide a more reasonable error estimate. If you change the period by 0.01 h and the plot “falls apart” or the data noticeably no longer line up, then you can put an upper limit on the period error at 0.01 h. Changing the Range of the Period Slider By default, the period slider range is ±0.1 h. If you’re working a long period asteroid, this too little and if you’re working one where you’d like to test very small changes, it is too much. 104 Click on the slider’s “thumb” (button) and press one of the number keys on the main keyboard (not the number pad). This resets the slider to the middle and changes the total range. Key 1 2 3 4 5 6 7 8 9 0 Range (hours) ±5.000 ±1.000 ±0.500 ±0.200 ±0.100 ±0.067 ±0.050 ±0.033 ±0.025 Reset to default (±0.100) Clicking the “Find” button resets the slider range and position to its defaults. Period Determination – Changing Plotting Options The speed button with the “book” icon opens a popup menu with several options. Zoom Chart This menu item displays a form that allows you to change the X and Y scales of the plot independently or in step, e.g., set both to 50%. When the form is closed, the plot is retuned to 100% scaling on both axes. You can save the rescaled plot before closing the form. Show Legend This is a “toggled” menu item. If it is checked, the plot legend showing which symbol represents which session is displayed to the right of the plot area. Show Header/footer This is a “toggled” menu item. If it is checked, the header and footer (title and JD/period information) are included in the plot. Select the menu item to toggle the checked state of the menu. Flip Y-axis This is a “toggled” menu item. If it is checked, the Y-axis is flipped. This is sometimes necessary after importing data from another program so that the plot has the correct orientation where the top represents when the target was brightest. Show Errors This is a “toggled” menu item. If it is checked, the error bars for each data point are included in the plot. Symbol Size This menu item has a radio button submenu to set the size of the plot symbols. The default is 5 pixels. Larger symbols may be useful for generating plots for publication (the default is the one that should be used for plots in the Minor Planet Bulletin). Save LC Plot Select this menu to display a file save dialog. The default format is PNG but BMP can also be selected. The plot is saved “as-is”, what you see on the screen is what’s saved. The size of the plot is determined by the Configuration | Photometry tab settings. Period Determination - Editing Data Using the Plot In some cases you’ll have some “bad data points”, possibly because there was a faint star or some other reason, and you’ll want to remove them from the lightcurve plot and period solution. You can edit the data points in the Session 105 form’s Observation page, but that is a tedious process since it’s more trial and error to guess which data point is bad, marked it unused, and then re-compute the period and re-plot the data. To make things easier, Canopus allows you to edit data points using the plot. In the end, the result is to mark the data point as unused just as if you had done so in the Sessions form. To View Data Point Information Place the mouse cursor over a data point and click the left mouse button. Information about the data point appears in the upper status bar at the bottom of the Photometry page. The date and time are the same as in the image header. The JD is the corrected Julian Date. In this case, the (HJD) indicates the correction is for Heliocentric JD instead of Earth-asteroid light-time. To Remove a Data Point from the Solution Place the mouse cursor over the data point and Ctrl+Click the left mouse button. This displays a confirmation message. Yes Click this button to delete the data point from the solution (but not from the observations table). If you select this option, the Sessions Selection form appears. Unless you want to change which sessions are included in the solution, click OK on the Sessions Selection form and Canopus re-computes the period less the data point and re-plots the solution. NO Click this button to keep the data point in the solution. If you remove a data point and it still displays, you probably have duplicate entries in the observations file. See “Duplicate Data” on pg. 81. Saving Plots All plots can be saved using a menu option or button provided for that purpose. The default is to save as a PNG since these are much smaller than BMP files and have very little compression loss. When a file dialog appears, select type of file before saving. Regardless of the extension you give the file, MPO software forces the extension to the selected file type. Pan and Zoom Many of the plots presented in Canopus and PhotoRed allow zooming in to see a portion of the plot in detail and then, while still zoomed in, to pan around the entire plot to look at other regions up-close. 106 Here is a screen shot of Canopus after generating the lightcurve of an asteroid. The box has been added to indicate the approximate region on which we want to zoom. Zooming In Move the mouse cursor a little above and to the left of the region that you want to see closer up. Drag the mouse cursor a little below and to the right of the region and then release the mouse button. Now you see the region filling the entire plot area. You can zoom in as much as you want. If you want to zoom in some more, just repeat the process of selecting a region but on the zoomed plot. It is not necessary to reset the plot to zoon in more. Zooming Out To zoom back to normal view, reverse the process, i.e., place the mouse cursor anywhere on the plot area, drag up and to the left a few pixels, and release the mouse. The plot returns to normal scaling. Panning “Panning” means to move the entire set of data in any direction. You can pan the plot regardless of the zoom level. Move the cursor anywhere on the plot and drag using the right mouse button instead of the left. 107 This screen shot show the original plot after panning to the right (which moves the data to the left. The more common use of panning it to move about the data set after zooming in. Reset Panning Use the same procedure to reset the plot as you did for zooming out, i.e., drag up and to the left from anywhere on the plot and then release the left mouse button. Period Determination - Viewing the Lightcurve Data If you have “AutoSave raw data” checked on the Photometry tab of the configuration form (see page 40), then each time you use the Find button to find the period of the lightcurve, Canopus saves the session and observation data to one or more text files based on the sub-selections you made The data are saved in \MPO\CANOPUS directory under the names <NAME>.TXT Full header information for each session plus the complete data for each observation. Somewhat different format from using the “To File” option on the Sessions form. <NAME>_PHASED.TXT Full header information for each session plus the data ordered in ascending phase (from 0.0 to 0.99). The observation data includes only the phase, normalized flux, JD, and magnitude corresponding to the normalized flux. <NAME>.NRM A Binary Maker compatible file for importing data into that program. There are only two colums per observation: phase and flux. See notes below. <NAME>_X-Y_R_CONDENSED_LTC.TXT Full header information for each session. The observation data consists of J.D., magnitude, error (in mag), and session number from which the data was taken. The JD are corrected for light-time travel. <NAME>_X-Y-R_CONDENSED_NoLTC.TXT Same as CONDENSED_LTC except that the JD are not corrected for light-time travel. Where <NAME> is the name in the Object field for the session. Any spaces in the Object name are replaced by underlines. X-Y represents the first and last session number of the selected sessions. If only one session is chosen, then only X is given. R is either “REDUCED” or “NOTREDUCED” to indicate if the magnitudes are reduced to unity distance or not reduced. These extra indicators are designed to help those using MPO LCInvert for asteroid modeling to quickly identify the type of data and to generate multiple CONDENSED files with only one session without having to rename the file after each period search, which generates the CONDENSED file. 108 Note that the magnitudes generated for all but the plain text file option include adjustment for phase, distance, and Delta Comp. Version 2 of Binary Maker allows only 215 data points. If your data set includes more than this number of observations, you’ll need to edit the NRM file by removing random lines until there are no more than 215 lines. Version 3 allows for a larger number of data points. Also, version 2 expects old DOS 8.3 file names, e.g., VARIABLE.NRM is OK but V432_PER_20071024.NRM is not. You will need to rename the file, if necessary, to conform to that file name format. Period Determination - Normalized Plots The options on the Configuration | Photometry page allow plotting of the normalized data, an example of which is shown above. The plot is always black dots on white. The size of the plot when saved to a file is controlled by the Configuration - Photometry page settings. To fit the requirements for Binary Maker, normalized data is where the magnitudes have been converted to flux and the maximum value is 1.00. Furthermore, the deepest minimum is set to 0.0 phase and the maximum occurs at either 0.25 or 0.75. Because of these requirements, the shape and phase alignment of the normalized curve may not match that of the lightcurve plot on the Photometry page of the Canopus main form. To access the Normalized plot, press Ctrl+5, click the Normalized plot speed button on the main toolbar, or select Pages | Normalized from the main menu. Altering Normalized Phase Data If using Binary Maker to construct a binary star system based on observations in Canopus, the fit of the actual data vs. the synthesized data sometimes differs only by a matter of “sliding” the synthesized data left or right. This is actually accomplished by changing the phase angle for each data point in the actual data and can be done only within Canopus. Assuming you have “AutoSave raw data” checked in the configuration settings, then whenever you do a period search, Canopus re-computes the phase angle for each data point based on either the earliest date in the data set or the corrected J.D. of the maximum or minimum of the curve. Which J.D. is used is determined by the settings of the Photometry page of the Configuration form. If obvious initially or after importing into Binary Maker 3 you see that the Canopus data needs to be shifted en masse left or right or up/down, you can do so on the Normalized plots page. Shifting the Phase 109 Use the slider bar or enter a number from -0.50 to +0.50 in the entry field and then click the Replot button to the right side of the toolbar. The data replotted with the phase shift included. Shifting the Normalized Zero Point If the data are too high or too low despite all modeling efforts in Binary Maker, you can shift them up or down by using the scroll bar or entering a value from -0.10 to +0.10 in the entry field. Click the Replot button on the right side of the toolbar to display the shifted data. You must click the Replot button on the Normalized Plots page to generate new data after changing the Phase and/or Zero Point. Saving New Phase Data Click the Save Shifts button to save the adjusted data after first clicking the Replot button. Click the Save Plot button to save the new plot after first clicking the Replot button. Period Determination - Finding the Time of Extreme Amplitude (TOM) Variable star observers working with eclipsing binaries use the time of minimum (usually the primary minimum) as a reference point. Other stars, e.g., RR Lyrae, are referenced by times of maximum. By comparing the measured time of minimum or maximum (TOM, i.e., the time of extreme amplitude) for a given set of data to the predicted time based on a known period and initial time of extreme amplitude, it’s possible to determine the period of the object and whether or not the period might be changing. Canopus uses the Hertzsprung method as detailed by Henden and Kaitchuck in their book to find the time of extreme amplitude and generate an ephemeris that shows the times of extreme amplitude in the past and future. Use the period search routines in Canopus to find the period of the data before beginning unless you already have an assumed period. In which case, you still need to plot the observation data. The initial calculations to find the time of extreme amplitude are based on days, regardless of the configuration settings. The TOM (Time of Minimum/Maximum) Calculator can work in either hours or days once you’ve found the TOM. When working with the TOM calculator, you must use data from one and only one session. If you include data from more than one session, the results are unpredictable. Changing Captions The button that invokes the TOM calculator, located at the bottom right of the Photometry page, changes its caption depending on the Configuration | Photometry tab settings. If the configuration is set to plot 0% at minimum, then the caption on the button and on the calculator will include “Minimum”. If 0% is at maximum, then the two include “Maximum.” If the Configuration settings are such that 0% is not forced to be at maximum or minimum, then “Maximum” is assumed and used. Calculating TOM After you have plotted your phased data, click the “Compute Time of Minimum (Maximum)” button at the bottom right of the Photometry page. This displays the TOM search form. 110 Step Size Enter the size of the steps (in days) on either side of minimum from which to use or interpolate a magnitude value. Steps Enter the number of steps on either side of minimum to be used. The minimum is three. Additional steps can improve the accuracy of the results but using too many eventually has diminishing returns and increases the time of calculation. Mid-point JD Enter the Julian Date of the assumed time of minimum/maximum. Canopus automatically enters value for you using the JD of the faintest data point. There must be sufficient data on either side of the minimum for the TOM Calculator to work. To assure a proper calculation, there must be two points in the observation data where JD (Mid – Steps * StepSize) and JD (Mid + Steps * StepSize). OK Click the OK button to start the TOM calculations. Period Determination - TOM Calculator The TOM (Time of Minimum/Maximum) Calculator shows the results of the TOM search and allows you to find previous and future times of minimum. 111 Use Computed Date Check this box to use the JD value that is in the “Computed” field. Uncheck the box to use a random date. This enables the “Near” field and allows you to select a date from a pop-up calendar. Computed This is the computed TOM based on the search just performed. The Universal Date and Time equivalent are shown to the right. You can change this value but the UT values are not updated to reflect the change. Near Enter a date in the Windows date format (with all four digits of the year) or click the speed button next to the field to chose a date from a popup calendar. This field is enabled only if “Use Computed Date” is not checked. Period This is the period of the lightcurve. The units (days or hours) are determined by the configuration settings. Canopus automatically inserts the most recent value from the period search. Hours Check this box if the period is in hours. Uncheck the box if the period is in days. When the TOM Calculator first appears, the box is set according to the configuration settings. Steps Enter the number of times of minimum to find. If you select “Both”, the actual number of TOM values is 2*Steps + 1. Ahead / Back / Both Check the Ahead button to compute TOM values later than the JD Min. Check the Back button to compute TOM values earlier than the JD Min. Check Both to compute TOM values before and after the JD Min value. Compute Click this button to compute the TOM ephemeris. The list box displays the results of the calculations. 112 Exchanging Canopus Photometry Data One of the main benefits of Canopus is that it can easily export and import data from other observers or machines on your network to make a combined data set for period analysis. When Canopus is being used at both ends of a collaboration, the exchange is particularly easy. The process is still relatively easy if Canopus is not being used. It can export the photometry data to a simple text file that can be read by another program or import text files created by other programs. The import utility allows considerable flexibility with respect to the format of the data in a text file to be imported, with only a small set of absolute requirements. Export Sets The term export set is used freely throughout the Canopus documentation. The term Canopus export files or Saved Sessions is also used and means the same thing. An export set consists of two files, one containing one or more sessions and the other containing all observations for all sessions in the sessions file. When Canopus is used at both ends of a collaboration, these files are the preferred method of exchanging data. The export set can also be used as a means of archiving photometry data. Once the files are created, you can remove the sessions from the main PHSESS/PHOBS files in order to keep those files reasonably sized. If you do this, make sure you keep a copy of the CANOPUS.EXE file that created the files, just in case a future version has trouble reading them. Every attempt is made to assure that Canopus is backwards compatible but there is always a chance for error. One of the great advantages of using export sets is that there is no doubt about how to deal with light-time or Heliocentric JD corrections. The raw data in the observations files is not corrected. The settings in the sessions data provide the necessary information to apply the appropriate correction in the correct manner (assuming the session data was properly entered). This is not the case when importing text files, where the sender must make it clear whether or not corrections have been applied. Working with Export Sets There are several critical steps to follow and ideas to keep in mind if you are exchanging export set files to merge into a common data set. These apply even if you’re not collaborating with others but working with multiple export sets of your own all involving the same target – in effect, collaborating with yourself. The Users Guide includes an entire chapter covering the basics of Importing and Export data in Canopus. The following sections do not contain step-by-step instructions but do include additional information and details on specific data requirements. Overall Procedure 1. Make backups of the original file pairs before doing any merging! 2. In general, do not use the primary sessions and observations files (PHSESS/PHOBS) for merging. The exception to this rule would be if you measured images on another machine and want to import the data into these primary data files on the machine where you usually work. 3. If you have observations of your own to be merged with other data, export the sessions for the target from your primary files to an export set. Then load these (“Photometry | Load export set”) and make them the master set for the collaboration. If you do not have observations, pick the files from one of the observers in the group and make it the master. 4. Each time you want to add additional observations, use the “Photometry | Load export set” menu option to load the master data set. Then select “Photometry | Import into export set | from file” on the main menu. Locate the session file to be imported in the file open dialog, and click OK. This imports the data from the session into the master data set. 5. If you're using a master set that does not include data from your primary files and want to incorporate your data into that master set, then 113 a. Load the master data set. b. Select “Photometry | Import into export set | from PHSESS” from the main menu. This imports your observations into the master data set. Repeat this process each time you get a new set of observations. See “Importing Export Set Files” (pg 115) for more information. When new data sets are merged into the master set, all session numbers, including those in the master data set, are changed so that there are no sessions with duplicate session numbers. If there are two or more sessions with the same date (the result of merging observations from several observers), the session in the master data set takes precedence and is the lowest numbered. Should the master set get out of numerical and/or date order, which can happen if you get a set of observations that are in the middle of those already in the master set, Canopus provides a utility that can renumber and sort the sessions so that they are again in numerical order based on ascending date order. There is also a utility to make backups of the master set without having to use the export to export set files. Important Rules to Follow 1. Never import a file more than once. 2. Never switch the roles of files, i.e. do not start merging using one set as the master and then at another time, load a different set as the master and merge what was the master data set. You will get duplicated observations under different session numbers! 3. Why can’t duplicates be eliminated? When importing, the program has no idea if the session is from the same or a different observer. The dates alone won’t suffice as a “tie-breaker” since two or more observers may have observed on the same date. The “Object” field is identical as a requirement. The instrumentation can’t be guaranteed to be different, and so on. 4. Everyone must always use the same name (including spaces or other characters between words) in the “Object” field on the Sessions form. The process is not case-sensitive but it would be easier if everyone followed the same capitalization rules, too. 5. The session file name must end with “_SESS.FF2” (single underscore and without the quotes) and the associated observations file name must end with “_OBS.FF2” (single underscore and without the quotes). What precedes those endings must be exactly the same for both files. 6. If sending export set files to another user periodically during a campaign, include only new sessions/observations, i.e., do not include sessions/data that you may have sent in a previous export set. Otherwise, Canopus will import those earlier sessions again and you'll have duplicate data. For example, say you created a export set with sessions on October 1, 2, and 3 and sent hose to the person merging data sets. You then observe on October 5 and 6 and want to export sessions again. During the export to export set, do not select the sessions from October 1, 2, or 3; select only those for October 5 and 6. 114 Exporting Data The Users Guide has several tutorials that cover exporting to export sets or text files, including the ALCDEF standard. Please refer to that Guide for details on exporting data. Importing Export Sets Importing one or more export sets into Canopus is a straightforward process. Where any complications come into play is when you are the principal in a collaboration and receiving data files in one form or another on a specific target. Some general guidelines are covered in “Working with Export Sets” above. This section will deal primarily with the mechanics of importing data from export sets. It is always a good idea to make a backup of the sessions/observations files into which you'll be importing data before you try the import. It's very important to remember that when you are working with Saved Sessions file, i.e., you have loaded a master saved sessions file set, that you are working with a temporary copy. Any changes you make will be lost until and unless you use the backup utility. See Photometry Data Management on page 121 for more information. The process of saving and merging lightcurve sessions may seem a bit daunting at first. However, with a little care you’ll soon master it. This feature has been put to highly successful use by teams of up to a half dozen observers and more to help determine the parameters of some very tricky lightcurves. If you’re looking for help, in addition to technical support, use the MPO User’s Group on the MPO web site to get advice from “real world” users. http://groups.yahoo.com/group/MPOSoftware/ Since the Users Guide covers importing of export sets in sufficient detail and there is no additional information required, refer to the Users Guide for importing data in Canopus when the source is one or more export sets. Importing Data from Other Programs Canopus is able to import data from other programs as long as the program being used can export the data to a simple text file that meets some minimum requirements. Before importing data, you should be familiar with some rules for the import files and rules for the import data fields. The Users Guide has a brief tutorial showing one of many possibilities for importing data from other programs. That tutorial covers the essential principles and steps. The following explains some of the data rules and data field definitions. Conversion Defaults For Canopus to work, each observation must have an entry for the target and at least one comparison star as well as the date/time of the observation. However, some programs provide only the date/time of the observation and the computed differential magnitude. In this case, Canopus forces the Comp1 values to 0.000, so that when the program computes the differential magnitude, i.e., Target–Comparison, the net result is the differential value provided in the import file. The import setup allows for the possibility that the differential magnitude was computed in the opposite sense (Comparison–Target). General Steps for Importing Data 1. Make a backup of the current sessions/observations files. 2. In the Sessions form, create a new session. 3. Fill in the information for the scope, camera, temperature, date, object, etc. 115 4. Save the session. Note that the Import button is disabled when creating a new session. 5. Canopus does not allow importing the data while creating a new session, as this could lead to erroneous ties to existing data. 6. Make sure the just created session is highlighted in the sessions table and then click the Edit button to edit the new session. 7. Click the Import button. This displays the Observations Import form. 8. If the session already has observations, you’ll see a warning message asking if you want to continue. Unless the data to be imported truly belongs to the session and is not already part of the data, you should abort the import process so that you don’t double up data. Once you have imported the data using the Observations Import form, click Save on the Sessions form to save the edited session. If you're working with a master export set, you must use the backup utility or export the sessions to a new Saved Sessions set. Otherwise, the imported data is not permanently saved in the master. This step is not required when using the primary PHSESS/PHOBS files. Rules for Import Text Files The file should contain one and only line per observation. No other data, e.g., header lines, blank lines, etc., should be in the file. The fields must be delimited by one of the following characters, Comma Spaces Tab Semicolon (ASCII (ASCII (ASCII (ASCII 44) 32) 9) 59) Alternately, the columns can be of fixed width using spaces to pad the column to the specified width. All columns must have the same width. The method for delimiting fields must be consistent throughout the file. For example, it cannot use a mix of commas and spaces to delimit fields. The double quote character (ASCII 34) can be used to surround each field. There must be a matching closing double quote for each opening double quote. For example: valid entry invalid entry invalid entry “9.546”,”14.221” “9.546,”14.221 “9.546”,14.221 1. The minimum data required is a Julian Date and differential magnitude. Two fields, the Universal Date and Universal Time of mid-observation, can be used in lieu of the Julian Date. See “Rules for Import Fields” below. 2. Whenever the data is a floating-point number, the decimal character in the file must match the decimal separator in your Windows settings. Do not include thousands separators. 3. Floating point numbers must include a leading zero if the absolute value is less than 1. For example: 0.934 or –0.321. 4. While the fields can be in any order, they must be in the same order for each observation. Rules for Import Fields As mentioned earlier, the minimum data required for each observation is a Julian Date (or Universal Date/Time pair) and differential magnitude. However, this does not provide a very complete record of how the results were obtained. Canopus exports 17 data fields and two derived fields to text files, which allows one to determine just how the differential magnitude was computed and to check the stability of the comparisons. 116 Following is a description of those 17 fields and the rules for each when the data is included in a text file to be imported into Canopus. 1. Julian Date This is the Julian Date for the mid-time of the observation. For example: 2449600.2456. The import process allows you to specify this or a different offset. The JD can be corrected or uncorrected if the object is an asteroid since the settings for the EDist and SDist fields on the Sessions form can be made to account for either. The JD must be uncorrected if the object is a variable star and heliocentric JD corrections are needed during period analysis. This is because the entry fields in the Sessions form cannot be set so as to force a 0 correction for all dates. If this field is not in the file, then the file must include the Universal Date and Universal Time as separate fields for each observation. 2. Universal Date This is the Universal Date for the mid-point of the observation. See the discussion under "Julian Date" regarding corrected versus uncorrected dates. The entry must be in yyyy/mm/dd format, using leading zeros as required. For example: 2002/02/10 for 2002 February 10. If this field is not in the file, then the file must contain the Julian Date for each observation. 3. Universal Time This is the Universal Time for the mid-point of the observation. See the discussion under "Julian Date" regarding corrected versus uncorrected dates. The entry must be in hh:mm:ss 24-hour format, using leading zeros as required. For example: 13:05:09. If this field is not in the file, then the file must contain the Julian Date for each observation. 4. Air Mass Enter the air mass for the object at the time of the observation. For example: 1.023. If this field is not part of the imported data, then after importing the data, you should use the feature on the Sessions form of Canopus that computes the air mass for each observation so that extinction corrections can be applied. 5. ObjectMag The value is the “absolute” magnitude of the object, not the instrumental. For example: 13.219 If this field is empty, contains an invalid entry, or is not included, Canopus assigns 99.99. 6. If you have selected derived magnitudes on the Configuration - Photometry page and the import file has only JD/magnitude pairs, select this field on the Observations Import form. Do this even if the values are not absolute values but differential. Otherwise the program will not find data in this field when it tries to do period analysis and plotting. ObjectInstMag The value is the instrumental magnitude of the object. By definition, this must be a negative number. For example: –8.544. If this field is empty, contains an invalid entry, or is not included, Canopus assigns 99.99. While this is a positive number, 99.99 is a “constant” used by Canopus to indicate “no data”. If you have selected instrumental magnitudes on the Configuration - Photometry page and the import file has only JD/magnitude pairs, select this field on the Observations Import form. Do this even if the 117 values are not negative (as instrumental magnitudes tend to be). Otherwise the the program will not find data in this field when it tries to do period analysis and plotting. 7. ObjError This is the total error in the measurement of the target. Therefore, it should include not only the error in the target but the combined error in the comparison star measurements. Tied with this is the "Error is SNR" check box. If the error is in magnitudes, this box should not be checked. If the error is the SNR, then check the box. In the latter case, the SNR is converted to a magnitude using 1.0857/SNR. 8. Comp1Mag The value is the “absolute” magnitude of the first comparison star, not the instrumental. For example: 13.219. If this field is empty, contains an invalid entry, or is not included, Canopus assigns 99.99. 9. Comp1InstMag The value is the instrumental magnitude of the first comparison star. By definition, this must be a negative number. For example: –8.544. If this field is empty, contains an invalid entry, or is not included, Canopus assigns 99.99. While this is a positive number, 99.99 is a “constant” used by Canopus to indicate “no data”. 10. Comps 2 through 5 (Fields 10hrough 17 This requires eight additional fields. If this field is empty, contains an invalid entry, or is not included, Canopus assigns 99.99. 11. Use (Field 18 The value indicates if the observation is to be used in the differential calculations. Use ‘1’, ‘T’, ‘Y’ (upper or lower case and without the quotes) if the observation is to be used. If the field is not included but there is a valid entry in field 6 or 7, the value is set to ‘T’. Observations Import Form The above screen shot shows the form after data has been imported from a text file. Importing does not automatically add data to the Canopus database files. Instead, it allows you to review the data before committing it to the database files. Delimiters The Delimiters radio buttons are used to indicate the delimiter character used between fields. Except for the space delimiter, there must be a single delimiter between fields, e.g., if the delimiter is a tab, there can be one and only one 118 tab between fields. Having two or more consecutive delimiters “fools” the import process into thinking there are more fields than are actually in the observation. In the case of the space delimiter, any number of spaces can exist between columns (fields). However, keep in mind that there can be no spaces within a field unless it is enclosed in double quotes. Otherwise, the program will not correctly parse the file. For example, a calendar date of 2005 05 31 is seen as three fields while "2005 05 31" is seen as one field. If you select “Fixed Cols”, you must enter the number of characters per column in the “Width” field. Every column must have the same width. Fields List This is a drag/drop checklist that allows you to set not only which fields are in the import file but the order in which they appear. Selecting a Field To include a field, meaning the data is in the file being imported, click on the field so that the ‘X’ appears in the box next to the field name. To exclude a field that has the ‘X' appearing next to it, click on the field name so that the ‘X’ is removed. To select more than one field, use the standard Windows methods of selecting multiple items in a list. To select a range of items, click on the first item and then Shift+Click on the last item in the range. To add (or remove) an item to those already selected, Ctrl+Click on the item so that the ‘X’ appears or disappears as desired. Changing the Order of the Fields The list defaults to the order of the fields in the User Star table. To change the order, select the item to be moved and then click the Up or Down arrow to change its position in the list. If you hold down the button for about ½-second, it automatically repeats so you don’t have to click the button repeatedly. If you change the order of the fields after you have imported the data, you must click the “Convert” button to have Canopus reload the file and parse it according to the new field order. When you move a field, all selected fields are deselected, except the one that you are moving. It’s best to arrange the fields in the order you want and then select the set of fields to be imported. Base JD Enter the base Julian Date if the imported data includes the Julian Date field and is not the full Julian Date. For example, if the data represents the Julian Date - 2450000.0 (5215.8678 for 2455215.8678), enter 2450000. If the data is the complete Julian Date, e.g., 2455215.8678, enter 0 in the field. This field must be set before you load the import file. Negate Obj. Mag Check this box to have the ObjectMag field value (Field 5 in the previous section) multiplied by –1. The normal sense of computing a differential magnitude is Target – Comparison star (or average of several stars). If importing data that includes only the differential magnitude, i.e., there is no actual comparison star data, it’s possible the differential value was computed in the opposite sense: Comparison – Target. This would lead to “upside-down” data in Canopus. By checking the box, you - in effect - flip the sense of the computation and, graphically, the Y-axis for the given data. 119 Error is SNR Check this box if the data includes an error field, you are importing that field, and the error is the SNR. If the error is in magnitudes, then do not check this box. If the error is SNR, then it is converted to magnitudes using 1.0857/SNR. Only one error is allowed, so it should be the total error in the measurement. It is stored in the ObjSNR field of the PHOBS table, which is not normally displayed except in the import form. The errors for the comps are set to 0 so that the net effect is to make the total error that which was imported. Load Click this button to display a file open dialog. Locate the file to be imported and then click Open on the dialog. The program loads the file and parses it according to the settings in the previously discussed items. Loading a file does not commit the data to the Canopus database files. That must be done from the Data tab. Convert If you change any of the settings after the file has been loaded, click the Convert button to have Canopus parse the original file data according to the new settings. If this does not seem to work correctly, it may be necessary to Load the file again. Reviewing the Data After you Load (or use the Convert button after changing settings), the first tab of the form shows a text representation of the parsed data. The Data tab shows the data as it would appear in the Sessions form had the data been measured directly in Canopus. This allows you to review the data to be sure you’re comfortable with it before it is committed to the Canopus databases. You cannot edit the data on either tab. If the data is wrong and can be fixed by changing the settings, e.g., which fields are imported or the order, make the necessary changes and use the Convert and/or Load buttons. If the data is inherently wrong, you will need to fix it in the import file first. Click the OK button to accept the data and import into the actual Canopus database files. A message at the end of the import tells you how many records were transferred. 120 Photometry Data Management When working with the primary sessions and observations files (PHSESS/PHOBS.FF2), all changes are automatically recorded directly to those files. This is not the case when working with export sets. When you first load an export set, you are working with a temporary copy of the files. Any changes such as adjustments to the DeltaComp value or adding/deleting sessions in the sessions file will not be saved unless you take specific actions to do so. If you do not take these actions, then the next time you load the same export set, all changes will have been lost. Photometry Data Management – Automatic Backups You can have Canopus ask you every time it closes whether or not you want to make backups of the critical user files (see page 10 for which files are copied). To do so, use the Configuration settings on the General tab (see page 27). This feature does NOT backup the temporary files in use should you have an export set loaded. If that is the case, do NOT have Canopus backup files. Instead, cancel the shutdown and use the manual backup described below to assure that any changes made to the temporary files are copied back to the original source files. There are three menu items under the Utilities main menu in Canopus that deal with sessions and/or observations file management. Photometry Data Management - Backup current sessions / observations This function makes a backup of the current (active) session and observations files. The files are saved under the same name as the originals. In the case of export set files, the program remembers the name of the files when they were loaded and uses those names, not the names of the temporary files. Select Utilities | Backup current sessions/observations from the Canopus main menu. This displays a directory selection form. Select the directory to where you want to make the backup copies. If you select the same directory where the original files reside, a warning message appears. It is best that you click Cancel and select a different directory. If you try to overwrite the original files and something goes wrong, you will have neither a good set of files nor a good backup. If you are using the main PHSESS/PHOBS files at the time, i.e., you do not have an export set in use, you should not chose a location under the MPO directory tree. Otherwise, should you uninstall the program, the PHSESS/PHOBS files are removed and you will lose your data should you later decide to reinstall the program. Once backup copies have been made, a confirmation message appears. Photometry Data Management - Pack/renumber current sessions/observations This function makes a backup of the current files and then packs (removes dead space) and renumbers the sessions so that the session numbers or contiguous (no gaps). You also have the option to renumber the sessions in ascending date order. This can be handy when you are using a master export set and importing sessions from different observers that arrive out of date order. Select Utilities | Pack/renumber current sessions/observations from the Canopus main menu. This displays the Pack Photometry Files form. 121 Using this form always packs the files. This removes dead space that may be the result of adding/deleting sessions. Renumber Sessions Check this box to renumber the sessions so that session numbers are in ascending order with no gaps (contiguous). Regardless of the original numbers, the first session after the renumbering is 1. If you check this box, the "Sort by Date" box is enabled. Sort by Date Check this box to renumber sessions and force them to be in ascending date order. The date is determined by the Date and Start Time fields in the sessions file and entered via the Sessions form. Ties go to original order of entry. This box is disabled unless the "Renumber Sessions" box is checked. Click the Process button to start the pack and renumber. Note that if you have a large number of sessions and/or data, that this process can take several minutes. During that time, the form is disabled so that you cannot accidentally close it or start the process again. Furthermore, since the form is modal, you will not be able to do anything with Canopus while the processing is going on. What happens during the processing depends on which fields are currently active. PHSESS/PHOBS Files Canopus makes a backup of the two files in \MPO\COMMON. These files are named PHSESS_YYYYMMDD_HHMM.BAK PHOBS_YYYYMMDD_HHMM.BAK Meaning that the date/time of the backup become part of the file name. Note that the date/time stamp of the file is kept the same as the original file and so that may not agree with the date/time that is part of the file name. These files are not deleted after the pack and renumber. Master Export Set Canopus makes backup of the temporary files being used to hold the original export set data. Once the pack/renumber is completed, a warning message appears. Click OK. 122 Before you go on, use the backup utility to save the packed/renumbered files to their original names. Otherwise the changes are lost. The backup copies of the temporary files are not saved after the pack/renumber. This could result in a number of backups with no easy way to know what data was stored in them. If you use the backup utility as you should, then the changes you've made are saved and there is no need for "blind" backups of the temporary files. In the case of renumbering the PHSESS/PHOBS files, a different confirmation message appears indicating the process is complete. Since changes to PHSESS/PHOBS are automatically saved (no temporary files are involved), then there is no immediate need for doing a backup. Managing Sessions Lists With the ability to open more than one session of Canopus at a time, it was necessary to make several changes on how Canopus keeps track of the last selection during a certain action. Among these is when choosing photometry sessions. Whenever you do that, the sessions were saved to the Windows registry so that if you reopen the Select Sessions form, the previous selection was automatically reset. This is handy when you have ten sessions, not consecutively numbered, and you used only the first, second, third, fifth, seventh, eighth, and tenth sessions the last time you selected sessions. Canopus remembers not only which sessions were selected but the object for which they applied as well. As you do more lightcurve period analysis, this could result in a large number of registry entries (one for each object) with most of them not being used after a period of time. The Manage Sessions Lists utility allows you to delete the entries for objects no longer being studied. Select Utilities | Manage sessions lists from the Canopus main menu. This displays the Sessions List management form. Sessions list box This box contains a list of objects for which a set of selected sessions has been stored. To select an object, check the box next to its name. To deselect the object, click the box again - until the check is removed. This is a typical Windows multi-select box, meaning that Shift+Click and Ctrl+Click selects ranges of or noncontiguous items respectively. Select all Click this button to select all objects. Clear all Click this button to delselect all objects Delete Click this button to delete all selected objects Once you have set the selection you want, click the Delete button. This removes the set of selected sessions for each object and then the object itself from the windows registry entries. 123 124 Database Conversions and Internet Links Asteroid orbits are updated daily, and the files that ship with Canopus will quickly get out of date. The hot links provided take you directly to the page on the appropriate site where you can download the latest data file. The links do not automatically download the file for you. ASTORB - Lowell Observatory Database Here is part of a sample listing when using this hot link: 09/26/09 09/26/09 09/26/09 09/26/09 09/26/09 09/25/09 08:27AM 08:31AM 08:27AM 08:32AM 08:33AM 09:21PM 14,418 74,306,928 28,945,146 33,443 23,508 19,576 090925.add astorb.dat astorb.dat.gz astorb.html astorb.txt astorb_landmarks.html Download one of the files in bold. It is not necessary to do both. If you are doing daily updates download files that have the ADD or DEL extension. These files indicate the date in YYMMDD format, e.g., in the list above, the ADD file is for 2009 September 25. If you download the DAT version, be sure to save it as a TEXT file, not as an HTML page. Also, save it with the same file name. The conversion program expects to find ASTORB.DAT. If you download the GZ file, you must decompress the file using GZIP, WINZIP, or some other product that handles the GZIP format. The decompressed file must be named ASTORB.DAT MPCORB - Minor Planet Center Asteroid Table The Minor Planet Center makes available its MPCORB database of asteroid elements via this site. Here is a sample listing when you use the hot link to reach this site: 09/26/09 09/26/09 09/26/09 09/26/09 09/26/09 09/05/09 09/05/09 09/05/09 02:19AM 02:42AM 02:44AM 02:45AM 02:47AM 05:08PM 02:14PM 02:14PM 61,509 73,433,158 16,298,340 77,473,753 16,301,119 1,043 1,463,296 449,455 DAILY.DAT MPCORB.DAT MPCORB.ZIP MPCORBcr.DAT MPCORBcr.ZIP ReadMe.txt Soft01.DAT Soft01.ZIP Download any of the MPCORB files in bold. As you can see, these files are quite large, so leave yourself enough time. If you have a recent version of MPCORB and want only the latest editions, download DAILY.DAT. Keep in mind that you must download this file daily to keep the MPCORB database in full step. If you miss a few days or more, you should download the MPCORB files and do a complete conversion. The conversion program automatically decompresses the ZIP version of MPCORB, thus saving download time if you get it instead of the DAT file. LONEOS - Lowell Observatory LONEOS Catalog This file contains good to excellent reference stars for photometry. It is used by Canopus to establish the magnitude vs. intensity relationship for measuring magnitudes. Here is part of a sample listing when using this hot link: 09/17/09 09/17/09 09:28PM 09:29PM 1,836,259 514,334 loneos.phot loneos.phot.gz Download one of the two files in bold. If you download the GZ file, it must be decompressed to a text file using GZIP, WINZIP, or any other program that handles the GZIP format. 125 The conversion programs work with the data files downloaded with the hot links described above. User Star The User Star database is a set of stars not necessarily included in other catalogs already mentioned throughout the manual. The conversion routine allows you to enter data manually from any number of on-line sources. It also has an import feature where you can convert photometric sequences developed by Arne Henden. Those sequences can be downloaded from ftp://ftp.aavso.org /public/calib/ The files are simple text files and have the DAT extension. There are quite a few files with more to come. The sequences can be used to help calibrate your photometric system or, at the very least, provide much higher quality M/IR solutions than would be possible using the USNO catalog. User Elements The User Elements form can be used to manage elements manually entered or imported via the MPCORB Import utility. The latter can import from and text files that follow the same format as the MPCORB data file, meaning the Daily Orbit Updates (DOU) or even one-liners from various pages of the MPC site. This can be particularly handy when following objects on the NEOCP and so not in the MPCORB or DOU files. Links to Other Sites If you can connect to the Internet, then you can click on any one of the links listed below and reach the indicated site. If the link is an e-mail address, you must have a properly configured e-mail program available. Changing Hot Links The URL (Universal Resource Locator) addresses used for the links were correct at the time the program was copied to the master CD. Of course, things change and so any given link’s address might change. Too, you may want to change one of the four “My Favorite” links from time to time. To change the URL for any given link, right-click while the mouse cursor is over the link to be changed. This displays a small entry form. Enter the complete and correct revised URL. Canopus does not validate the entry. It is strongly recommended that you not change the settings unless you are certain of what to do and not before you carefully write down the previous entry. For URLs, be sure to include the http:// or ftp://. If you are changing an e-mail address, be sure to include “mailto:”, e.g., mailto:[email protected] 126 ASTORB Conversion This program converts the ASTORB database to a format compatible with the MPO programs. This program modifies ASTORB.FF2. File Use this to find the ASTORB.DAT file that was downloaded directly or decompressed from the GZ file. The file being used to convert must be named ASTORB.DAT. If you changed the name of the file, rename it or make a copy of it with this name. Convert Click to start the conversion process Close Click to close the program. This does not cancel or reverse the conversion process if it was run. Steps to Convert the ASTORB file 1. Locate ASTORB.DAT 2. Click the Convert button 3. Close the program when done. 127 ASTORB Update This program updates the AstOrb flle so that you don’t have to download the entire ASTORB file each day. Unlike the DAILY.DAT updates for the MPCORB file, which you must get every day, the update files are dated and so you can make changes as convenient. The update files are named in YYMMDD format with either an ADD or DEL extension. Be sure to get both sets of files, especially if there is one for each date. You should still get the complete ASTORB file periodically. Usually just after the MPC releases a new set of names and the file reflects those changes. File Use the three controls at the left to locate the ADD and/or DEL files. Which files are display depends on the setting of the Mode radio group. You can select only one file at a time. Mode Select ADD button to display only ADD files. Select the Delete button to display only DEL files. Update Click this button to update the ASTORB.FF2 file with the data from the selected file. Depending on the type of file, records are either added or deleted. Close Click this button to close the form. The button is disabled while the update is running. Steps to Convert the Files 128 1. Download the ADD and DEL files from the Lowell site. If there is one of each for a given date, be sure to get both files. 2. Locate the files in the directory/file controls 3. Click the Convert button. Update Considerations 1. You can update one file at a time. This is so things are kept in step if there is a DEL and ADD file for a given date. 2. Run the update against the DEL file first. Then run against the ADD file for the same date. 3. Do the updates in date order. 4. Do not run the update using ADD or DEL files that are earlier than the last ASTORB you used to convert the entire data file. After each update, ADD or DEL, the program reassigns the internal numbers for asteroids that have not been officially numbered. This will affect any operation in the MPO Suite of programs that references the assigned number, e.g., in Canopus, the number associated with a given astrometric observation. MPCORB Conversion This program converts the MPCORB database. This program alters MPCORB.FF2. File Use this to find MPCORB.DAT.GZ or MPCORB.DAT file. As of early 2011, the Minor Planet Center supplies the MPCORB only as a DAT or GZ file. A ZIP version is not available. Canopus extracts the GZ file automatically. However, the meter showing the progress of the extraction does not move since size information is not available in the GZ file to calculate the meter’s position. New Format Check this box to convert the data to the expanded MPC format. Do NOT check this box unless and until the MPC adopts the new format. Convert Click to start the conversion process Close Click to close the program. This does not cancel or reverse the conversion process if it was run. 129 Steps to Convert the Files 1. Download MPCORB*.ZIP or MPCORB*.DAT file. 2. Locate MPCORB*.ZIP or MPCORB*.DAT file in the directory/file controls 3. Click the Convert button. The conversion also creates a file \MPO\COMMON\MPCORB_EX.DAT. This is a condensed binary version of the file that is used by MPO Connections to preload asteroid positions. If you are using MPO Connections, do not delete this file. MPCORB Daily Orbit Update Import This program converts the Daily Orbit Update files from the Minor Planet Center, placing the data into either the MPCORB or User database. The advantage of this program over the MPCORB Conversion (see above) is that the DOU downloads from the Minor Planet Center are much smaller the compressed version of the full database (a few hundred KB versus 5MB or more). File Use this to find the DAILY.DAT file you downloaded. Import Into Check MPCORB to have the imported data placed in the MPCORB data table. Check USER to have the data placed in the USERELMS data table. Empty User Check this box to delete all entries from the USERELMS data table before starting the import; otherwise the data is appended to the existing data. Exp. Format Check this box to convert to the expanded MPC format. Do NOT check this box unless and until the MPC adopts the new format. Convert Click to start the conversion process Close Click to close the program. This does not cancel or reverse the conversion process if it was run. 130 Steps to Import the DOU file 1. Download the DAILY.DAT file from the Minor Planet Center site 2. Locate the DAILY.DAT file on your computer in the directory/file controls 3. Select whether to import the data into the MPCORB or User database. If you select User, the “Empty USER” checkbox is enabled. Check this box to delete existing entries before the start of the conversion process. 4. Click the Convert button 5. Click the Close button when the conversion is done. The DOU Import does not create or update the MPCORB_EX.DAT file (see “MPCORB Conversion” above). LONEOS Conversion This program converts the LONEOS catalog of reference stars. The LONEOS file was last updated in 2009. The MPO DVD has this latest version. Brian Skiff is working on another catalog that will be more extensive and contain better photometry and positions. File Use this to find the LONEOS data file that was downloaded from the Lowell site. If you retrieved the text version of the file, select that. If you retrieved the GZ (compressed) version, you must first decompress the file to a text file before you can begin. Convert Click to start the conversion process Close Click to close the program. This does not cancel or reverse the conversion process if it was run. Steps to Convert the LONEOS file 1. Edit the LONEOS file using a text editor capable of reading UNIX format files, i.e., those with lines terminated with a single LF (#10) character. Remove all lines that are not data. Make sure there are no blank lines at the end of the file. 2. Select the file in the file list. 3. Click the Convert button. 131 User Star Conversion The User Star conversion form allows you to enter data manually from almost any catalog source. It also allows you to import data files directly, with a special provision made for sequence files prepared by Arne Henden of the U.S. Naval Observatory. The Henden files can be downloaded from the Internet. ftp://ftp.aavso.org /public/calib/ The files are simple text files and have the DAT extension. There are more than 400 sequences with more provided on a frequent basis. This form should not be used to enter data from the LONEOS catalog. There is a specific import utility for that catalog. Searching for an Entry You can search the User Star data table by name of star or Right Ascension. Sort by Use the drop down list to select the sort order of the data and to determine how to search for data, e.g., you can’t search by name when this control is set to “RA”. Search Enter the first part of the entry for which you’re looking The search is not case-sensitive but does require a perfect match otherwise, i.e., embedded spaces, etc. As you type and pause briefly, the table automatically positions itself to the nearest match. If the position doesn’t change, there is no “nearest” match. Importing Data from Files Importing data files saves a considerable amount of time when a large number of stars is involved. While the import utilities allow for a fair amount of flexibility, the text files that you try to import must follow certain rules. For Henden sequence data files, it means you must not modify the files in any way after downloading them from the Internet as the routine to handle those files depends on the data having a specific format. The rules for other data files are laid out below. Importing data from the Henden sequences adds a significant number of high quality photometric stars to the User Star data table. However, do not consider them to be photometric standards when doing the most critical of work. You might be able to use them to determine standard magnitudes for lightcurve work but you should not use them to determine standard stars in other fields. Import Data The radio button group provides two choices: “Henden Sequences” and “Other”. If you select the Henden option, the Max Err entry field is enabled. 132 Max Err. This field used only when importing Henden sequences. Enter the maximum error in the V magnitude. Any star with this error or less is imported. Min. Obs. This field is used only when importing Henden sequences. It specifies the minimum number of observations for a star before its data is imported. Henden recommends no less than three and, preferably, more. Clear Table Click this button to delete all entries in the file before importing data. Canopus does check for duplicate entries during an import so it’s not necessary to clear the table each time. You may want to clear the table if you believe one or more of the sequences have been revised so that the new data can be included. When the conversion process is complete, the data is displayed in the table at the right. Convert Click this button to start the conversion process. What happens depends on which Source Type you have selected. Importing Henden Sequences When you start the conversion with the User Star Management form, a file selection form appears. 1. Select one or more files to be converted. To select a single file, click on it in the list. To select a contiguous range of files, click on the first file and then Shift+click on the last file in the series. To select multiple files that are not contiguous in the list and without deselecting files, Ctrl+click on each file name. 2. Click the Open button to start the conversion. Converting User Star Data from Other Catalogs To import data from other catalogs, select “Other” in the Source Type radio group and then click the Convert button. The Max. Error field has no affect when importing from other sources. The Star Data Import Form allows you to specify which of the standard fields are available, how the fields in the text file are delimited, and the order in which the fields appear. For example, note in the screen shot above that the fields are not in the default order (the numbers in the parentheses give the default position). File Requirements Each file must contain one record per line and no other data, e.g., header or blank lines. The files must be simple ASCII text with each line terminated by a LF or CR/LF pair (ASCII #10 or #13#10). 133 Format of Fields The format for each of the required fields is the same as listed in Manually Entering and Editing Data (see below) with a few exceptions. The entries for RA and Declination can be in degrees, e.g., 234.78667 for RA instead of 15 39 08.8. The RA and Declination must use the same general format, i.e., degrees and decimal degrees or broken down into hours/degrees, minutes, and seconds. The magnitudes can be “absolute” or given as V magnitude with color indices for B, R, and I. At the very least, each record must contain the name of the star, the RA and Declination, and one absolute magnitude value (B, V, R, or I). If the B, R, or I magnitude values are color indices, any value with an absolute value less than 1 must have a leading zero, e.g., –0.27 or 0.84. Import Page Delimiters The Delimiters radio buttons are used to indicate the delimiter character used between fields. There must be a single delimiter between fields, e.g., if the delimiter is a space, there can be one and only one space between fields. Having two or more consecutive delimiters “fools” the import process into thinking there are more fields than are actually in the observation. If you select “Fixed Cols”, you must enter the number of characters per column in the “Width” field. Every column must have the same width. Fields List This is a drag/drop checklist that allows you to set not only which fields are in the import file but the order in which they appear. Selecting a Field To include a field, meaning the data is in the file being imported, click on the field so that the ‘X’ appears in the box next to the field name. To exclude a field that has the ‘X’ appearing next to it, click on the field name so that the ‘X’ is removed. To select more than one field, use the standard Windows methods of selecting multiple items in a list. To select a range of items, click on the first item and then Shift+Click on the last item in the range. To add (or remove) an item to those already selected, Ctrl+Click on the item so that the ‘X’ appears or disappears as desired. Changing the Order of the Fields The list defaults to the order of the fields in the User Star table. To change the order, select the item to be moved and then click the Up or Down arrow to change its position in the list. If you hold down the button for about ½-second, it automatically repeats so you don’t have to click the button repeatedly. If you change the order of the fields after you have imported the data, you must click the “Convert” button to have Canopus reload the file and parse it according to the new field order. When you move a field, all selected fields are deselected, except the one that you are moving. It’s best to arrange the fields in the order you want and then select the set of fields to be imported. Position Format HH MM SS – Select this option if the data for RA and Declination is in hours/degrees, minutes, and seconds format. For example: 04 15 07.87 +03 07 16.2 134 Note the leading zeros that keep the format of the values aligned with the required input mask. Note also that RA must have two decimal precision in the seconds and that Declination must have one decimal precision in seconds. Degrees – Use this setting if both the RA and Declination are expressed in degrees. The import process automatically converts the values to the HH MM SS format style strings. Force Landolt STD True Check this box to force the Landolt Std flag to True for all stars being imported. This saves having to manually enter a value in the text file. Force SDSS STD True Check this box to force the SDSS Std flag to True for all stars being imported. This saves having to manually enter a value in the text file. Generally, all SDSS coming from their web site or from papers establishing the SDSS system are standard stars, so this box should be checked. CI Values Check this box if the B, R, and/or I magnitudes in the file are color index values, e.g., B-V, instead of absolute values. Load Click this button to display a file open dialog that allows you to select one and only one file for importing. When you load a file, it is automatically converted, with a text display of the file shown on the Import page and the converted data as it will be entered into the User Star table on the Data page. Convert Click this button to reconvert the data read from the import file. This would be required if you change the order of the fields, which fields are selected, etc. Data Page The Data page shows the data as it would appear in the User Star table if actually copied. This provides a final check to be sure that the conversion settings are correct and that the imported data follows the format rules. Sort Use this drop down list to sort the data by RA or Name. Search for Enter a value appropriate to the Sort selection to search for a given entry. For example, if the Sort order is RA, then enter a RA value, making sure to use leading zeros and spaces between the hours and minutes and minutes and seconds. As you type and pause for a moment, the table is automatically positioned to the entry that most closely matches what you’ve entered. 135 OK Click this button to import the data into the User Star table. You are asked to confirm the request. Click Yes to import the data. Once the import is finished, a message appears on the bottom status bar telling you how many records were read and how many records were actually imported. If the numbers are not the same, the program found an error in the formatting of the data and rejected the entry. Manually Entering and Editing Data You can manually enter data and edit the data that is already in the table using the table control at the right side of the form. Editing in the Data Table To edit an existing star’s data, double click on the cell to be edited or highlight the cell and press F2. This puts the table in edit mode. You can also highlight the record and click the button on the navigator bar with the triangle. Click the navigator button with the checkmark to save the record. Click the navigator button with the ‘X’ to cancel the edit. If you move to another row while editing, the record that was being edited is saved. If you move to another column in the same row that is being edited, the record is not saved automatically. You must save the record as indicated above. Data Table Columns Some of the data in the table requires very specific formatting. Be sure to enter the data correctly. Name Enter up to 20 characters for the name of the star GSC If known, enter the GSC region and number in RRRR-NNNN format, where RRRR is the four digit region number and NNNNN is the star number with in the region. Use leading zeros to fill the entire field. For example: 0002-0033. RA Enter the J2000 RA of the star in HH MM SS.ss format. Use leading zeros as needed. Be sure to include a space between the hours and minutes and between the minutes and seconds. For example: 02 14 03.22. Dec Enter the J2000 Declination of the star in ±DD MM SS.s format. You must enter the ‘+’ or ‘–‘ and use leading zeros. Be sure to include a space between the degrees and minutes and between the minutes and seconds. For example: -03 05 32.5. B/V/R/I/g’/r’/i’ Enter the magnitudes for the star. Note that these are not color index values for the B, R, I, g’, r’, i’ but the converted magnitudes. If the magnitude for a given band is not available, enter 99.999. 136 The color index is not used to be compatible with the format of other star catalogs in the MPO Suite. B = (B-V) + V R = V – (V-R) I = V – (V-I) LStd Check the box if the star is a Landolt standard star, e.g., from the Johnson or Landolt catalogs. SStd Check the box is the star is an SDSS standard. Managing User Elements The User Elements form can be used to manually add, edit, or delete orbital elements from the USERELMS table. This includes asteroids or comets. You can enter the elements one at a time or do a batch import of files that follow the MPC standard formats for asteroids (MPCORB) or comets (e.g., the file you can download from the Minor Planet Center at http://www.minorplanetcenter.net/iau/MPCORB/CometEls.txt), or a file that uses a custom format as long as it contains the necessary information. Table The table displays the elements by Number and Name. Note that un-numbered asteroids and comets from the MPC files are given the number 0. If you import a custom set of elements, be sure not to have numbers that conflict with MPC numbers that might be in this table. Elements This section lists the elements for the selected object. The data conforms to the MPC format in terms of available values and number of decimal places. The Name field entry must be unique for every object in the table. Since multiple entries may be numbered 0, this is only way to assure uniquely finding and using a set of elements Add Click to add a new set of elements. The Edit and Delete buttons are disabled and the Yes/No buttons are enabled. Post Click to accept the set of elements being added or edited. This button is disabled until you click the Add or Edit button. Cancel Click to cancel editing the set of elements. This button is disabled until you click the Add or Edit button. 137 Edit Click to edit the currently selected set of elements. The Add and Delete buttons are disabled while the Post and Cancel buttons are enabled. Delete Click to delete the currently selected set of elements. MPC / Custom This radio group selects the format for the elements to be brought in through batch process (loading a file to read multiple elements records). Asteroid The file contains elements in the same format as the MPCORB or DAILY.DAT files. Comet The file contains elements in the same format as the CometEls.txt file that can be downloaded from the MPCORB page on the Minor Planet Center website. Custom The file contains elements in a custom format. In all cases, there should be no header lines or blank lines anywhere in the file. Each line in the text file should be one set of elements, i.e., all the data for a single object. Batch Click this button to load a text file if “Asteroid” or “Comet” is selected in the MPC/Custom radio group. If “Custom” is selected, a form appears to define the format for the incoming data. See “Batch Importing” below. Search Enter the first part of the entry for which you’re looking The search is not case-sensitive but does require a perfect match otherwise, i.e., embedded spaces, etc. As you type and pause briefly, the table automatically positions itself to the nearest match. If the position doesn’t change, there is no “nearest” match. Close Click to close the form. If you are adding or editing a set of elements, a message is displayed telling you to save or cancel the edit before closing. 138 Batch Importing The MPCORB DOU utility described before is much more efficient for importing files that fit the MPCORB format. However, you may get a set of orbital elements that are not in that exact format. You can very likely import them into the UserElems file. Click the Batch button to display the Batch User Elements form (the Import form). This form allows you to specify the fields and their order in the file as well as some other definitions that allow Canopus to parse the data. The file must contain only data lines (no headers or footers). One line must equal one record and the structure of each line must be identical – the same number of fields in each line. Delimiters Select the radio button that defines how the fields on a line are separated. If “Fixed columns” is selected, use the “Width” field to define the width of the fields, in characters. If “Space” is chosen, the number of spaces can be arbitrary. Internally, Canopus strips all trailing and leading blanks and leaves only one between the end of one field and the start of another. Base Name If the incoming data have no names, you can give them a base name that is automatically appended with an autoincrement number such that the names are unique. If the incoming data provide names, leave this field blank. Per JD Type This is the format of the Perihelion data, if in the file. JD The value is the full Julian Date (not MJD!). Offset The value is an offset from a given value. If this is selected, entered the base value in the “Base JD entry field immediately below this group. Packed The date is given as an MPC-format packed date. If the incoming data are MJD, select Offset and use a base JD such that the value in the file plus the BaseJD gives the non-modified Julian Date. This usually means having a base JD with a 0.5 fraction, e.g., 2400000.5. 139 Epoch JD Type This is the format of the incoming Epoch, the date for which the osculating elements are computed, i.e., the date on which the Mean Anomaly is the given value. The format selections and considerations are the same as for the Perihelion Date. Fields List This is a multi-select list box. Use the Up/Down arrows to put the fields in the same order as the fields in each line of the incoming file. Check the boxes for which data are available. The order and which boxes are checked are remembered so that you don’t have to redo them the next time you import data, unless the incoming data format changes. Load File Click this button to display a file dialog. Locate and select the data file to be imported. The List box below the button shows the data as interpreted by Canopus. Confirm that the file was correctly parsed. Import Click this button to transfer the records to the UserElems file. A message appears asking if you want to remove all existing records. If you answer “No”, the new data are appended to the existing data. 140 MPO Canopus Utility Programs The following section describes the utility programs within Canopus, not including PhotoRed. These utility programs enhance the use of Canopus as well as provide specific data entry functions beyond those required for asteroid and variable lightcurve analysis. These include orbit determinations, visual double star measurements, searching for new moving targets and variable stars in sets of images, and computing the absolute magnitude and phase slope parameters for asteroids. These programs, in combination with the previously described features make MPO Canopus a very powerful tool for astronomical research involving CCD images. 141 142 The Orbits Utility The Orbits Page computes preliminary orbital elements for objects using any one of several methods. These elements can be saved and then used in other MPO programs to generate ephemerides or finder charts. Determining Elements from Positions There are many methods available for determining the elements of an orbit from positions. The Orbits routines use commonly used and accepted methods to determine the initial elements from a set of observations. Depending on which initial method you select, this means having a minimum of from two to four observations. If only the minimum number of required positions is supplied and they cover not too short or long of an arc, i.e., a few days or weeks, the program should be able to find a preliminary set of elements. However, even the best of programs can return totally absurd results, e.g., an eccentricity of 3 for a main belt asteroid. This could be due to among other things, one or more observations being of dubious quality or just the right geometry of positioning among the earth, sun, and object. Note, too, that even providing the minimum number of observations, accurate as they may be, may not be enough. If that's the case, the usual remedy is to get more observations that extend the observed arc by several days and using the observations from the extreme ends of the arc along with one or two from the middle to get the minimum number for a particular method. The only exception is when using the Vaisala method. This requires only two positions but does make some very broad assumptions. See Generating Elements for more information. The more accurate positions you can supply that are still confined to a reasonable arc, partly to eliminate the need to consider planetary perturbations, the better the element set that can be found. This is because Orbits uses the extra observations in a multivariate least-squares routine to compare the M-C values (observed minus calculated position) in RA and Dec. and "plays" with the elements to find a set that minimizes the so-called residuals. Even then, it's very possible that the resulting orbit is not the orbit. As has been noted elsewhere, the same set of observations under the right circumstances, even in the hands of professionals, can yield at least two orbits: one for a main belt asteroid and the other for an asteroid that comes very close to earth. Only after the object is observed for a long period, two or more oppositions, or there is a large body of accurate positions, can a well-determined orbit start to be established. The Orbits Page The Orbits page is used to enter observations and choose the method of orbit determination. If elements can be found, they are displayed in the section just below the area where positions are entered. Also, all positions marked as used are "back-fitted" to those elements to compute the residuals of the observed minus calculated positions. The results of those calculations are shown in the bottom portion of the form. 143 Not all of the controls to the right side of the form are enabled at all times. Some are disabled until you select a particular method of orbit determination while others are enabled only when the program has found a set of elements. Observation Data Use this section to add, modify, or delete an observation from the list used to determine an orbit. See below for details about each field. Initial Method Type This radio group determines which method is used to find the initial elements set. The first three use a multivariate least squares approach to refine the initial set further. The Vaisala option uses only two observations under some broad assumptions and generates a "search window" for future observations. Buttons Save Saves the current set of observations for use later Load Loads a previously saved set of observations Clear Clears the current list of observations. Gen Generates elements Save Save the current elements set to the user database Print Send the list of observations and elements to the default printer 144 Orbits - Setting the Initial Method There are four options available for finding the initial set of elements. Only the first three use the least-squares method to try to refine the orbit. 3 pos This implements the traditional Gaussian method using three observations. Unless you know you're working with a comet that has a nearly parabolic or hyperbolic orbit, try this method first. This method works best when the initial set spans a few weeks but can be used on shorter periods. It can fail under certain geometrical situations, in particular if the orbit has a very low inclination. 4 pos This is a modification of the Gaussian method that tries to circumvent the geometrical restrictions of that method, including low inclination orbits. Try this method if you have an additional observation and the 3 pos method either fails or produces strange results. Parb This assumes a parabolic orbit, i.e., an orbit with an eccentricity of exactly 1. This is not likely but it does provide a good starting point when determining the initial orbit for a newly discovered comet. Vaisala This implements a variation of the method of Vaisala. It assumes that one of two observations has the object at the perinode of its orbit. Doing this eliminates several considerations at the expense of accuracy. However, it is very good for determining a "search window" for a few days or, at most, a few weeks removed from the initial observations. For example, the next new moon, at which time additional observations can be made and one of the other methods used to find a more reliable orbit. Orbits - Finding an Orbit Click the Gen button to find an orbit using the selected method and list of observations. If you are using the 4Pos method, a message box appears as the calculations begin. This provides the method with an initial "guess" for the object's distance. Yes Click for almost any object save one that you have good reason to believe is 1.5 AU or closer to Earth. If nothing else, try both and see which approach provides the smallest residuals. No Click to use a default value of 1.0AU. 145 If successful at finding an orbit, the program automatically enables the second tab and displays the elements. It is possible to find a set of elements that are considered unreliable. If so, one or more error messages appear while the program is finding the initial orbit. Orbits - Generating Elements To generate a set of elements requires two primary steps 1. Enter the set of observations 2. Select the method used to find the elements 3. Once you have given this information, the program can generate a set of elements. Entering Observations Date Enter the UT date of the observation UT Enter the Universal Time (in 24 hour format) of the observation. For highest accuracy, this value should account for "light time", i.e., the time it takes for light to leave the asteroid and reach earth. Of course, this requires knowing the distance of the asteroid. Barring this, use uncorrected time. The difference will not be significant in initial orbit determinations. When a well-determined orbit is required, the correct time becomes critical. If working with an observation that is expressed as a day and fraction, e.g., 27.3384, press F9 when in the UT field. This displays a popup calculator. Enter the fractional part of the day (0.3384) and then press <Enter>. The calculator closes and the value converted to hours, minutes, and seconds is entered in the field. RA Enter the Right Ascension, in the epoch of observation, in HH:MM:SS.ss format using leading zeros. Dec Enter the Declination, in the epoch of observation, in ±DD:MM:SS.s format. Epoch Enter the epoch of the observations. If the positions are measured using a star catalog with J2000 coordinates enter 2000. If you used positions from a catalog based on a different epoch, use that epoch, e.g., if 1950 enter 1950. You should not try to precess the positions beforehand. Let the program do that work for you. Init Check this box if the observation is to be used as one of those required for the initial determination of orbits. If you check more observations than are required for the chosen method, the program takes the first however many it needs. This could mean that instead of using a set of observations with a good spread in time, that you use a set separated by very short intervals. If you check this box, the Used box is automatically checked. 146 Used Check this box if the observation is to be used in the calculation of the orbit, be it as one of those required for the initial orbit determination or as part of a least-squares refinement of the initial elements. If you uncheck this box, the Init box is automatically unchecked. About Positions and the Effect on Finding Elements To find the best possible elements, if any can be found at all, the positions entered in the list must be on the same reference as the positions used internally for the Sun. As mentioned above, light-time also can play a critical role. The elements finding routines all use J2000 geocentric positions for the Sun. Therefore, the positions for the object must also be geocentric. If you enter your observations without this correction, there can be a small but significant difference due to parallax that affects the final results and may even prevent a solution from being found. If the asteroid is more than 0.5 AU away from earth, you should apply a correction to the time of the observation so that the time provided is for when the light left the asteroid (the true position being measured) and not when its light reached earth. The correction is approximately UT - 0.00572d * distance from earth in AU For example, if the asteroid is exactly 1 AU from earth, you would subtract 0.00572 days from the measured UT, or about 8.3 minutes. The List of Observations The list of available observations is displayed in the list box on the bottom portion of the first tab. As you use the cursor keys to move up and down the list (or click on one with the mouse), the position entry controls are updated with the information for the highlighted observation. In the "Init" and "Used" columns, a 'Y' indicates the item is selected for that particular purpose. A 'N' means the observation is not used for the particular purpose, e.g., a 'N' in the "Init" column means the observation is not in the set of those used to find the initial orbit. Add an Observation Enter the data in the entry fields and click the add button. Delete an Observation Highlight the observation to be deleted in the list. Then click the Delete button. Edit an Observation Highlight the observation to be modified in the list. Its values appear in the data entry fields. Change the values as needed and then click the Modify button. Orbits - Analyzing the Results Name Enter a name up to 20 characters long if you plan to save this set of elements to the user elements database for use in other MPO programs. If there are entries in the user elements database, you can select one of those names from the drop down list of the combo box. 147 H For asteroids, the H value is the magnitude of the asteroid at a fixed distance from the Sun and Earth. For comets, use the Sun distance parameter in the standard comet magnitude formula. G For asteroids, this is the phase coefficient, which takes into account that most asteroids get brighter towards opposition than would be expected from a Earth-Sun distance only based formula. For comets, enter the Earth distance parameter provided in the standard comet magnitude formula. Anom The mean anomaly, in degrees Per The argument of perihelion, in degrees Node The ascending node, in degrees Ecc The eccentricity of the orbit Incl The inclination, in degrees Axis The semi-major axis, in astronomical units Osc Date The Julian Date for the date of osculation The Residuals The bottom section shows the original observations and the M-C residuals for each position based on the derived elements. If the original epoch for any position was not 2000, the Right Ascension and Declination were converted, to J2000 coordinates before the orbit was computed. This is because the sun positions, required in the calculations, are in that epoch. The revised positions are displayed in the list and saved. If you want to preserve the originally entered positions and epoch, be sure to save them before you compute the orbit under a different name. Date / UT These are the Universal Date and Time of the observation. RA/Dec These are the J2000 RA and Declination of the observation. RAR/DCR These are the M-C residuals. The RA is corrected for cos(declination) and so is in arcseconds instead of seconds of time. 148 In the above example, the size of the residuals is significant. This could indicate any number of possibilities, e.g., one or more observations is not accurate or the geometry was such that a better solution is not possible. You can try changing which observations are used to determine the initial orbit or exclude one or more observations from the calculations entirely. When an observation has been eliminated, the residuals appear as 'n/a' in the list. The exception is when the Vaisala method is used. In this case, all residuals are listed at being 0.00000. Orbits - Vaisala Orbits If the initial method was the Vaisala method, go to the Vaisala page to generate a search window. Future Date Enter a date not too far removed from the original observations and click the Gen button. This creates a display similar to one shown above. The box with the dashed outline shows the region bounded by a set of positions based on several minor variations of the original orbital elements. The odds of finding the object on the specified date within the window are usually very good. 149 150 The Moving Object Search Utility The Moving Object Search (MOS from here on) scans groups of three images to search for objects that appear to be moving in a linear motion. The search parameters can be defined so as to limit the amount of motion, the tolerance of the linearity, and the faintest object both in terms of raw instrumental magnitude and strength of the object signal above the background noise. To run the Moving Object Search utility, select Utilities | Moving object search from the main menu. To get the best possible results, the images that are searched should be processed with at least a dark frame and, highly recommended, a flat field. How the MOS Works As always, it’s a good idea to understand at least a little of how a routine works so you can have a better understanding of the results and how to get the most out of the routine’s potential. Following are the basic steps in the MOS process Select one or more groups of three images. Three images are required to determine linearity of motion and to help assure that the object is real. Even so, there can be numerous false hits. For each group, Canopus uses the SEXtractor program to extract stars from the image (see Credits). The search parameters help determine which “stars” in the image included in the output. The data for each image is stored in an internal list. The three lists are associated with the given group. Each group as a separate entity. Once the three lists are created, images 2 and 3 are matched to image 1, i.e., for each star in image 2 and 3 Canopus determines what the X/Y position of the star would be on image 1. It does this by using a “constellation” of stars from image 1 and finding the best possible match to that constellation on images 2 and 3. From this matching, Canopus is able to determine the X/Y offset for each star in image 2 and 3 to make it match the same star on image 1. In some cases, e.g., image repositioning, the star is missing from image 1 or one of the other two. As result, stars on images 2 and 3 can have negative X and Y values. For each group, the three converted lists are then placed into one master list (keeping track of from which image each item in the master list the data came). Canopus then iterates through the list finding sets of stars that have the same image 1 X/Y coordinates (be they from image 1 or the transformed values from images 2 and 3). Think of the process as superimposing the three images on top of one another and removing from the resulting im- 151 age all stars that were built from two or more stars in the original three images. What’s left are, supposedly, stars that were not in the same position (relative to image 1) on the three images. Canopus then iterates through the filtered list looking for any combination of three stars such that the difference in X/Y position between star 1 and star 2 and between star 2 and star 3 meets the linearity test. Specifically, 1) that the three points line on a line within the tolerance set for the search; 2) the ratio of distances between point 1 and 2 and point 2 and 3 versus the total distance are the same as the ratio of the time between image 1 and 2 and the time between image 2 and 3 versus the total time between image 1 and 3. For example: if image 2 was taken five minutes after image 1 and image 3 was taken 10 minutes after image 2, then the distance the object moved from image 1 to image 2 must be one-half the distance it moved from image 2 to image 3. If a set of three “stars” (one or more could be conveniently placed clumps of noise) is found, it is added to a master list of potential targets. After all possibilities are searched, Canopus displays the results, where you can review the images with the object highlighted and determine if the object is real. As part of the final result, Canopus prepares an MPC compatible report that you can edit after reviewing the images. In order to generate the MPC report, Canopus must be able to match a chart to each image so that it can reduce the image and so find the RA and Declination based on X/Y coordinates. This requires that you have the correct configuration settings just as if you were doing automatic astrometry in Canopus. See “What is Chart Matching?” and the subsequent sections for more information about matching an image to a chart for astrometry. Using the MOS The Users Guide “Supplemental” chapter has a complete tutorial on using the Moving Object Search. Refer to that document for instructions on searching for moving objects. Below is a more detailed description of the input parameters for the search. MOS - Setting the Search Parameters Before starting the search, you must tell Canopus some of the parameters it uses to extract stars and to search for linear motion. Those parameters are set on the Select/Extract page of the MOS form. 152 Search Floor Enter the faintest magnitude to be extracted to the search lists. Note that this is instrumental magnitude, since that is what the extraction code provides. Therefore, as a star gets fainter, its instrumental magnitude is less negative and approaches 0. For example, –10.000 is brighter than –9.000. This is the same as the sky magnitude system, it’s just that all stars in the instrumental system have negative values. FWHM (pix) Enter the full-width half-maximum width of an “average star” on the images, in pixels. The SExtractor code uses this to help separate merged stars. Apertures Click this button to change the aperture settings for measuring objects. Only the measuring aperture (the inner most setting) is used to modify the SExtractor parameters. MPC Click this button to display the Canopus configuration so that you can change the settings on the MPC page. These are inserted into the top of the MPC report that the MOS generates. Min. sigma Enter a value to indicate the how strong the star image is compared to the immediate background. The value is in sigmas of the background noise. One sigma implies a standard deviation of about 68%. For example, if you set this value to 1, you’re asking to find stars where the star signal is about equal to the background noise plus one-sigma of the background noise. You can enter values of < 1.0. This helps finds objects just above the background noise. Going too far, however, results in a large number of false hits and, if taken to extreme, would mean that just about every pixel on the image could be considered a target. Tolerance Enter the number pixels a star’s centroid can vary from linearity. This applies two ways. First, the point must be within Tolerance number of pixels of a line joining the other two stars. If the point is beyond the two points, e.g., star 3 would be beyond the line joining stars 1 and 2, Canopus extrapolates the line from 1 to 2 out to the star 3 position’s proximity. The second linearity test is based on the ratio of distance traveled versus over all time. Say the time between images 1 and 2 was one-half the time between images 2 and 3. Perfect linear motion would have the star move twice the distance between the image 2 and image 3 position as it did between the image 1 and image 2 position. The tolerance specifies by how many pixels from the extrapolated or interpolated motion the position can vary and still be included. If you think there are faster moving objects in the field, set this to a higher tolerance. Doing so will result in more false hits but it’s better to reject bad objects than lose real ones. Max. motion (pixels) Enter the maximum number of pixels the object can move from image 1 to image 3. This helps filter out some hits that are the result of random alignments that appear to simulate linear motion. It can also filter out a fast moving object if the value is too small. Again, compromise is the order of the day. Mag Code Select one of the supported magnitude bands or “Do not Use” from the drop down list. If you want to include magnitude estimates in the report, you must select one of the supported bands (BVRI, SDSS griz). Generally, you will select the same band that you have selected for the Canopus Configuration | Photometry | Default Band since this is the band from which magnitudes were taken from the catalogs to establish the M/IR and estimate the object’s magnitude on the Reductions page. 153 It’s easier to erase than add later, so it’s recommended that you select a band and, if you don’t want to include magnitudes in the MPC report, delete them from the report before sending. If using a Clear filter, the ‘R’ band is recommended for the Default Band and this setting since many of the popular cameras when unfiltered favor that band. Of course, if you used a filter, you should select its band in the configuration and here. Save Dir. Enter a complete path to an existing directory to where the extracted star data is saved. The data can be displayed in the read-only memo on the right side of the page. This same directory is used to store the MPC compatible report generated at the end of the search. If you don’t want to type in the name or are not sure which directories are available, use the speed button to the right of the field to display a directory locator form. Extracted Files The listbox displays the list of files created during the extraction process. Double click on any one of the entries to display the contents of the file in the read-only memo on the right side of the form. Delete Click this button to delete the extracted star data files. The extracted star files are simple text files with the DAT extension. The MPC compatible reports are named AUTOMEASURExxx.EMF, where xxx is a unique number. Be sure to delete these files from time to time or you’ll use up disk space very quickly. MOS - Reviewing the Results Results – Extracted Star Data Once the search is finished, you can review the extracted star data. On the Select/Extract page, double click on one of the files in the list at the lower left. The data from the file is displayed in the read-only memo at the right. The columns, in order, are: Number X Y Mag 154 An arbitrary number assigned to the star The X centroid for the star The Y centroid for the star. The instrumental magnitude of the star Flag A integer value that indicates the quality of the measurement. 0 means the star was not too near an edge, was not involved with another star, was not saturated, etc. You can sort the data by the values in the X, Y, or Magnitude columns. Click on the header for the column by which you want to sort the data. The data is arranged in ascending order. Click on the same column again to sort the data by descending order. Results – Potential Targets The Results page contains two sections. The Potential Targets section on the left has two “tree view” controls. The top control shows the groups with the potential targets in each group a “branches” of each group. The other section, on the right side of the page, displays the images associated with a given target with a circle drawn around the target. To Display Details for a Given Target Expand a group by clicking on the ‘+’ next to its name. Then click on a target underneath that group. After a brief pause of about ½ second, the display in the lower tree view is updated to show information about the three images associated with the target. As shown above, you can expand the branches of this control to display the details for each image. These include: Date of image from header Time of image from header X Centroid of target on image Y Centroid of target on image When you click on one of the image names (branches) in the lower control, the associated image automatically loads after a short (½ second) delay. By reviewing the images, you can determine if the target is or isn’t real. If there’s doubt, then human judgment determines if you include the target in a report to the Minor Planet Center. 155 Results – MPC Report The MPC Report page shows an MPC compatible report generated from the list of potential targets. This is the same MPC report editor that is used during astrometry in Canopus. See Creating an MPC Report in the Users Guide for more information. Sometimes the number of lines on this page won’t be exactly 3x the number of objects found. The most common reasons for observations missing from the report are that 1) Canopus could not match a given image and so do an astrometric solution for the object or 2) a good centroid could not be found when trying to measure the position after finding the plate constants for the image. The first cause of failure is often due to bad configuration settings that don’t reflect the size of image correctly (pixels per row/column and/or pixel sizes) or the focal length. Canopus tries to use the settings from the images but if the focal length in the header differs too much from the one in the configuration, the configuration setting wins out. Thus, you should make sure that you configuration settings are accurate for the set of images being measured. For the second cause for objects not appearing, it’s usually because the “object” was really a cosmic hit or hot pixel. SExtractor finds a “star” if there are five or more pixels in it. When Canopus goes to measure the object, it adds a test that each pixel that is sufficient above the sky background has at least three immediate neighbors that are also above the sky background. This is almost never the case for a cosmic ray hit or random hot pixel. 156 The Variable Star Search Utility The Variable Star Search Utility (the VSS) scans a set of images, all of the same field, looking for possible variable stars. When working the same field all night, as with an asteroid that’s not moving too fast or a variable star, there is no small possibility that at least one other object in the field is variable. This routine helps identify those possibilities so that you can do more precise photometry if it seems warranted. The VSS does not measure moving targets. Users Guide Tutorial The Users Guide has a complete tutorial on using the VSS. This section gives additional information and details on the search parameters. Two Review Methods The VSS provides to methods for reviewing the data to look for variables. Mean Magnitude and Standard Deviation 157 This method, the results being displayed on the Results (Mean/SD) tab, finds the mean (average) magnitude for every star found on the set of images, i.e., its magnitude is summed over all images and the average is found. At the same time, the standard deviation of the mean is computed. The mean magnitudes are plotted along the X-axis while the standard deviations provide the Y-axis values, as shown in the screen shot below. The brightest stars are on the left and the faintest are on the right. With enough stars, you’ll see that the standard deviation (scatter) is high at the left (saturated stars) levels off at bottom for the middle, and then increases again towards far right (stars just above the sky background). The logic behind this method says that stars of similar magnitude will have about the same standard deviation. However, a variable star will, of course, have a higher standard deviation because its magnitude varies more than just the general scatter. Such a point is at about (0.5, 0.18) in the plot above. Any point that is "sticking out from the crowd" that is not towards the extreme left or right is a good candidate for a variable. Simple Data Review This method is the original one used in the VSS. Here, stars are filtered by the amplitude, which could be real or simply due to excessive scatter. Those stars having amplitudes in the range specified in the search are added to a list on the Results (Targets) tab. On that page, you click on a given suspect to display a plot of its data and location on the reference image. It's up to your judgment to determine if a given star is a variable. As you review the targets (especially if there are many), you'll see a general trend in the curves, indicating they were all affected equally by minor errors in the comp star values or some other problem. It's when a plot shows a significant change from the general trend or, if you're lucky, a nice sinuous curve as in the plot above, that star becomes a likely candidate. To get the best possible results, the images that are searched should be processed with at least a dark frame and, highly recommended, flat fielded. How the VSS Works As always, it’s a good idea to understand at least a little of how a routine works so you can have a better understanding of the results and how to get the most out of the routine’s potential. Following are the basic steps in the VSS process 1. 158 A series of images is specified as well as the search parameters. 2. Canopus uses the SEXtractor program to extract stars from the images (see Credits). The search parameters help determine which “stars” in the image included in the output. The data for each image is stored in an internal list. 3. Once the image lists are created, all images from 2 to N are matched to image 1, i.e., for each star the images, Canopus determines what the X/Y position of the star would be on image 1. It does this by using a “constellation” of stars from image 1 and finding the best possible match to that constellation on the other images. 4. From this matching, Canopus is able to determine the X/Y offset for each star in the images to make it match the same star on image 1. In some cases, e.g., image repositioning, the star is missing from image 1 and some of the other images. As result, stars on those other images can have negative X and Y values. 5. The iteration through the list of images performs a second task. If the image is image 1, Canopus finds a set of 10-20 reference stars to be used for differential photometry on the remaining images. The star in this set must “clean” in that they are not too near the edge, involved with other stars, saturated, etc. This same set of reference stars is used on every image. 6. For images 2 through N, Canopus finds the reference stars, computes the average magnitude, and then computes the differential magnitude of every star extracted from the image that is brighter than the userspecified limit. The differential values are stored with each star for each image. 7. The converted lists are then placed into one master list (keeping information about from which image each item in the master list the data came). Canopus then iterates through the list finding sets of stars that have the same image 1 X/Y coordinates (be they from image 1 or the transformed values from images 2 and 3). If the same star is found on the user-specified percentage of images, Canopus creates a “container” for that star and stores information about each measurement in that container. 8. After all the “containers” have been created, Canopus stores the data for each one for use on the MeanSD tab. At the same time, the data for a given "container" (variable star candidate) are reviewed to see if the amplitude of the observations meets the minimum requirements of the search parameters. If so, those variables are loaded into the list on the Targets tab. In the final search for results, the first image in the list is “discarded”, since it provided the reference positions and, more important, reference photometry stars. In the following discussions concerning “the first image on which the star was found,” the first possible image is actually the second image in the series of images you selected. There’s No Substitute for the Real Thing The VSS is intended to help you find variable stars. As noted in the next section, you can create data files of JD/magnitude pairs to import directly into Canopus. This does save the time of remeasuring images. If the results do seem reasonably “solid”, then it is probably acceptable to use this timesaving feature. However, the search cannot always do critical analysis. For example: The process cannot fully control which stars are included based on being involved with other stars. The process cannot fully recognize when a particular image should not be measured, e.g., cosmic hit, image defect, too near the edge, etc. These factors can be controlled to a much higher degree using the more rigorous photometry features of Canopus, specifically the Lightcurve Wizard. If you have doubts about the measurements, you should measure the images again. This is not as bad as it seems. If images are reasonably well aligned through the night (and there’s little reason they shouldn’t be), then you can use the wizard to measure images at the rate of 500–700 an hour. That’s better than most automatic procedures and you can have far more confidence in the initial results and spend far less time refining those results during lightcurve analysis. 159 VSS - Search Parameters The search parameters define the limits of what Canopus returns in the results and where extracted star data is stored. Search Floor Enter the faintest magnitude to be extracted to the search lists. Note that this is instrumental magnitude, as that is what the extraction code provides. Therefore, as a star gets fainter, its instrumental magnitude is less negative and approaches 0. For example, –10.000 is brighter than –9.000. This is the same as the regular magnitude system, it’s just that all stars in the instrumental system have negative values. FWHM (pix) Enter the full-width half-maximum, in pixels, of an “average” star on one of the images. SExtractor uses this to help separate close stars and/or galaxies. You can find the FWHM of a star by opening an image and clicking on a representative star. The SNR/FHWM/MaxPixel values are reported in one of the status bar panels at the bottom of the main form. Min. amplitude Enter a value to indicate the minimum range of the measured instrumental magnitudes. This setting is use to filter the entries that appear on the Results (Target) tab. All stars that are above the floor are included in the Results (Mean/SD) tab. Min. S.D. Enter the minimum standard deviation to be included in the MeanSD plot. By setting a minimum value greater than 0, you eliminate stars that are very unlikely variable. To estimate the standard deviation for a given total amplitude of a curve, use the formula SD = Amplitude * 0.707 This is derived from the fact that a simple sine wave with total amplitude of 2 (+1 to –1) has a standard deviation of 0.707. So, if you set the minimum amplitude to 0.1mag, that corresponds to a standard deviation of 0.071. To be safe, you would probably use a value slightly lower than this, e.g., 0.050. Max. S.D. Enter the maximum standard deviation to be included in the MeanSD plot. This sets an upper limit and so filters out fainter stars by the fact that their standard deviations tend to be higher because the measurement of stars just above the noise has considerable uncertainty. Use the formula given under "Min S.D.", using a maximum expected amplitude instead of minimum. 160 While setting this value may help eliminate false hits due to faint stars on the MeanSD plot, it could also exclude a large amplitude variable of any magnitude. Since you can run the search again without having to extract the data from the images, use a large value, e.g., 1.0 (more than a 2.0 mag total amplitude) for the first pass. Min % of image Enter the minimum percentage of the image in which a given star must appear to be included in the results. This helps filter random noise and stars that drift in and out of the images because of poor tracking or repositioning. Save Dir. Enter a complete path to an existing directory to where the extracted star data is saved. The data can be displayed in the read-only memo on the right side of the page. This same directory is used to store the MPC compatible report generated at the end of the search. If you don’t want to type in the name or are not sure which directories are available, use the speed button to the right of the field to display a directory locator form. Create Canopus Import Files Check this box to have Canopus create a file of JD/magnitude pairs for each variable found. This file can be imported into a Canopus session, saving you the time of remeasuring the images. The file contains X/Y information for the (up to) five comparison stars in the first five lines. The information can be used to create more detailed comp star entries in the session. These lines must be removed prior to trying to import the data. The files are saved in the directory specified in Save Dir and are named using the filename of the first image used in the search along with the name assigned to the variable and having a TXT extension. For example, assuming the first image had a name of A620_0001.FIT and the variable is Star0001, the file will be named A620_0001_Star0001.TXT Use Astrometry Component Check this box to have the VSS remeasure all the stars using the same methods used in Canopus for measuring stars on the image. These values are used in lieu of those from SExtractor. This is not generally recommended. First, it makes the search much slower and it is less discriminating in crowded fields. Extracted Files The listbox displays the list of files created during the extraction process. Double click on any one of the entries to display the contents of the file in the read-only memo on the right side of the form. Delete Click this button to delete the extracted star data files. The extracted star files are simple text files with the DAT extension. If you don’t delete the files immediately after the search, be sure to delete them from time to time or you’ll use up disk space very quickly. Saving and Using Search Results The extraction and initial search process can take some time. So, once it's done but you think you might want to work with the data again, you can save all the necessary information to do analysis at some other time. Variables List – Load Click this button to display an open file form and select a previously saved session. All files are saved with the extension of VDF (Variables Data File). Once you load the file, the focus is set to the NewComps button so that you can start a new round of analysis after picking the comp stars. See Running the Search Again (Resetting the Comps) for more details. 161 Variables List – Save Click this button after you've extracted stars from a set of images and the program has found one or more potential variables. You can (and probably should) save the data even before you begin reviewing the results. Included in the information that is saved is the full path name for each image that was included in the search. When you load the saved data, those images must be available in the exact same location. This is most important for the reference image you used originally to set the comparisons. It’s reopened so that you can specify the same, or different, comparisons to be used in the new search. Variables List - Clear Click this button to clear ALL data, just as if you had not extracted data at all. Variables List - Delete VDFs The files saved using the Save button can be very large. For example, a set of 17 images that generated more than 300 stars above the limiting lower magnitude generated a file of about 5MB. This button allows you to delete the files by bringing up a mutli-select form where you can specify one or more files in a directory to be removed. The Extraction Data Double click on any file in the Extracted Files list box to see the data in that file. The columns, in order, are: Number X Y Mag Flag An arbitrary number assigned to the star The X centroid for the star The Y centroid for the star. The instrumental magnitude of the star A integer value that indicates the quality of the measurement. 0 means the star was not too near an edge, was not involved with another star, was not saturated, etc. You can sort the data by the values in the X, Y, or Magnitude columns. Click on the header for the column by which you want to sort the data. The data is arranged in ascending order. Click on the same column again to sort the data by descending order. VSS - Reviewing the Results (Mean/SD Tab) 162 Using the Splitter Bars The Results (Mean/SD) tab has three sections. You can change how the sections are divided within the total area by moving one of two "splitter" bars. The first bar is the horizontal division between the panel holding the image and lightcurve plot at the top and the panel holding the MeanSD chart and target data box at the bottom. The second bar is the one that divides the image and lightcurve plot. To change the position of a given splitter bar, move the mouse over the bar until you see the mouse cursor change. Then depress the left mouse button and drag the bar to its new location. Release the mouse. The Image Section The image is at the upper left and displays the location of the comparison stars (red circles) and the selected target (bright green circle). If you click on any star, the green circle moves to surround that star (if you click on one of the comps, the circle is yellow). This action does several other things as well: The dot in the MeanSD chart that is associated with that star turns from black to green. The data for that star is displayed in the data box at the lower right of the page. The plot of the differential magnitudes for the star appears at the upper right The star is automatically selected on the Results (Targets) tab. The MeanSD Chart Section This chart shows the data for each star found, regardless of amplitude. The mean magnitude of the star over the set of images is plotted on the X-axis while the standard deviation of the mean is plotted on the Y-axis. See the opening section of this group of topics for how to interpret this chart. If you click on any given dot, it changes color from black (or green if you clicked on the associated star first) to red. This action does several things as well: The associated variable is surrounded by a green circle on the image. The data for that star is displayed in the data box at the lower right of the page. The plot of the differential magnitudes for the star appears at the upper right The star is automatically selected on the Results (Targets) tab. Close Quarters As you can see, the dots can be very close together, especially if you do not have the VSS form maximized. Even then, depending on the number of stars and their magnitudes, it may be hard to see the individual dots. This also means that clicking on what you think is the right position for a given dot may not change its color and perform the other steps outlined above. In this case, you need to zoom in on a small region of interest so that the dots are well separated. To Zoom Move the mouse cursor to the upper left of the region that you want to enlarge. Depress the left mouse button and drag the cursor to the lower right corner of the region and then release the button. To Pan If you have zoomed on a region and want to see other sections of the plot at the same zoom level you can pan around the chart. Move the mouse cursor to about the middle of the visible section of the plot. 163 Depress the right mouse button and drag the cursor to pan the chart in the direction you move. Release the button to stop panning. To Restore to Normal Move the mouse cursor to somewhere below and to the right of center of the chart. The exact location is not critical. Depress the left mouse button and drag the mouse cursor up and to the left by a small amount. Release the button. Even when you have zoomed in as much as possible, some dots may still overlap. If you click on the center of an overlapping pair, the chart still may not be able to determine which point was clicked. In this case, click on a point near the edge but still within the dot and which is as far as possible from the second dot. Eventually, you will be able to find a location where the chart can determine the dot being clicked and work as expected. VSS - Reviewing the Results (Targets Tab) Potential Variables List box This box shows the list of potential variables. To show the data for a given star, click on it in the list box. The data for the star is then displayed in the Image/Variable Data tree view and the notebook control at right displays a plot of the data and the first image on which the star was found. Selecting a star here automatically selects that star on the Mean/SD tab. Selecting a star here also changes the plot and image on this tab to reflect the selected star. Image/Variable Data Tree view This control displays the data for the star selected in the Potential Targets list box. Date/Time These are the data and time taken from the image header. I1X/IXY These are the X/Y coordinates of the star on the first image on which it was found translated to the X/Y coordinates it would have had on the first image in the series. CIX/CIY These are the X/Y coordinates of the star on the first image on which is was found, i.e., the image displayed in the notebook control. 164 Amp This is the amplitude, maximum range, of the data. Min/Max These are the minimum and maximum instrumental magnitudes for the star. Save Info Click the Save Info button to add the data to the memo on the Targets of Interest tab. If the star is already in the memo, it is not added again. Data Tab This tab on the notebook shows a plot of the data, i.e., a lightcurve using the differential magnitudes. In the example above, the lightcurve seems to show a nice sine wave and is very likely a variable. Image Tab The Image tab shows the image listed in the Image/Variable Data tree view. This is the first image on which the star was found. A circle is drawn about the star so that you can easily find it when doing detailed photometry. 165 166 Asteroid Browser The Asteroid Browser allows you to browse through the MPC, Lowell, or UserElems tables and generate ephemeredes for a given object. The Browser Form Asteroid Table This displays the entries in the selected table. Use the navigator bar underneath the table to move one record forwards or backwards or to the first or last item in the table. Click on an entry to select the particular asteroid. The highlight moves to indicate which asteroid is selected. Database Use this control to select either the MPC or Lowell data table for browsing. The Lowell table includes diameter and class information for some asteroids. If this table is selected, it can affect the presentation of the data for those two items in the “Asteroid Data” group. See below for more information. Sort by Use the drop down list to set the order in which the table is displayed. The available options are Name and Number. Search for If sorting by number, enter all or part of the asteroid number. After a brief pause when you stop typing, the program finds the closest entry greater than or equal to the value entered in the field. If the sort order is number, enter only numbers. If the sort order is Name, enter the all or part of the name or designation of the asteroid. If you have a filter turned on, the program may not find an entry even though you enter its number or name exactly. Filtered Check this box if you want to filter the results based on the filter string created when you use the Set Filter button. Filtering allows you to restrict the asteroids see in the table, e.g., so that you see only Jupiter Trojans or NEOs. Uncheck the box to remove filtering. All entries in the table can then be seen. 167 When filtered is turned on, the program does not scroll through the data as quickly and it may take a few seconds after checking this box before the filter takes hold. This is because the program must look at each record to determine if it meets the filter conditions. Set Filter Click this button to display the Filter form. If there is an existing filter, it is displayed immediately below the entry fields. It’s displayed in the format that is required by the database engine. Use (all filter sections) Check the box if you want the values in the given option to be part of the filter. Min/Max (all filter sections) Enter a minimum and maximum value for each orbital element that you want to include in the filter. Remember that the inclination ranges from 0° to 180° while the eccentricity ranges from 0.0 to < 1.0. The minimum value must be less than the maximum. OK Click this button to build the filter. The form is then closed. This does not automatically apply the filter, however. For that to happen, the Filtered box must be checked. Cancel Click this button to close the form and keep the existing filter, if any. Asteroid Data This section displays the orbital elements for the selected asteroid. Details about most elements are not given since it’s assumed you know their meaning. Dia The “Dia(meter)” field shows the diameter of the asteroid in km. Since most asteroids are decidedly nonspherical, this is an average value for the body. If an asterisk appears after the value, e.g., 902.07*, this means the diameter is assumed using a formula by Alan Harris using the H value and an assumed albedo based on the semi-major axis of the asteroid. Use this value as a guide only. If the MPC table is selected, the value always has an asterisk as the MPCORB file does not include diameter or class information. If the Lowell table is selected, the absence of the asterisk indicates the value is taken directly from the Lowell table. The vast majority of entries in the Lowell table do not have diameter values and so you’ll see the asterisk more times than not. 168 Class This field displays the taxonomic class of the asteroid. If there is an asterisk after the entry, then after the Harris formula, the class is assumed based on the semi-major axis with the possible values being S SC C SMA < 2.7 AU 2.7 < SMA 2.8 AU > 2.8 Assumed Albedo: 0.18 Assumed Albedo: 0.10 Assumed Albedo: 0.058 These are very broad assumptions and should used only as an approximate guide. For example, members of the Hungaria family (inner main belt) are assumed to be class E and have albedos of 0.3-0.4. Generating an Ephemeris The browser allows you to generate an ephemeris for the selected asteroid. The positions include planetary perturbations and can be either geocentric or topocentric. For the latter, this means you must have the correct longitude and latitude for your location (or the location of interest) in the configuration setup. Date Enter the UT Date for the first position. The format is determined by your Windows settings with the exception that you must enter all four digits of the year. UT Enter the UT of the first position. The format is hh:mm, using 24-hour format, e.g., 1:00pm is 13:00. Pos Enter the total number of positions to be generated. Interval Enter the interval between each position. This can be in days or hours, depending on the status of the Days checkbox. If you want positions that are integral multiples of 24 hours apart, use the number of days and check the Days box. For example, use 1.00 with Days checked instead of 24.00 and Days not checked. Days Check this box to indicate the interval is in days. Uncheck the box if the interval is in hours. Geo Check this box to generate geocentric positions. Uncheck the box to generate topocentric positions, i.e., positions as seen from the location in the configuration settings. The difference between the two can be significant if the asteroid is close to Earth. Generate (Stopwatch icon) Click this button to generate the ephemeris. The table is filled with the ephemeris data and the Print button is enabled. Table Columns Date UT RA Dec E.D. S.D. Mag PA Month/Date of position UT of position J2000 Right Ascension J2000 Declination Earth distance in A.U. Sun distance in A.U. Estimated V magnitude Phase angle. This is 0° when the asteroid is exactly on the line joining the Sun and Earth and opposite the Sun in the sky. Angular separation in the sky between the Sun and asteroid. Altitude of the asteroid. E Alt 169 Az PABLg PABLt LHel Azimuth of the asteroid. This is measured from North (0°) to East (90°), etc. Phase Angle Bisector ecliptic longitude Phase Angle Bisector ecliptic latitude. Heliocentric longitude. The Phase Angle Bisector is the point in the sky exactly halfway between the opposition (anti-solar) point and the position of the asteroid. This gives the “viewing direction” to the asteroid. The values are often given (or should be) when reporting lightcurve analysis to help those doing spin axis and shape modeling studies. LP Values Check this box to generate lower precision values for all values. For example: Higher precision DATE UT RA(2000) DC(2000) E.D. S.D. Mag PA ... ------------------------------------------------------------------------ ... 2011/06/01 00:00 10 33.92 +13 58.6 1.805 1.991 15.30 30.5 ... DATE UT RA(2000) DC(2000) E.D. S.D. Mag PA ------------------------------------------------------------------------2011/06/01 00:00 10 33.9 +13 59 1.81 1.99 15.3 30.5 Save to Text File (Printer icon) Click this button to send the ephemeris in the table to a text file. The file is automatically named “Ephemeris_XXXXXX.TXT”, where XXXXX is the name or designation of the asteroid. This button is disabled each time you move the asteroid table to a different asteroid. This is so the name of the ephemeris file matches the positions for the asteroid that was selected when you generated the ephemeris. In short, select an asteroid, generate the ephemeris, and save the ephemeris to a text file before selecting another asteroid. The ephemeris that’s saved to the text file has information beyond what you see in the table. Also included are HLat heliocentric ecliptic latitude Moon Elongation from the moon MP Moon phase (0 = New, 0.5 = Quarter, 1.0 = Full. Positive is waxing, negative is waning) GL Galactic longitude GB Galactic latitude 170 Asteroid Search With the search feature of the Canopus Asteroid Search, you can quickly find potential lightcurve targets by looking for asteroids that are above the horizon or near a specific position at a given date and time. Searches can be based on current altitude/azimuth or proximity to a given position. In short, select a type of search, set the appropriate search parameters, and then run the search. You cannot run the search in more than one instance of Canopus. Each instance uses the same output table to which there must be exclusive access at one point during the search. If you try to start a search in a second instance with the first instance of Canopus having this form open, you will get an error message about a closed data set. Types of Searches AltAz Finds asteroids above the horizon given the location, date, and time. The search can be filtered to include asteroids within a certain magnitude range, range of numbers, or minimum distance above the horizon. Photo Finds asteroids near a given position given the date and time. The search can be filtered to include those in a certain range of magnitude or numbers. The generated positions take into account planetary perturbations to increase accuracy and help identify, for example, suspects near galaxies. The results for either search are stored in separate database tables but displayed in the same viewer. Which result set is displayed is selected by the "Search Type" control. The results for a set are kept until you hit the Clear button when that set is being displayed. Search Setup Before you run a search, you must specify the type of search, some data that is common to either type, and parameters that depend on the search type. Common Parameters Date Enter the UT date for the search. The format for entry depends on your Windows regional settings with the exception that you must enter all four digits of the year, i.e., 2006, not 06. Time Enter the UT in 24-hour format using leading zeros, e.g., 13:05:00 for 1:05pm. 171 Start Enter the starting number of the range of asteroid numbers for the search. To search only numbered asteroids, set Start = 1. Setting Start = 0 first examines all un-numbered asteroids and then searches numbered asteroids from 1 – End. End Enter the ending number of the range of asteroid numbers for the search. Using this field with the Start field can reduce the time for a search by skipping certain asteroids, e.g., the lower numbered asteroids. Do not enter Start = 0, End = 0. This results in Canopus looking at only the first un-numbered asteroid. The default number in this field is the highest numbered asteroid and not the total number of objects in the selected data table. Fainter “Fainter than”. This determines the brightest asteroid magnitude included in the search. Brighter “Brighter than”. This determines the faintest asteroid magnitude included in the search. Search Type and Table The “Search Type” radio buttons determine the type of search that is run. Click the appropriate button. The “Search Database” section determines which asteroid table, MPC or Lowell, is used. Select the table from the drop down list. The “Asteroid Groups” limits the results set somewhat by letting you select a subset based on the semi-major axis of the asteroid. The eccentricity of the orbit is not considered. All NEO MB1 MB2 KBO All found objects are included in the results set. Asteroids with a semi-major axis < 1.33 AU. Asteroids with a semi-major axis between 1.30 and 2.1 AU, i.e., “inner main-belt objects.” Asteroids with a semi-major axis between 2.0 and 6.0 AU, i.e., “regular main-belt objects” Asteroids with a semi-major axis > 6.0 A.U. This includes Centaurs, Cubewanos, and everything else that goes bump in the distant night. Specific Search Parameters Each search has its own set of specific parameters. AltAz – Min. Alt. Enter the minimum altitude, in degrees, above the horizon for the object to be included the result set. Photometry – RA Enter the J2000 Right Ascension of the center of the search window. Use hh:mm:ss format with leading zeros, e.g., 04:10:00. Photometry – Dec Enter the J2000 Declination of the center of the search window. Use ±dd:mm:ss format with leading zeros, e.g., – 05:10:00 or +25:34:15. Note that you must include the plus or minus sign. Photometry – Sep Enter the radius of the search window, in degrees. 172 Running a Search The small meter control keeps you posted on the progress of the search as do the labels just above it, which show how many “hits” have been found so far. Start Click this button to start the search Halt Click this button to stop the search immediately and display the results found to that point. Clear Click this button to remove all entries for the table being displayed, i.e., if the AltAz results table is being shown, only the AltAz data is removed. Any results under the Photo table are still available by setting the search type to Photo. Sorting the Search Results The combo box at the bottom of the table of results allows you to sort the data several ways and to search for items based on the current sort order. Which options are available depend on the type of search. AltAz Search Altitude Azimuth Magnitude Name Number RA Sorts by increasing altitude Sorts by increasing azimuth Sorts by decreasing magnitude (brightest first) Sorts by object name Sorts by object number Sorts by Right Ascension Photo Search Mag Name Number Separation Sorts by decreasing magnitude (brightest first) Sorts by object name Sorts by object number Sorts by increasing separation, stated in arcseconds To Search for an Item Enter all or part of the value on which to search. For example, if sorting by name and you enter ‘C’ (without the quotes), the list is positioned to the first item that starts with the letter C. If none is found, the table remains on the current record. The search is not case-sensitive. The search does not occur until you pause for about half a second. Working with Search Results You can load previously saved results data, save the current set, and send the current set of results to a text file. Load Click this button to display a file open form and load the results of a previous search. The Date/UT fields are not updated to indicate for when the search was run. The file open form limits the files to those appropriate to the currently selected search type, e.g., *.ALZ if AltAz and *.PHT if Photo. Save Click this button to save the current search results. A file save form is displayed that allows you to set the name of the file. The extension is forced to ALZ for an AltAz search and to PHT for a Photo search. 173 Reverse Check this box to have the data saved to the text file in reverse order of the currently selected sort type. For example, if the sort order is Azimuth, the default is ascending order. If you check this box, the data is written with higher azimuths first and smaller azimuths last. This can be useful if planning a multi-target run where you want to work asteroids in the west first, move to those in the east, then back to those in the west and then work back towards the east again. This is very common for those working asteroids for astrometry when getting two images of each asteroid and wanting a certain amount of time between images. Print This sends the current results set to a printer or a text file that can be manipulated in another program or printed. The ‘U’ column in the results table comes into play at this time. The ‘U’ column is the only editable field in the table. If the box is checked, then if the results are being sent directly to a printer, the given line is printed in bold type. If not checked, the line is still printed but in normal type. The ‘U’ setting has no effect if the results are sent to a text file. The default directory is \MPO\UDATA. The name of the file for an AltAz search is ALTAZ.TXT. The name of the file for a Photo search is PHOTO.TXT. 174 H/G Calculator The H and G Calculator allows you to compute the absolute magnitude (H) and phase slope parameter (G) for an asteroid. To do so, you must have calibrated (Johnson V) magnitudes taken over a sufficient range of phase angles. If you have data from only a limited range of phase angles, you can still compute the value of H by using an assumed value for G. The calculator uses the algorithm developed by Alan Harris for his FAZ program. For the best theoretical results, you should always use data from the maximum of the curve. If you use the average and the amplitude varies significantly during the apparition (amplitude often increases at higher phase angles) then you will not get the correct value for G. This is more a consideration for near-Earth asteroids since they can reach much higher phase angles than main-belt objects. Not only must the magnitudes be on a calibrated system, but they must be corrected to unity distance by applying a factor of –5*log(Rr) where R is the sun distance, in AU, at the time of the measurement and r is the earth distance. If you have the uncorrected, but still calibrated magnitude, for a given date, the calculator can compute the corrected magnitude for you. H/G Calculator – Data Input Mag Enter the calibrated magnitude for a given phase angle observation. This value must be corrected to unity distance. If you have only the uncorrected magnitude, use the “RM” button to calculate the corrected magnitude after you have entered the uncorrected magnitude into this field. RM Click this button displays the Reduced Magnitude form. This form converts the value in the Mag field to one corrected to "unity distance" and computes the phase angle for the asteroid at a specified time and date. If the computed values are accepted, they are automatically entered into the Mag and Phase fields. 175 Mag. Err. Enter the estimated error of the magnitude. This can be as simple as 1.0857/SNR or include more terms that include errors for the transforms, averaging of several observations, etc. If not certain, enter a reasonable estimate, e.g., 0.01-0.02mag. Phase Enter the phase angle of the asteroid at the UT date/time of the observation. The Reduced Magnitude form can calculate this value for you. Add Click this button to add the data in the three entry fields to the list. Del Click this button to delete the highlighted item in the list of observations. Clear Click this button to clear all entries from the list. Fixed G / G / Plot Fixed G / Pre-Post Opposition / Calc See “Calculating H/G” for the use of these controls and the Pre/Post opposition radio button. Save Plot Click this button to display a save file form. You can save the plot as a 1024 x 725 Window bitmap (BMP) or PNG file. Save Click this button to save the list of observations. A Save dialog appears, allowing you to specify the name and location of the file. The default location is \MPO\UDATA. All files are forced to have the extension HGD (H/G Data). H/G Calculator – Reduced Magnitude Form Obs Mag. This is the uncorrected magnitude, taken from the Mag field on the H/G Calculator. Date / UT The UT date and Time of the observation 176 Number The number of the asteroid. If you don't know the number, or it doesn't have a permanent number but can be looked up by name, click the speed button next to this field to display a form that allows you to find the number of the asteroid in the current copy of the MPCORB file. Load Click this button to display a form that lets you locate the asteroid under consideration. Click OK on the lookup form to have the number of the asteroid (artifically created if not officially numbered) entered into the Number field and the elements for the asteroid stored into memory. The Compute button (see below) is enabled. Click Cancel on the lookup form to reset the Number field to 0 and clear the asteroid elements from memory. The Compute button (see below) is disabled. Compute Computes the corrected (reduced) magnitude based on the information in the previous fields. The Sun and Earth distances are displayed in the status bar at the bottom. Red. Mag. The calculated reduced magnitude. This field can be modified but you should do so only if you know the calculated value to be wrong. Phase Ang. The phase angle of the asteroid based on the information in the previous fields. OK Click this button to close the form and have the reduced magnitude and phase angle automatically entered into the appropriate fields on the H/G Calculator. Cancel Click this button to close the form without modifying the Mag field on the H/G Calculator. H/G Calculator – Calculating H/G There are two ways to calculate values with the H/G Calculator Compute H and G Use this method when you have observations that span a large range of phase angles and, most important, where some of the observations were made at phase angles of <7°. As you can see from the screen shot of the H/G Calculator, the slope of the line changes significantly at small phase angles, i.e., near opposition and so showing the "opposition effect." If all the data is confined to a relatively small range of phase angles, one of which are near 10° or less, you should use the "Fixed G Value" method as well and then compare results. 177 Make sure the Fixed G box is not checked. If you are going to display a dual plot by checking the "Plot Fixed G" box (see below), then enter the fixed value for G in the “G” entry field. Click the Calc button. This displays the data points with a trend line on the plot and the computed values for H and G on the status bar at the bottom of the H/G Calculator. The two plots below show the difference between not checking or checking the “Plot Fixed G” box. If you do not check the box, then only a single set of lines (black) is displayed. The wider line is the phase curve itself for the given solution. The thinner lines represent the upper and lower bounds of the error envelope for the solution. If you do check the “Plot Fixed G” box, then a second set of lines is displayed in red. These show the phase curve and error envelope when the solution is forced to use the value of G in the entry field and an error of ± 0.2. The MPC uses a default value of G = 0.15 for its calculations of H when G is not known. This is a compromise value since the value of G has been shown to have a strong dependence on taxonomic class (or albedo). If you know the class of the asteroid, then enter an appropriate value for G to get a more realistic comparison between the phase curve found by the calculator and that expected for the given asteroid class. Compute H Using Fixed G Use this method when the observations do not cover a good range of phase angles or, even if they do, none of the observations are for phase angles <7°. If you have observations close to this value, try both methods and compare results. 1. Make sure the Fixed G box is checked. 2. Enter a default value for G. The Minor Planet Center uses 0.15 for the default value. You should use this as well, unless you have good reason to suspect another value. 3. Click the Calc button. This displays the data points with a single set of phase curve and error envelope lines on the plot. The computed value for H and the fixed value for G are displayed on the status bar at the bottom of the H/G Calculator. 178 Pre/Post Opposition Radio Buttons In rare cases, the value for G for an asteroid is not the same before and after opposition, mostly notably the opposition effect – the sudden brightening near opposition – is different on each side. The H-G calculator computes not only the phase angle but on which side of opposition the observation was made. The data can be filtered to include pre- and post-opposition data or just one or the other. The “Both” option plot both sides using red for pre-opposition data points and blue for post-opposition. If you select this option and all the points are one color, then you have no data on the other side of opposition. The “Combined” option plots all data points as black circles – it does not discriminate between pre- and postopposition. This is useful for publications that do not accept or handle color plots well. Show Errors Box As always, you should include errors in your results, be they in a table or in a plot. If you check the “Show Errors” box and then the “Calc” button, the calculator includes error bars on each data point. The errors may be so small that you cannot readily see the bars at full scale. As with the lightcurve plots in Canopus, you can zoom the plot (drag down to the right). The screen shot above shows the error bars for the upper left portion of the full plot, between 0 and 5 degrees phase angle. 179 180 Double Star Observations Canopus now includes enhanced features for measuring double stars. This includes easier setting of the reference position (the primary star) as well as recording the observations and being able to generate complete or summary reports. The summary reports can even reduce the saved raw instrumental magnitudes in different filters into standard magnitudes, greatly increasing the scientific value of your observations. 1. Use the Double Stars List to select all the images you want to measure. This List is easier than having to use the Image | Open and locating the next file after each measurement. 2. For each image, specify the reference (primary) star, specify the secondary star, and then add the information to the DoubleStarsManagement table in MPO\COMMON. 3. After all images have been measured, use the Double Stars Measurements form to review the data and generate a report of the raw information for all data or that matching a name and/or date range, or a summary report that can combine observations of a given star/filter/date into a single observation with errors and reduced standard magnitudes. How Double Stars Are Measured When you do an AutoMeasure for an image, this generates a set of "plate constants" that allow converting an X/Y position to RA/Declination. Canopus stores the measured RA/Declination for the primary and secondary and then computes the distance and position angle using standard formulae found in "Astronomical Algorithms" by Meeus and "Observing and Measuring Visual Double Stars" by Argyle. This is a more rigorous method than simply computing the X/Y positions and applying plate scales (arcsec/pixel) to find the distance since it also accounts for the cos(Declination) factor in the RA and positions near the pole. Users Guide The Users Guide contains a detailed tutorial on measuring double stars in the “Supplemental” chapter. This section provides additional information as needed. Adding Double Stars Data The Double Stars Input form (see step #9) in the previous section displays the information recorded by Canopus. Some of the data can changed but most cannot. JD (read only) This is the Julian Date of mid-exposure as determined by reading the image FITS/SBIG header. 181 UT (read only) The calendar date and time (UT) corresponding to the Julian Date above. It is not corrected for heliocentric JD. Name Enter the name of the primary. This is usually the WDS catalog entry for this double star. This field cannot be blank. Filter Select the filter used for the observation. The options are the Johnson-Cousins photometry filters, excluding U, i.e., BVRIC(lear). Primary Data RA (read only) The measured RA of the primary star after doing an image match and finding the plate constants for the image. Dec (read only) The measured Declination of the primary star after doing an image match and finding the plate constants for the image. Mag (read only) The instrumental magnitude of the primary star AM (read only) The air mass of the field based on the measured RA/Dec of the primary star, the configuration settings for longitude and latitude and the corrections for image mid-exposure. This information is used in the summary reports when applying PhotoRed transforms and first-order extinction values. Secondary Data RA (read only) The measured RA of the secondary star after doing an image match and finding the plate constants for the image. Dec (read only) The measured Declination of the secondary star after doing an image match and finding the plate constants for the image. Mag (read only) The instrumental magnitude of the secondary star Dist (read only) The computed distance of the secondary from the primary using the measured RA/Dec of each star. PA (read only) The position angle of the secondary from the primary, with 0° being North, 90° being East, etc. The value is computed using the measured RA/Declination of the two stars. Load DS List Image Check this box to have Canopus automatically load the next image in the Double Stars List when you click OK (or press Enter since the OK button is the default control). If this box is not checked, you must manually load the next image using the Load button on the Double Stars List form or using Image | Open from the Canopus main menu. This checkbox is disabled if the Double Stars List form is not open. In most circumstances, you want this box checked, which is the default, when using the Double Stars List. The exception would be when you have a multiple star on a set of images, e.g., an AB, AC, and BC pair. In this case, uncheck the box so that when you add a measurement, the current image remains loaded with its astrometric solution still valid. For example, if you set the A star as the reference and measured the B as the secondary, you can then measure the C component as the secondary without having to reset the A as the reference. Just be sure to change the entry in the Name field to match which pair is being measured. For the B-C pair, you would have to reset the B star as the reference and the C as the secondary. 182 One you move to a new set of images with just a primary-secondary pair, check the box so that Canopus automatically loads the next image in the Double Stars List. OK Click this button to add the data to the DoubleStarMeasurement table. A confirmation beep is played if the data is added to the table. Use the Double Star Measurements form to review the data and generate observation reports. If the Double Stars List is open, then clicking OK (and then OK on the confirmation message) on this form sends a message to the Double Stars List so that the next image in the list is automatically loaded and measured, i.e., it's as if you immediately clicked the Load button on the Double Stars List form. See the discussion above under "Load DS List Image." Cancel Click this button to close the form without adding the data to the DoubleStarMeasurements table. The Double Star Measurements Form The Double Star Measurements form displays all observations that you've recorded using the Save Dist/PA Data item on the Image popup menu and displayed in the Double Stars Input form. With this form, you can delete records but not add new records. You can edit some of the data "in situ" for a given record. This form has a minimum size to assure that all controls remain visible. However, it can be expanded to make viewing the report easier. The previous size and position of the form are restored each time the form is opened. This section describes the data and basic operation of the form. See “Generating Double Star Reports” below for details on creating reports based on the data filters and other settings on the form. Data Table Displays the principal data for each observation. Additional data is recorded and included when a report is generated. The data in four columns can be edited Use If checked, the observation is included in the summary reports. All observations are always included in the Full report. Primary The name for the double pair. As seen in the screen shot above, the name can be used to indicate specific pairs in a multiple star system. A maximum of 20 characters is allowed. Filter When the cell is active, a drop down list can be used to set the filter. AM The air mass for the observation. If the configuration settings for longitude, latitude, and for computing mid exposure were not correct when adding the data initially, this can be corrected by setting the configuration correctly and then clicking the Air Mass button. This computes the air mass for all observations, not just those Sort by Select the order by which the observations are sorted. The options are 183 RA Name (primary) Julian Date Search Enter the initial or complete text for which to search records, based on the current sort order. When sorting by JD, you must enter the Julian Date, not the calendar date and time. Define Filter Select one of the radio group items to filter the data by name and/or date. Only that data included with a filter is included in a report. None All records are displayed/included Name Include only those records where the name of the primary matches the entry in "Name" exactly. The filter is case-sensitive and does not include partial matches. For example: if you enter "Test", then "Test 1" would not be included since it's not an exact match, nor would TEST since it's upper case while the filter is mixed upper/lower case. Date Includes only those records between the start and end dates, inclusive. To include only one date, set Start and End to the same calendar date. The drop-down lists display a calendar that lets you pick the date or you can enter it in the field directly. The End Date must be equal to or greater than the Start Date. Name/Date Includes only those records that mach the Name and Date range. Active Check this box to invoked the filter (not available if None is selected). Uncheck the box to remove the filter, which has the effect of selecting None but leaves the box enabled so you can use the filter again without redefining it. If you change the entry in Name or the two date range controls, the Active box is automatically unchecked, i.e., the filter is no longer applied. This forces a check of the new filter parameters, which is done every time the Active box is checked. Report Click this button to generate a report based on the current filter and sort order. Full Includes all raw data for all stars within the data filter, even those with the Use flag not checked. Summary (PR) Creates a summary report within the data filter that reduces the instrumental magnitudes to standard magnitudes based on transforms and first order extinction values found in PhotoRed. Summary (Fixed) Creates a summary report within the data filter that applies a fixed value to all instrumental magnitudes. This value can be determined from methods in PhotoRed or other means. The report can be generated only one filter at a time since the offset between instrumental and standard magnitudes is likely different for each filter. CI The color index used for a Summary (PR) report. This group is disabled if the report type is Full or Summary (Fixed). In the latter case, the CI method is forced to "None". Obs Check the boxes for those filters for which you have observations and want to be included in the summary report. If using the Summary (PR) report, you must include the filters used for the selected color index (if not NONE). 184 Astrom Check those boxes for those filters for which you want the observations used to determine the distance and position angle of the secondary star. If you select a filter in this group, then it must also be selected in the Obs group. For faint stars, where the SNR is not as high, you may want to use only Clear observations for astrometry. Obs Enter the initials of the observer for the stars included in the report. Usually this is two letters - the first/last name initials. In some cases, a three-letter code may be assigned by the USNO and that would be entered instead. A maximum of five characters is allowed. Offset Enter a fixed offset to be applied to all raw instrumental magnitudes in the Summary (Fixed) report. Using this approach assumes no corrections for color index or extinction. Report Click this button to generate the selected report. Double Stars – Generating A Report The Double Star Measurements form allows generating one of three types of reports. Fixed Report This shows the raw data for all observations matching the data filters (if any). Otherwise, the other options to filter data, e.g., the Obs and Astrom filter settings are ignored. Summary (PR) This report uses the data filters of name and/or date along with the settings in the CI (color index), Obs and Astrom group settings. Transforms and first order extinction values found in PhotoRed are applied to the raw instrumental magnitudes to produce standard magnitudes included in the report. See below for how data is summarized. Summary (Fixed) This report uses the data filters of name and/or date, the fixed offset value in "Off.", and the Obs and Astrom group settings. The fixed offset is applied to the raw instrumental magnitudes to generate a standard magnitude. This does not include transforms or first order extinction corrections. See below for how data is summarized. The two summary reports should provide all the information needed for publication, included errors (standard deviations) and the values used to reduce to standard magnitudes. Define Filters All reports honor the settings within the Define Filter group. Select an option in “Define Filter”. 2. None Includes all records Name Includes those records matching the value in the “Name” field. The filter is case-sensitive, i.e., 'AG' and 'ag' are not the same Also, the match must be exact, i.e,. you cannot use partial matches, e.g., all stars starting with 'AG' Date Enter the start and end calendar dates. The Start date must be equal to or before the End date. The dates are for midnight on the specified date, so to include observations made after midnight, set the End date to one day later. For example, if you made measurements on Feb. 14, 2006 at 07:00 UT, you should set the End date to Feb. 15, 2006. Name/Date Combines the Name and Date filters, meaning you could specify all observations for a given star during a given month or year. Check the Active check box to see the results of the filter settings. The report is somewhat WYSIWYG, meaning only those records that appear in the data table when you click the Report button will be considered for inclusion in the report. 185 Remember that the USE flag is ignored for the Full report, which includes a column to show if the USE flag is checked or not. The summary reports consider only those records where the USE flag is checked. How a Summary Report is Generated When running a summary report, two initial steps are always taken 1. Load the data for all observations for which the USE box is checked and are within the data filters of name and/or date range. 2. Sort the data by Name and JulianDate in ascending order, i.e., in the case of observations with the same primary name, the "tie-breaker" is the Julian Date. In the following, “each observation” means that the primary and secondary are handled independently. 3. Iterate through the records. 1. Find the first record for a given name. The associated JD is the "base value" for group. All observations with the same name and having a JD within 0.5d of the base value are placed into the same group for summarizing observations. 2. All observations within the name/JD group are placed into subgroups based on the filters selected in the Obs group. A separate tabulation is kept for all observations within the name/JD group that match the Astrom filter settings. 3. If the report type is Summary (PR), a check is made to see that there is a least one observation in each of the filters indicated by the CI selection (unless the selection is NONE, in which case the test is forced to succeed). 4. If the test succeeds, the color index is computed: If Summary (PR) and the color index setting is not NONE, the mean instrumental values are computed for the two required filters and corrected for first order extinction. The difference between the instrumental magnitudes is then corrected to a standard color index, e.g,. b-v to B-V using values read from PhotoRed's Transforms data. If Summary (Fixed), the color index is set to 0.0. This allows the same basic formula to be applied to the raw instrumental magnitudes regardless of the summary report type. 5. The mean instrumental magnitude and standard deviation for each subgroup of observations based on filter is computed. 6. The first order extinction values are applied to the mean instrumental values and then corrected to standard magnitudes using the color index found in step 4 and the transforms values from PhotoRed. 7. The summary data is written for each observation. 4. After all the records have been processed, the mean and standard deviations of the distance and position angle values that were maintained independently of the instrumental magnitude reductions are found. This data is added to the summary line for the given primary/secondary pair. Since the distance and position angle are maintained independently, the values are duplicated for each name/JD summary line, regardless of filter, i.e., the distance and separations are not maintained no reported by filter but all specified observations are "lumped" into a single data set. Generating a Fixed Report See Generating a Report for a discussion on how reports are generated and setting the options in the “Define Filter” section. Steps for Generating a Full Report Set the options in the “Define Filter” section as desired. 186 Select “Full” for the report type. This forces the CI group to be disabled and set to "NONE". Select the filters in the Obs group for which you want to include the observations. For example, in the screen shot above, only those observations made with the C filter will be included. You can select more filters than you select in the Astrom group. Select the filters in the Astrom group for which you want the observations to be used to calculate the distance and position angle of the double star. For each filter selected here, you must have the same filter selected in the Obs group. Set the Obs field with the initials of the observer who made the measurements. If more than one person, generate a separate report for each observer. Click the report button. Once the report is generated (assuming at least one observation is found), the form switches to the Report page to display the report. The report can be edited, but use caution to save the formatting of the lines. Save Click this button to save any changes you make to the report. A file save dialog appears where you can choose to save the file under the same or different name. The file is saved and then the report is reloaded to confirm that the changes were recorded. Generating a Summary (PR) Report See Generating a Report for a discussion on how reports are generated and setting the options in the "Define Filter" section. Steps for Generating a Summary (PR) Report Confirm the settings in the PhotoRed Transforms form for: First Order Extinction for each filter to be included in the Obs group selection 187 Color Index for two filters to be included in the Obs group selection (if the CI group is not set to NONE). These must be either B and V, V and R, or V and I. Transforms (slope and zero point) for each filter to be included in the Obs group selection The "Hidden" transforms for the color index selected in the CI group. These convert instrumental magnitude color indices to standard magnitudes indices. The Transforms values must have been determined using the same color index that you select in the CI group below. Set the options in the "Define Filter" section as desired. Select "Summary (PR)" for the report type. Select the CI filter combination. If NONE, the color index corrections values are forced to 0.0 (no correction). However, the transforms and first order corrections will still be applied. Select the filters in the Obs group for which you want to include the observations. For example, in the screen shot above, observations made with the V, R, and C filters will be included. The first two are required since the V-R color index was selected. You can select more filters than you select in the Astrom group. Select the filters in the Astrom group for which you want the observations to be used to calculate the distance and position angle of the double star. For each filter selected here, you must have the same filter selected in the Obs group. Set the Obs field with the initials of the observer who made the measurements. If more than one person, generate a separate report for each observer. Click the report button. Once the report is generated (assuming at least one observation is found), the form switches to the Report page to display the report. See Double Stars - Summary (Fixed) Report for a sample of the report. Generating a Summary (Fixed) Report See Generating Reports for a discussion on how reports are generated and setting the options in the "Define Filter" section. Steps for Generating a Summary (PR) Report Set the options in the "Define Filter" section as desired. Select "Summary (Fixed)" for the report type. This forces the CI group to NONE and disables it. Select the one and only one filter in the Obs group for which you want to include the observations. For example, in the screen shot above, observations made with the C filters will be included. You must run a separate report for each filter since the value in the "Off" field is very likely different for each filter. 188 Select the same filter in the Astrom group that you selected in the Obs group. Set the Obs field with the initials of the observer who made the measurements. If more than one person, generate a separate report for each observer. Enter the offset value to be applied to the raw instrumental magnitudes. This should always be 0.0 or a positive number. If you enter 0.0, the raw instrumental magnitudes are reported. A typical value for the V filter is in the range of 20.0-23.0. This value can be determined by using the first step of the Binzel Method in PhotoRed, where you measure a field and find the average of the differences between the instrumental magnitude and the standard magnitude for a number of reference stars. Click the report button. Once the report is generated (assuming at least one observation is found), the form switches to the Report page to display the report. Note the second line of the report. This indicates the color index correction values that were applied. In a FIXED report, the slope is always 0 and the Offset is the value. The third line contains the First Order extinction values from PhotoRed. The fourth line contains the Transforms that convert instrumental magnitudes to a standard filter. The first value for each filter is the color index dependency while the second is the zero point offset. In the case of the Summary (PR) report, the Transforms values must have been determined using the same color index that you selected in the CI group. The report is sorted first by name, then date, then filter. In the example above, all observations were made using the same filter. There are more columns than appear in the screen shot above. They are: Primary Data Columns Name Name of the double star pair assigned when adding data using the Double Star Input form. RA/Dec The approximate J2000 position of the primary star in the pair. Fil The filter used Mags The reduced magnitudes, unless FIXED and Offset = 0.0. In that case, the raw instrumental magnitudes are reported. PA The average position angle Sep The average distance, in arcseconds. Epoch The Julian Epoch, rounded to the nearest 0.001yr (0.36525d) NA The number of observations used to find the average for the distance and position angle values. 189 NF The number of observations used to find the average instrumental magnitude in the given filter. Obs The observer entered in the Obs field on the Data page CIP The reduced color index of the primary CIS The reduced color index of the secondary Errors Columns PSD The standard deviation of the position angle, in degrees DSD The standard deviation of the separation, in arcseconds CIPSD The standard deviation of the primary's color index as computed by averaging the raw instrumental magnitudes in the appropriate filters. CISSD The standard deviation of the secondary's color index as computed by averaging the raw instrumental magnitudes in the appropriate filters. MPSD The standard deviation of the primary's reduced magnitude. MSSD The standard deviation of the secondary's reduced magnitude. 190 JD Calculator The Julian Date (JD) Calculator converts local (computer clock) date/time to Julian Date, Heliocentric Julian Date, and Universal Date/Time. It also goes the opposite direction, converting a Julian Date to both Universal and Local Date/Time. Date/Time Fields The date field formats follow your international settings in Windows, with the exception that years are forced to four digits. The time fields are forced to 24-hour format with leading zeros required and seconds included. For example, 2:00 AM is entered as 02:00:00 and 1:07:08 PM is entered as 13:07:08. Real Time Clock If the "Run Real Time" box is checked, all controls in the Calculate JD group are disabled and the fields in that group automatically update once a second. Julian Dates The Julian Dates are always based on Universal Time. Calculate JD Group UTOffset Enter the hours and minutes difference between your computer clock and Universal Time. This is not necessarily the same as the difference based on your time zone. For example, if your computer clock is set to UT, you would enter 00:00. This setting is saved each time you close the form, but it does not automatically update when your computer clock shifts to or from Daylight Saving Time. Behind Check this box if your time zone is west of UT, e.g., anywhere in the contiguous United States. Calculate JD - Local Date/Time Enter the local date and time to calculate the current JD, HJD, and UT date/time. RA/Dec Enter the approximate RA (hh:mm - leading zeros required) and Declination (to nearest degree) to have the Heliocentric JD calculated. The HJD is the time light from a distant source reaches the sun, not the earth. This value is used in variable star work to put all data on a common zero point. 191 UT JD/JHJD/UT Date/UT Time These fields are read-only. As long as the group is not disabled (see "Real Time Clock"), you can copy the value from these four fields (right click over a given control) to paste into another program. Calculate UT Group UT JD Enter the Julian Date for a given Universal Date/Time to have the calculator compute the UT and Local Date/Time corresponding to that JD. UT Date/UT Time/Local Date/Local Time These fields are read-only. You can copy the value from these four fields (right click over a given control) to paste into another program. 192 Lightcurve Ephemeris As you work an asteroid or maybe variable star where you cannot get data for an entire cycle in one night, your lightcurve may have gaps in it. If those gaps are a significant portion of the curve or if they happen to be at minimum and maximum, the Fourier period analysis is handicapped to one degree or another since it has to guess how to fill in those gaps in just the right way. The solution is, of course, “More Data!” but it would help if you need when to observe so that you were getting data to fill in the gaps and not just overlapping existing parts of the curve. That is the purpose of the Lightcurve Ephemeris utility. Users Guide The Users Guide contains a full tutorial on using this utility. This following sections provide additional information and details on the input fields. Generating an Ephemeris Lightcurve If you have a data file available, it’s simple to generate a curve for a given date and compare that curve to the one you have from available data and see when you would have to observe on that date to catch the part of the curve that’s missing data. Load Data Click this button to display a file open form where you select the data file with the Fourier values for the target of interest. Period This entry field is automatically filled-in when you load the data file. It is a read-only field and so cannot be edited. The value is in days. TO This is the Julian Date zero-point of the data and is filled-in automatically when you load the Fourier data. It is not the JD for the earliest data point but corresponds to about the middle of the data set. This is a read-only field and cannot be edited. Avg This is the average magnitude of the data and is automatically filled-in when you load the Fourier data. It is a readonly field and cannot be edited. Name Enter the name of the object. This appears in the title of the generated plot. 193 Start Enter the date for which you want to generate the ephemeris curve. The format follows your Windows settings except that you must enter all four digits of the year, e.g., mm/dd/yyyy for a typical US entry, dd/mm/yyyy for many other countries, and yyyy/mm/dd for ANSI date settings. Use leading zeros if necessary for months and dates. UT Enter the start time for the ephemeris for the given date. The format is 24-hour time in hh:mm format. Use leading zeros if necessary for hours and minutes. Days Enter the total number of days covered by the ephemeris. A good selection is one that covers from two to four cycles if the period is < 0.5 days. The longer the period, the larger the interval you’ll need to enter to cover at least one cycle. Generate Click this button to generate the ephemeris curve plot. Print Click this button to display a file save dialog. You can save the plot as a standard Windows 24-bit BMP or compressed, nearly lossless PNG file. The default directory the first time you save after opening the form is \MPO\CANOPUS. 194 Star Profile After you load an image, you can view the profile of the star. This is a plot that shows the total flux within a given radius versus radius. 1. Load an image 2. Select Utilities | Star profile from the Canopus main menu. This displays the profile form. The form remains on top so that you can click on any star and check its profile. The profiles for every start should be similar in shape. A significant change may indicate a close companion, an unexpected hot or cold pixel, or something else entirely. The form shows only one profile at a time, that of the X-axis (left to right) or Y-axis (top to bottom). Use the profile radio button to select which profile to view. These, too, should be similar. If not, one cause would be trailing during the exposure. The status bar at the bottom shows to values. Max The ADU of the “hottest” pixel in the profile. 0-Width The width, in pixels, of the profile. The cut-off is when the pixel values are less than one-sigma above the sky background. What surprises many people is that, when using a sufficiently large aperture to measure a bright star and using that same aperture on a fainter star, the 0-width of the two stars is very similar. Actually, they are the same but the one-sigma cut-off will show a slightly larger profile for a brighter star. The size of the star on the image is almost completely a function of the optics alone. Brighter stars appear larger because more of the outer wings of the profile are still above the sky background and so can be seen and measured. For a fainter star, the wings are still there, but they are below the threshold of detection, either by eye (most cases) or by the software (when near the sky background). 195 196 Image Processing Canopus offers image manipulation essential to basic astrometry and photometry. This includes scaling, creating master darks, flats, and bias frames and then merging them with raw images. Other options include stack and average, add/subtract/multiply/divide, and resampling, adding WCS data after an AutoMatch, and others. Scaling Images The Image Scaling form works with the images loaded on the Measure or Blink pages of the main form. To display the scaling form, right-click over an image and select “Image scaling” from the popup menu; or select “Image | Scaling” from the Canopus or PhotoRed main menu. Many of the scaling algorithms are based on those appearing in The Handbook of Astronomical Image Processing by Berry and Burnell. See that excellent book for details on the scaling algorithms implemented here, and many other things. Scaling when using this form affects the displayed image only. The original pixels are not altered and so the accuracy of astrometry and photometry is not affected. You can copy the altered displayed image to the Windows clipboard for pasting into a graphics or other program. Using the Scaling Form In general, you will select a scaling mode and then change settings that apply to that mode. You will be able to set the changes on the current image in real time. Invert Check this box to invert the image from its current state, e.g., to go from white stars and black sky to black stars and white sky. Preview Click this button to force the image to be updated using the current scaling settings. Reset Click this button to reset the image to the current default scaling mode. You can change the default with this form. 197 Make Default Make the current scaling settings (mode, and settings) the default for all images to be loaded afterwards. This works only if the subsequent images all have about the same range and background. For example, if using standard deviation normal and a very bright star appears, it will overpower the scaling and you will not see faint stars. Restore Default Click this button to reset the default scaling to standard deviation, normal. Slider Bars The two slider bars, “Black” and “White”, control the range of values within a given scaling mode. The Black slider sets the pixel value below which all pixels are pure black while the White slider bar sets the pixel value above which all pixels are white. The range of values for the sliders is always 16-bit based, 0 to 65535, even when working with 32- and 64-bit images. They still work with these images effectively. The slider bars are active but have no effect when using the standard deviation scaling mode. Mode Sliders Description Standard Deviation No The Canopus default is to use the “Normal” setting of this scaling mode. “Normal” usually gives a pleasing presentation of an image. However, it can be fooled by a very bright star such that faint stars are hidden. “Compressed” results in a much brighter background but this allows seeing very faint stars. You can set the high and low values for the two submodes independently using the spinner/edit fields in that section. Bright/Contrast Yes This is akin to the brightness and contrast controls on your monitor. When you select this mode, the range of the slider bars changes to 0 to 100 and both are set to a default of 50. Stretch Yes Assuming 16-bit data, this forces that data into a range between the black and white slider bar values in effect, reducing the number of possible pixel values to display on the screen. Gamma Yes Gamma scaling provides control over mid-range values while the high and low ends remain mostly unchanged. The Gamma entry field is enabled. Values must be between the range of 0 and 1. Log scaling compresses a large dynamic range into a smaller range based on the logarithm of values, not a linear-fit as does the Stretch scaling. Log Gamma/Log Yes Yes The Gamma entry field is enabled. This is a power value, i.e., X = 10X, so very small changes in Gamma result in very large changes to the general scaling. This combines the Gamma and Log scaling functions. This is particularly good for viewing images of galaxies, where bright centers can overwhelm faint details in the arms. The Gamma entry field is enabled. A good starting value is 0.2-0.3. Biases, Darks, and Flats All pixels in a CCD are not created equal, they vary in response not only from pixel to pixel but even within a single pixel. The chips are not at absolute zero, so there is thermal noise to one degree or another. These inequalities and 198 noise influence the value generated by photons when the CCD chip converts them to electrons. Bias and dark frames along with flat fields are used to remove as much of these errors as possible so that what’s left is “pure” data. Bias Frames Bias frames are 0-length exposure dark frames. These are required when using darks that are scaled down to match the light frame exposure. If you are using a dark of the same exposure as the light frame, a bias frame is not required. However, including it should the dark and light have the same exposure does no harm since the dark is scaled 1:1. To create a Master Bias Frame, use the same steps as for a Master Dark, except that you use an exposure of 0. If your camera does not allow 0-length exposures, use the shortest exposure it does allow. Dark Frames Dark frames are pictures of the natural noise in the camera at a given temperature and length of exposure and are usually created by taking a series of images without opening the shutter and then averaging the several images to create a “master dark.” The data from this image is subtracted from a "light" image taken with a CCD camera, thus subtracting out the noise and leaving the "real" data. Scaled Darks It is possible to use dark frames that have a different (longer) exposure than the light frames. It is also possible to use darks taken at a different temperature but the MPO Software does not support this option. When using a dark of a different exposure, you must also include a bias frame in the processing, which is used to subtract out the "base" dark current from both the dark and light frame, leaving only (to first approximation) the thermal noise dependent on temperature. If using a master dark with the intent of applying it to light exposures of different lengths, the master dark cannot include the bias frame subtraction. If it did, then Canopus would try to subtract the bias frame again and produce very strange results. Flat Fields Flat fields are pictures that reflect the sensitivity of each pixel on the chip. There are several techniques for producing these images. See the “Observing Guides” page on the MPO web site for one set of instructions from Stan Moore, a noted CCD imager (http://www.minorplanetobserver.com/htms/obsguides.htm). When a flat is available, the data from the flat is used to multiply (or divide) the value for each pixel in the light image such that, had the light image been of a perfectly and evenly illuminated white card, all pixel values would be the same. In other words, the flat field adjusts for the fact that not all pixels on the CCD chip have the same sensitivity, for vignetting, and even dust spots. General Requirements The scope of proper generation and use of darks and flats is beyond this manual. You should consult texts on the subject and get advice from experienced observers. 1. Bias, dark, and flat images must be the same size as the light image, i.e., the same number of pixels along the horizontal and vertical axes. The bias and dark must also be the same bit size, meaning that you cannot combine a 16-bit integer dark with a 32-bit floating point light image. The flat is normalized, if necessary, to values centered about 1.0, so it can be of a different bit depth. 2. The files do not have to be of the same type, e.g., the dark can be a FITS and the light an SBIG but neither can be a JPEG or BMP since the program must be able to read the header information, which is available only in FITS/SBIG images. 199 3. The Dark must be taken at the same temperature as the light. It can be a different exposure if a bias frame is also used. Canopus does not enforce the temperature rule but ignoring it can result in terrible looking images and poor astrometry or photometry. 4. The Flat field can be normalized (median value = 1) or non-normalized (raw pixel values). Canopus normalizes flats as needed. The flat should have been created using a dark frame, i.e., the natural noise removed, before being applied to light images. Working with Bias Frames This is required only if using darks with a different exposure as the light frame. 1. To load a bias frame, select “File | Load Bias”. This displays a file open dialog. 2. Select the desired file and click OK. This automatically checks the “File | Use” menu in the bias frame section. 3. If you want to temporarily disable using the bias without removing it from memory, select the menu option again so that it is not checked. The bias is kept in memory but is not subtracted from any image loaded thereafter until the option is again selected. If the menu item is grayed, this means that a bias frame has not been loaded. Select “File | Clear Bias” to remove the bias frame from memory. This also disables the Use menu item. Working with Dark Frames 1. To load a dark frame, select “File | Load Dark”. This displays a file open dialog. 2. Select the desired file and click OK. This automatically checks the “File | Use” menu in the dark frame section. 3. If you want to temporarily disable using the dark without removing it from memory, select the menu option again so that it is not checked. The dark is kept in memory but is not subtracted from any image loaded thereafter until the option is again selected. If the menu item is grayed, this means that a dark has not been loaded. Select “File | Clear Dark” to remove the dark frame from memory. This also disables the Use menu item. Working with Flat Fields 1. To load a flat field, select “File | Load Flat”. This displays a file open dialog. 2. Select the desired file and click OK. This automatically checks the “File | Use” menu in the flat field section. 3. If you want to temporarily disable using the flat without removing it from memory, select the menu option again so that it is not checked. The flat is kept in memory but is not applied to any image loaded thereafter until the option is again selected. If the menu item is grayed (disabled) that means a flat has not been loaded into memory. Select “File | Clear Flat” to remove the flat field from memory. This also disables the Use menu item. Image Processing - Creating a Master Dark In general, you should take at least four to sixteen raw darks at the same temperature, exposure, and binning as the images to which you will apply the master dark. 1. Shoot the raw darks. 2. Use the Average or Median method in the Batch Processing form to create a single image. Median is often preferred to remove excessively hot pixels due to cosmic ray hits. 200 When creating a master flat or dark, all images must be in FITS format and have the same number of rows and columns. Any image that has a different number of rows or columns from the first image that is processed is ignored. Image Processing - Creating a Master Flat There are many methods for obtaining the raw images used to create master flat. Twilight flats, all-sky flats, light box flats, and T-shirt or dome flats all have their advocates. In general, you should take between four and sixteen raw images. Remember to take a series for each filter, as you must create a separate flat for each filter. You must also take a number of dark frames using the same temperature and exposure as the flats. These “flat darks” are combined to create a master dark frame to be subtracted from each submaster flat to create the final master flat. 1. Take the raw flats through each filter. 2. Take the raw darks, making sure to use the same temperature and exposure time as the flats. 3. Using the Average or Median method in the Batch Processing form, create a master flat dark from the images taken in step 2. Median is often preferred as it helps eliminate hot pixels due to cosmic ray hits. 4. Use the Merge Dark method in the Batch Processing form to create submaster flats by subtracting the master flat dark from each of the raw flats taken in step 1. 5. Use the Median method in the Batch Processing form to combine the submaster flats to create a single master flat. When creating a master flat or dark, all images must be in FITS format and have the same number of rows and columns. Any image that has a different number of rows or columns from the first image that is processed is ignored. Image Processing - Converting Images Canopus allows you to convert images from one format to another, with some limitations. FITS images can be converted to SBIG, Windows BMP, or JPEG formats. SBIG images can be converted to FITS, Windows BMP, or JPEG formats. Windows BMP and JPEG images cannot be converted to another format. The image conversion menu is located under Utilities | Image Processing on the main menu. Converting FITS Images to SBIG Format The native image format for files taken with MPO Connections is FITS. This is a universal standard that is read by most programs. However, some programs do not read the FITS format but do read the SBIG format. Canopus provides this feature to allow opening the images saved by MPO Connections in those programs with image manipulation capabilities that cannot read the FITS format. There is information stored in the SBIG header that is not available in the FITS header. Some of the information can be “faked” by going to the Configuration form and setting the following fields to match the values you want entered in the SBIG header: Observer, Focal Length Horizontal Pixel Size Vertical Pixel Size Select Image | Convert FITS to SBIG from the main menu. In the file dialog that appears, select one or more files to be converted. Only FITS files can be opened. Click the Open button on the file dialog to start the conversion process. All files will have the same name as the original except that the extension is changed to SBIG. For example, A124.FIT becomes A124.SBIG. 201 The Background and Range values are determined using the default scaling in Canopus, i.e., based on standard deviation of the mean value. You will very likely have to work with the Background and Range values some before you’re able to see an acceptable display of the image in the other programs. This is no different from using the Scaling box in Canopus. Converting SBIG Images to FITS Format The native image format for files taken with MPO Connections is FITS. This is a universal standard that is read by most programs. The AutoMeasure feature of Canopus works only with FITS files. Some camera control programs do not create FITS images. This feature allows you to convert SBIG format images to the FITS format so that you can take advantage of the AutoMeasure routine in Canopus. There is information stored in the SBIG header that is not readily converted to the FITS header keywords. Some of the information can be “faked” by going to the Configuration form and setting the following fields to match the values you want entered in the FITS header: Observer, Focal Length Horizontal Pixel Size Vertical Pixel Size When converting the date and time in the SBIG header to the FITS header, the original time and date are maintained for the DATE and TIME FITS keywords. However, the UT, TIME-OBS, TIME-UT, and DATE-OBS fields are converted to Universal Date and Time based on the following: The date and time in the SBIG header are for the start of the image. The conversion from the date and time in the SBIG header to FITS header is based on the Configuration | Observer settings for Time Zone and Daylight Savings Time. For example, if the date and time in the SBIG header are Mountain Standard Time, then the Configuration | Observer settings must be set to MST, the UT Offset to 07:00:00, and the “Behind UT” checkbox must be checked. Select Image | Convert SBIG to FITS from the main menu. In the file dialog that appears, select one or more files to be converted. Only SBIG files can be opened. Click the Open button on the file dialog to start the conversion process. Since some programs save SBIG images with “unusual names”, e.g., 0700.0325.0001, the file filter allows you to select All files (*.*). Make sure the files you pick are actually SBIG files. All files are named using the full name up to the part at the last period and beyond plus a sequential number followed by the FIT extension with the exception that all periods in the file name save the last are converted to underscores. For example, 0700.0325.0001 would become 0700_0325_001.FIT, i.e., only one period is allowed in the file name that being the one that separates the file name from the FIT extension. 202 Batch Image Processing The Batch Image Processing form (the Batch form) can be used to process one or more raw images to create new images. The original raw image is never altered. Instead, a new image is created and saved. Naturally, you can process a processed image. For example, you might average several frames to create a single submaster and then median combine those submasters to create a final master. Dark Enter the complete path name to the master dark that is to be subtracted from selected raw images. Use the speed button immediately to the right of the entry field to use a file selection form to find and enter the file. Flat Enter the complete path name to the master flat that is to be median combined with selected raw images. Use the speed button immediately to the right of the entry field to use a file selection form to find and enter the file. Operator Enter the name of the operator image to be applied to selected raw images. This field is not always used. Save in original directory Check this box to make the default directory for the output image the same as the raw images. You can change the directory if the result is a single file and you are presented with a file save dialog. Uncheck the box to make the default for multiple image a different directly. Enter a valid path in the “Save to” field or use the speed button next to the field to locate or create a valid output directory. Keep original file name Check this box to have an output file replace an existing file. This is the case if you are processing a set of images more than once. For example, you would use Merge Dark to subtract the bias frame (as the Dark field) and then process those modified images to subtract the dark, changing the file to be used for subtraction. Make sure that you really want to overwrite an existing file. It’s always a good idea to make backups before doing any batch processing and to have the Canopus generate new files instead of overwriting originals. 203 This table describes the batch processing functions available in the Batch form. Action Description Uses Image Merge Dark Subtracts the Dark frame from one or more images. Can also be used to subtract bias frame from one or more images. Dark Merge Flat Median combines the Flat frame with one or more images. Flat Merge Dark and Flat Subtracts the Dark frame and then median combines the Flat frame with one or more images. Dark & Flat Average Averages the pixel values at each X/Y position in all the selected images to create a single value placed in the new image. No registration is performed. None (or Bias) Good for making master darks and/or flats. Median Median combines the pixel values at each X/Y position in all the selected images to create a single value placed in the new image. No registration is performed. None Good for making master darks and flats. Median Normalized Finds average value of center region of first image to create a scaling factor. All images are multiplied by this factor so that the centers of all the images have approximately the same average. This accounts for fading/brightening sky when getting sky flats. None After scaling is done, then median combine as described above is performed. No registration is performed. Good for making master darks and flats. Particularly good when making sky flats that have stars. Add Operator Adds the pixel value at X/Y in the operator image to the one at the same X/Y in each selected image. No registration is performed. Operator Subtract Operator Subtracts the pixel value at X/Y in the operator image from the one at the same X/Y in each selected image. No registration is performed. Operator Multiply by Operator Multiplies the pixel values at X/Y in the operator and selected image to create a new pixel value. No registration is performed. Operator Divide by Operator Divides the pixel value at X/Y in the selected image by the value at the same X/Y in the operator image. No registration is performed. Operator Merge with Operator Adds the pixel value at X/Y in the operator to that of the value in the selected image at the same X/Y. The value for each can be scaled, giving more weight to one image or the other. In video terms, a “partially dissolved” image is created. No registration is performed. Operator Stack (Average) The same as Average except that all images are registered. Greatly increases SNR while cutting down noise. The Operator image is the reference image. Operator Canopus must be able to AutoMatch the images. 204 Action Description Uses Image Stack (Average, Multi) Stacks multiple images using average value as one group or in groups of a certain number, e.g., you can stack 100 images in sets of three. None Canopus must be able to AutoMatch the images. Stack (Sum) The same as Add except that all images are registered. Greatly increases SNR. Noise reduction is not as great and may actually increase. The Operator image is the reference image. Operator Canopus must be able to AutoMatch the images. Result images are converted to 32-bit integer to avoid reaching saturation. Stack (Sum, Multi) Stacks multiple images using summed value as one group or in groups of a certain number, e.g., you can stack 100 images in sets of three. None Canopus must be able to AutoMatch the images. Result images are converted to 32-bit integer to avoid reaching saturation. Noise Reduction Reduces noise in the image by performing a median comparison of pixels in a 3x3 region around each pixel. If the pixel value varies from the median by more than a user-set amount, the median value of the 9 pixels is assigned to the pixel being examined. None Fix Column Same as Noise Reduction except that the operation is limited to a single column. None Resample Resamples one or more selected images to 8x, 4x, 2x, 1/2x, 1/4x, or 1/8x original size (uses “Factor” setting). None Pixel Math (Add) Adds a fixed value to each pixel in one or more selected images. Over and underflow checking is performed. None Pixel Math (Subtract) Subtracts a fixed value from each pixel in one or more selected images. Over and underflow checking is performed. None Pixel Math (Multiply) Multiplies each pixel value in one or more selected images by a fixed amount. Over and underflow checking is performed. None Pixel Math (Divide) Divides each pixel value in one or more selected images by a fixed amount. Over and underflow checking is performed as well as divide by zero. None Convert to 16-bit Converts one or more 8/32-bit integer or 32/64-bit floating point images to 16-bit integer. This is useful when working with other programs that cannot handle all of the FITS image formats. None Convert to 32-bit integer Converts one or more images to 32-bit integer format. None Convert to 32-bit float Converts one or more images to 32-bit floating point format. None 205 Action Description Uses Image Pad FITS to 2880 Pads the FITS header to a multiple of 2880 bytes filling with spaces (ASCI 32) and pads file to multiple of 2880 bytes, filling data beyond the image with ASCII 0. None Flop (left-right) Reverses pixel positions left-right (rotate 180° about Y-axis). None Flip (top-bottom) Reversed pixel positions top-bottom (rotate 180° about Xaxis). None Automatch (WCS) Automatches one or more images and inserts WCS information into FITS header. None Crop Crops images to reduce the number of rows and/or columns. None Select Files Click this button to display a Windows file selection form. Select one or more files and then click the Open button. The “Files selected” label changes to reflect how many files were selected for processing. If you click the Open button, any previous list of files is replaced to the new list. It is not possible to append to the file list. Clear Files Click this button to clear the internal list of images that have been selected for processing. The “Files selected” label will show zero files selected. Review Files The speed button immediately to the left of the Process button allows you to review/edit the list of selected files. Check the box next to the files you want to remove from the list, then click OK. Basic Steps for Image Processing Select a Dark, Flat, and/or Operator image as required by the processing method to be used. Using the file controls at the left side of the form, locate and select one or more files to be processed. The processed files are given the same name with '_P" added to the end and saved in the same directory. The original file extension is also maintained. If processing a previously processed image and the name ends in ‘_P’, e.g., M51_001_P.FIT, the file name is retained “as-is.” Click the Process button. Messages appear in the memo control to the right informing you of the progress for each image. A message box appears when the last image has been processed. 206 The details of how and why each type of operation is used extended beyond the scope of this manual. The reader is referred to any number of excellent books on the subject. Viewing Processed Images After most operations, the memo field on the right of the Files page contains a list of files that were processed. Double-click on a line in the memo to display the corresponding image on the Images page. Image Processing - Stacking Images Stacking images can result in significantly increased signal to noise ratio (SNR) and allow you to image up to a magnitude fainter (if you use 16 raw images). Those who cannot guide for long periods of times can use the stack feature to simulate exposures many times longer than the single image, usually with a better SNR. This is particularly true if using the Stack (Average) method since the noise tends to cancel out across many images. The increase in signal from each star does not grow as rapidly but neither does the noise. The important difference when using the Stack methods is that the images are registered. This means using the first image as the reference and then translating, rotating, and scaling each additional image so that it matches the first. With care, pixel positions are accurate to 1/20 (0.05) pixels and rotation angles are 0.01°. AutoMatch Required To avoid having to mark two reference stars on every image that you want to stack, Canopus AutoMatches the images after you specify two stars on a reference image. The RA and Declination of the pair are computed. As each image n the stack is read and AutoMatched, Canopus locates the pair via their RA/Dec in order to compute the necessary scaling, rotation, and translation to stack the image to the reference image. After the images are registered, they are added or averaged, depending on which method you selected. 1. For best results, process the images to be stacked with darks and flats. This creates a set of submaster images. 2. Select the desired Stack method. 3. Set the Operator field to the reference (first) image. 4. Select the images to be registered against the operator image. 5. Click the process button to start processing. A series of messages appears in the memo field. 6. The Operator image is displayed in a separate form. 7. To get the best possible registration, you must select two stars as far apart as possible, e.g., opposite corners. The same two stars must be present in all images to be stacked. 8. Move the mouse cursor over the first star and left click the mouse. The measuring apertures appear centered on the star. 207 9. Click the Set Star 1 button. The X/Y position of the star appears in the two controls to the left of the button. These controls are read-only, meaning you cannot manually enter the X/Y position. 10. Repeat step 8, selecting the second star instead. 11. Click the Set Star 2 button. The X/Y position of the star appears in the two controls to the left of the button. These controls are read-only, meaning you cannot manually enter the X/Y position. 12. Click the OK button to accept and register the positions with the program. If you click the Cancel button, the image is not used. You cannot go back and reset or select a rejected image. 13. Once you have registered the two stars on the reference image, Canopus goes through the process of registering each image against the first by locating the two reference stars on the image. This creates a temporary image on the hard drive. STACK0.FIT is the operator image, STACK1.FIT is the first image, etc. 14. After all the submasters have been created, Canopus then calls the Average or Sum method to perform to combine the submasters into a single master image. When the file save dialog appears, save the final image to the hard drive. Once the image is saved, it is loaded into the Images page and the form switches to that page so you can review the final image. If summing stacked images, the files are converted to 32-bit (if not already 32- or 64-bit). This avoids having pixels reach the 16-bit saturation level of 65535. It would take more than 32,000 images for a pixel at an ADU value of 65535 at the same spot on each image to reach saturation in a 32-bit image. Image Processing - Stacking (Multi) The Stack (Multi) feature is designed specifically for those doing time series work who take dozens or even hundreds of images on a given night and want to stack them in groups in order to get improve signal-to-noise. For example, could take the 100 images from a night’s run and stack them in groups of 3 images each. You can even specify if images are unique to a give group or can be used more than once. You can also determine the maximum separation in time between images in a group so that you don’t stack an image taken an hour after the other images in the stack. 208 Canopus must be able to AutoMatch the images that are being stacked. The Select Stack Sets Form This form defines the images involved in the stacking and how they will be grouped. You do not have to define the groups individually. Canopus does that automatically based on the setting and files that you select. X/Y Pairs Reference Image This is the image where you specify two stars that allow Canopus to match all the images. The pair of reference stars must be on all images, so if you’re working a moving target, chose the stars carefully. If necessary, you may have to run the stacking routine more than once in order to pick a different reference star pair for groups of images. Just as with regular stacking, this image will be displayed before the processing begins so that you can specify the reference pair. Output Directory Enter a valid director where the output files are to be saved. Use the speed button next to the field to locate or create a valid directory. Base Name Enter a base name for all output files. Canopus appends an auto-increment number to the name before saving. Auto Count Enter the number of images to be in each group. Max Sep. Enter the maximum time, in minutes, separating any two images in a group. This avoids merging images taken hours apart. Group Mode These radio buttons determine how the groups are formed from the set of images. Incremental Images are grouped 123, 234, 345, 456, … Bin Images are grouped 123, 456, 789, … The screen shot above shows images group with the Incremental option. IM Floor This is the lower limit of the instrumental magnitude for extracted stars. Any stars fainter than this limit will not be extracted from the image. Tolerance Enter the tolerance for matching, in pixels. This is how close each of the two reference stars must be to what Canopus thinks are the stars on an image being stacked. Too small a number could prevent images from being matched. Too large a number could allow matching to the wrong stars. For these reasons, the X/Y reference stars should be isolated, i.e., have no close companions. Overwrite files Check this box to have Canopus overwrite existing files. If sending the output files to a directory other than the source directory, this a good idea since you may want to change how images are grouped or the IM Floor. If this box is checked, the original output files are overwritten. If this is not checked, the auto-increment numbering will take over and you will have two sets of images, each with its own set of stacking rules. This may be what you want but it can also mean a large number of files on your hard drive that you may not want but can’t tell without opening them. Group Tree View This control displays the groups and the files within each group after you select a list of files. Click the “Add” button to add files to the list after first setting the grouping options. Click the “Delete” button to delete the highlighted group in the list. You cannot delete individual files. 209 Click the “Clear” button to remove all groups from the list. OK Click this button to start processing. Cancel Click this button to close the form without processing the groups. If you chose to overwrite files, a warning message appears. Click “Yes” to delete the files and continue processing. Click “No” to keep the existing files and abort processing. Setting the Reference Stars This works just as with regular stacking. Once you have set the two stars, click “OK” to continue. You can click the “Abort” button the Batch form to stop processing. Otherwise, the memo on the Files page keeps you informed on the progress of the stacking process. If you have lots of images, this can take some time since Canopus must extract the star data from each image. 210 The FITS Header is updated to use a start time (DATE-OBS keyword) that corresponds to the arithmetic mean of the mid-exposures less one-half the total exposure. This means that you can stack images of different exposures and still get a correct and that Canopus, when it reads the DATE-OBS keyword and exposure can compute the correct effective mid-exposure time. Image Processing - Editing FITS/SBIG Headers The main purpose behind the header editor is to allow correcting the date and/or time of an image due to computer problems or to modify some of the “comment” fields, such as instrumentation, the position of image center, and so on. Some fields cannot be edited, even though they are displayed. Mostly these are values that, if modified, would render the image unreadable, e.g. the number of pixels per row or column. These are shown as dark gray fields. The editor also allows adding additional standard keywords and associated values. It cannot be emphasized enough that using the header editor requires great care. If used incorrectly, an image can be rendered unreadable. It is a very good idea to backup any images that you intend to edit, just in case something does not go as planned. Forced Formatting vs. Free Form Data Entry Some header editors allow you to enter data with little or no validation. This can cause a number of problems when trying to read the image header after it is modified. On the other hand, forcing the format of many of the data fields can lead to problems when the original data was not stored in that format. For example, the MPO editor assumes the OBJCTRA field has a format of HH:MM:SS.sss. If another program stored the data with fewer characters than in that “picture mask”, then the data doesn’t look quite right when displayed in the editing field. In such a case and you do not need to modify the OBJCTRA field, then do not edit the original data. It will be saved “as-is”. However, if you do need to modify the data, you must enter a value that exactly fills the expected data mask. In addition to forcing the format of data entry, the editor also forces the data type for a given keyword. To help avoid the proliferation of non-standard keywords, only a limited number of keywords are allowed and no userdefined keywords can be added to a header. These restrictions are in place to help avoid making your images unreadable. See “FITS Keywords” at the end of this Guide for a complete list of the allowed keywords, the forced data type, and forced data (entry) mask. Some of the keywords listed are for SBIG format only. You should be careful not to add an SBIG keyword to a FITS header and vice versa. To help assure compatibility, at least in basic structure, all keywords for a FITS image are truncated to the first 8 characters. 211 Editing a FITS/SBIG Header - Single File Tab This tab is used to edit the values in a single image. Table The grid displays the keywords, data, and comment for each item in the header. The grid is read-only, meaning you cannot edit the data from it. Value (Current) This entry field displays the value for the selected keyword in the table. If the table entry is dark gray, the entry field is disabled. The entry field’s “picture mask”, used to assure proper data entry changes to match the associated keyword. If the keyword is not among those listed in FITS Keywords, the entry field defaults to a data type of “string”, allows any character, and has a maximum length of 70 characters. Save (Value) Click this button to save the value in the Value entry field. The table is updated to reflect the new value. Keyword This drop down list is used to add a new keyword to the header and displays the standard keywords that are not already in the header. The exceptions are COMMENT and HISTORY since multiple occurrences of these keywords are allowed. To add a keyword not in the header, select the keyword from the list. This automatically sets the data type and picture mask for the Value entry field under the drop down list. Value (New Keyword) This entry field is used to enter the value for the keyword being added to the header. See FITS Keywords for the data type and picture mask associated with a given keyword. Add Click this button to add the selected keyword and value to the header. The table is updated to include the new information. 212 Open Click this button to display a file open dialog and then select the image to be modified. The button is disabled while you are editing the header. Save (Header) Click this button to save the contents of the table to the image header. The changes you’ve made are not saved until you use this button. Cancel Click this button to cancel all changes you’ve made to the header and close the image with its original header information. Editing the Header for a Single Image Select Utilities | Image Processing | Edit header from the main menu. This displays an empty version of the header editor. Select the “Single File” tab. Click the Open button. This displays a file open dialog. Select an image. Changing a Value Move the highlighted cell in the table using the mouse or cursor keys to the row containing the keyword/value that you want to change. Set the new value in the Value entry field immediately below the table. Click the Save button next to the Value entry field. This updates the table with the new information. It is critical that you use the correct format for some entries. A good example is the DATE-OBS field. This entry must be in the form YYYY-MM-DDTHH:MM:SS where T is the literal character ‘T’. When using this format, the date and time must be Universal Date and Time. Deleting a Keyword Be careful when deleting a keyword. While the editor prevents you from deleting some keywords, it’s still possible to delete a keyword/value that is critical to a program trying to read or manipulate the image. To delete a field from the header, highlight the appropriate row press the Ctrl+Delete key on your keyboard. This displays a confirmation message. If you answer “Yes” the field is deleted. The table is updated to show the keyword/value was deleted. Some fields besides those darkened fields at the beginning of the table cannot be deleted, specifically the Date and Time fields. If you attempt to delete one of these fields, an error message is displayed and the field is not deleted. Adding a Keyword Select the keyword to be added from the “Keyword” drop down list. Enter the value for the keyword. See FITS Keywords for the data type and formatting for the available keywords. Click the Add button. The table is updated to show the new keyword and value. Remember that not all the keywords in the list are appropriate for both FITS and SBIG images. If you’re not sure which keywords are allowed, check the FITS and SBIG standards. 213 Saving Changes Click the “Save” button immediately under the “Open” button. A confirmation is displayed. Answer “Yes”. The data is written to the header of the image and the table is cleared. If editing a FITS image and the changes would cause the header size to go beyond an integral multiple of 2880 (the default FITS header block size), the header is automatically expanded to the next integral multiple, thus keeping it within the FITS standard. The SBIG header cannot be expanded beyond its maximum of 2048 bytes. Therefore, be careful when adding additional keywords. The editor truncates all keyword/value pairs that would try to go beyond the SBIG header limit. When writing the header, regardless of the image format, all entries other than COMMENT and HISTORY are written in the order they were in the table. The COMMENT and then HISTORY lines are grouped together at the end of the header, with the COMMENT lines coming first. Editing a FITS/SBIG Header - Batch Process Tab The Batch Process tab allows you to change the header for one or more images with a single pass. You do this by defining which keyword values are to be added or modified and then select one or more images against which to apply the changes. Table The table displays the keywords and values you have selected to be included in the batch process. The table does not display the contents of any given image header. In short, it’s a list of changes. If a keyword in the table is found in the header, the value for that keyword is replaced by the value in the table. If the keyword in the table is not found in the header, it and its associated value in the table are added to the image header. The exceptions are for the COMMENT and HISTORY keywords. Existing values for these two keywords are not changed. Instead, if a COMMENT or HISTORY keyword is included in the table, it is added to the image header. These are the only two keywords for which more than one entry in the table is allowed. Not all keywords are available for editing. Specifically, TIME, TIME-OBS, and UT are not allowed. Instead, the keyword TIMEOFFSET is included. It would seem very unlikely that you’d want to set the time in an image header to be the same for several images. Instead, you might want to correct a problem caused by the computer clock being off real time by a fixed amount. The TIMEOFFSET keyword is used to adjust the existing time in headers by a fixed amount and so correct the problem. 214 Value (Current) It is not possible to edit a value in the table directly. Instead, as you select a keyword in the table, its value is displayed in this edit field. As on the Single File page, the data entry (picture) mask is changed to agree with the keyword. See FITS Keywords for a listing of keywords, data types, and entry masks. Comment stars after first ‘/’ Check this box to have Canopus interpret anything after the first ‘/’ character in a FITS header line as a comment. The forward slash character ( / ) delimits the start of a comment after a value on a FITS header line. Sometimes the character is used within the value itself, and so Canopus incorrectly reads the line. For example, for the TELESCOPE keyword an entry might be TELESCOPE=0.35m f/8.1 Ritchey-Cretien / Building #1 If this box is checked, Canopus will interpret “8.1 Ritchey-Cretien / Building #1” as the comment instead of “Building #1”. Generally, comments are supposed to start in column 32 (FITS/NOFS standard) but this rule is rarely observed and so Canopus needs help in determining how to read lines that include more than one ‘/’ character or that character is intended to be part of the data. Save (Value) Click this button to change the value for the selected keyword to the value in the Value entry field. The table is updated to reflect the change. Keyword Use the drop down list to select the keyword that is to be changed or added. As you select a keyword, the Value entry field under this list is adjusted so that the data type and entry mask are changed to agree with the selected keyword. See FITS Keywords for a list of keywords, data types, and entry masks. Value (Keyword) Use this entry field to enter the value for the selected keyword that will be added to the table. Add Click this button to add the keyword displayed in the drop down list and the value the entry field below the drop down list to the table. Clear Click this button to clear the table of all entries. Process Click this button to display a file selection form where you select one or more images to process. Once you select the images, the entries in the table are applied to each image. Building the Batch Process Table Before you can process images, you must first have one or more entries in the batch process table. Adding a Keyword and Value 1. Select a keyword from the drop down list. 2. Enter the value for the keyword. 3. Click the Add button. The table is updated to show the additional keyword/value pair. Deleting a Keyword 1. Select the row with the keyword to be deleted. 2. Press Ctrl+Delete on your keyboard. This displays a confirmation message. Answer “Yes” to delete the keyword and its value from the table. If you do answer “Yes”, the table is updated to reflect the change. 215 Editing a Value in the Table 1. Select the row with the value you want to change. 2. Enter the new value in the Value entry field immediately below the table. 3. Click the Save button. The table is updated to display the new value. Processing Multiple Images Once you have built the Batch Process Table entries, you can process one or more images. 1. Click the Process button. This displays a file selection form where you can select one or more images. 2. Select the images to be edited and click the “Open” button on the file selection form. The status bar at the bottom of the image indicates which file is being processed and when the process is done. Date Rollover If you use the TIMEOFFSET keyword to change the time of the image, the editor also checks if the adjustment would alter the date. For example, if you apply a correction of -1 hour to all images, the time of an image with 00:23:00 would go to 23:23:00 on the previous date. In such a case, the editor alerts you by displaying a message as to which image was affected and automatically adjusting the date. You should note the name of each image and confirm that the date was properly set. 216 The User Star Form See the discussion of this form starting on page 132. 217 LONEOS Catalog Viewer The LONEOS catalog viewer allows you to review the stars in the LONEOS catalog. The data cannot be edited with this form. To manage the LONEOS catalog, you need to import the latest copy of the LONEOS data from the Lowell Observatory. Sort by Choose the sort order from the drop down list. Your options are by Name and Right Ascension Search for Enter the complete or a partial entry of a star based on the sort order. For example, if the sort order is RA, you would enter a Right Ascension value, e.g., 01. If you pause for a moment, the catalog repositions itself to the nearest match to the entry field contents. Stds. Only Check this box to display only Landolt standard field stars. 218 The MPC Report Editor While not a full-fledged word processor, the editor does have the common features of Copy (Ctrl+C), Cut (Ctrl+X), Paste (Ctrl+V), and Undo (Ctrl+Z). Save This saves the file under the current file name. You can also use Ctrl+S. To save under a different name, select File | Save as or press Ctrl+A. The caption at the top of the form shows the current file’s full path name. EMail When you have reviewed the report and it is satisfactory, save the file, and then click the E-mail button to invoke your default mail program. If the “To” field is set on the Configuration | EMail page, that address is automatically inserted into the “To” field of your mail editor. The EMF editor stays open so you can copy its contents to the clipboard and then paste to the EMail editor. If sending to the Minor Planet Center, make sure your EMail system does not word wrap before column 80. If it does, then save the file and send the EMF file as an attachment and do not paste it into your message. Close Closes the EMF editor. If you have modified the file since it was first displayed, you are prompted whether you want to save before closing, to close without saving, or to cancel the close request. 219 220 MPO PhotoRed Reference Manual 221 222 PhotoRed Overview PhotoRed stands for Photometric Reductions. This program is designed specifically to work in concert with Canopus to generate standard magnitudes, i.e., magnitudes based on the Johnson-Cousins BVRI and/or Sloan (SDSS) g’r’i’ systems. The purpose of PhotoRed is narrow in scope yet it has many of the basic features of Canopus so that you can keep switching between programs to a minimum. The primary functions of PhotoRed are 1. To measure images of standard fields. 2. To determine the nightly extinction and transform zero points. Extinction can be determined using a modified Hardie method on standard fields or the traditional instrumental magnitude vs. air mass method using data imported from Canopus or measured in PhotoRed. 3. To determine the transforms required to convert raw instrumental magnitudes into standard magnitudes. 4. To determine the color index for a target object and comparisons stars when the values are not previously known so that standard magnitudes can be computed. 5. To import Canopus data so that instrumental magnitudes in one or more observing sessions can be converted to standard magnitudes. 6. To export the converted Canopus data to files that can be imported into Canopus for lightcurve analysis based on standard magnitudes. PhotoRed is not a separate program but utility of Canopus. Because of this, tracking the two program windows does require a bit of understanding how child windows of a Windows program work. The details are explained under the section on the Main Menu. Also, the configuration for PhotoRed has been simplified to include only those settings specific to it. The general profile under which the settings are stored are the same as the current ones for Canopus. The Users Guide The Users Guide (found in \MPO\DOCS) contains a number of lessons on using PhotoRed. Do not overlook this resource! You will probably find it much easier to understand the program by stepping through those lessons first, even if you don’t understand all the details. Once you have a grasp of the mechanics and general concepts, then reading the Reference Guide will fill in the details without losing sight of the “big picture.” 223 About Clear to Other Band Conversions In addition to the traditional photometric reductions, PhotoRed has been designed to convert observations made with a Clear (or no) filter to any of the standard Johnson-Cousins or SDSS bands. For any one hoping to work fainter targets, the loss of 0.5 to 1.0m when using filters is of considerable concern. First, and most important, it must be made clear that it is very unlikely one can get a perfect match of an unfiltered system to the standard. Don’t expect 0.01m or better – at least consistently. Therefore, the unfiltered system will have color dependencies that cannot be easily factored. Yet, the situation is not hopeless. PhotoRed treats the clear filter as if it were the standard filters. When catalog values are needed, magnitudes of the selected band from the catalog are used. Furthermore, since almost all the reduction methods use color index values in the standard bands, i.e., B-V, V-R, V-I, g’-r’, or r’-i’, the first- and second-order color dependency of the transform is part of the Clear transforms. The assumption is that the color dependency is linear, as it generally is for the standard filters. This assumption is good for most cases, though its effects should never be entirely discounted. Using V, R, and C images of M67 at the Palmer Divide Observatory, PhotoRed was able to reduce C observations such that the mean error from the actual V magnitude was generally < 0.02 mag and the standard deviation was on the order of 0.01m. Throughout the rest of this manual, reference to the C filter will mean a Clear filter (used to maintain optical depth) or “No” filter (unfiltered). The Main Form Pages The PhotoRed main form contains three main pages where the primary functions of the program are carried out. You can switch among the pages using the Pages item on the main menu, or via the keyboard by pressing the Ctrl key along with a number from 1 to 3 (using the keys on the top row of the keyboard, not the number pad keys). Measurement Page (Ctrl+1) This page is where you load images of standard fields, generate the matching chart, and measure the images before performing the reductions. Reductions Page (Ctrl+2) This page is where you can sort and modify the data used to perform the reductions and then run a specific reduction routine. Charts Page (Ctrl+3) This page allows you to view plots of the data used to determine various reduction values. It’s important that you review the plots after running each routine so that you can verify the validity of the solution. Sometimes including or excluding a single data point can dramatically alter a solution. To-do List Help PhotoRed is probably not the most intuitive program you’ll use. Then again, photometric reductions are not the most intuitive work you’ll do. However, every effort has been made to make getting standard magnitudes as easy and efficient as possible. Still, there’s lot to remember and so PhotoRed now has a “To-Do List” help feature to remind you of the basic steps required for each reductions method. Using the To-Do List Select Help | Show Reductions Help from the main menu to display the To-Do List help. This places a checkmark next to the menu and displays the To-Do List on the right side of the main form. 224 To-Do List Selector Use the drop down box to select which to-do list you want displayed. By default, the list that appears when you first display the help matches the reduction method you have selected. There is a help list for each of the reduction methods. List Checkboxes The checkboxes within the list are enabled so that you can check each one as you complete the step. However, the state of the boxes is not saved from one session to the next and checking or unchecking has no other effect. Think of them as part of an erasable to-do list. Page Turner Note the gray “page-turner” at the bottom right of the to-do list. If you see this on one or both bottom corners of the to-do list, it means the list is continued or has previous items. Click on the page-turner to see either the previous or next page of the to-do list. Since the to-do list changes size in step with the main form, the turners may become visible or hide themselves as needed. Auto-hide when Printing or Saving a Plot When you print or save a plot, its final size is dictated by its size on the screen. The To-Do list compresses the horizontal dimension of the plot area, which affects the printed or saved plot. Therefore, whenever you print or save a plot and the To-Do List is visible, PhotoRed temporarily hides the To-Do List – expanding the plot – and then re-displays the ToDo List. Image Processing Image processing is the same as provided in Canopus, which offers image manipulation essential to basic astrometry and photometry. This includes scaling by several methods, creating a master dark, creating a master flat, and adding a master dark and /or flat to a raw image as the image is loaded. Other options include stack and average, add/subtract/multiply/divide, and resampling. For a detailed discussion about the image processing features in Canopus and PhotoRed, see the relevant sections starting on page 197. Main Menu Most of the features in PhotoRed are accessed via the main menu and its submenus. In some cases, you access the menu item using the keyboard by pressing a specific key combination. For example, to display the Configuration form, press Ctrl+C, meaning you should depress and hold the Ctrl key while you press the ‘C’ key and then release both. Main Menu - File Menu Configuration This displays the Configuration form where default settings for PhotoRed are made and saved. See “PhotoRed Configuration” on page 229 for details about configuring PhotoRed. Exit This closes PhotoRed and all open forms. All data is not saved automatically so be sure to save any work before you close the program. Use Alt+X to invoke this menu item via the keyboard. 225 Main Menu - Image Menu Most of the items on this menu are identical to those in Canopus. The chart matching behavior is slightly different, as will be explained later. See the discussion of this menu under Canopus starting on page 15. Main Menu - Photometry Menu The Photometry menu is used to load, save, and output observation data. It’s also used to review the current transformation values. Photometry Wizard This menu item invokes the one of two Photometry Wizard forms. These allow you to measure a series of images of the same standard field quickly. Open Image List This menu item opens the Image List form, which displays and measures the images based on the setup from the Photometry Wizards. Load Observations This menu item allows you to load previously saved observations. See “Working with the Observations Data” (pg 238). Save Observations This menu item allows you to save the current observation data under the same or different name. See “Working with the Observations Data” (pg 238). Clear Observations This menu items clears the internal lists. See “Working with the Observations Data” (pg 238). Print Observations This menu item prints the data currently displayed on the reductions page. Full Details to Text This menu item sends all observation data to a text file that can be reviewed at a later time or imported into a different program. Transforms values This menu item displays the transforms form where you can review and edit the values used for photometric reductions. Backup saved transforms Click this menu item to display a file save form. Enter a file name and save the currently saved transforms. This may not be the same as those stored in memory and displayed in the transforms form. When you run a reduction mention, the derived values displayed in the transforms form are not recorded automatically to the hard drive. You must use the Save button on the transforms form to save the settings. Load saved transforms Click this menu item to read the settings in a file created with the Backup saved transforms menu option. Those settings from that file are then transferred to the “in-memory” transforms values and are saved to the hard disk to replace the previously saved transforms. If the transforms form is open, the values in its entry fields are updated to reflect the values that were just restored. Main Menu - Plots Menu The Plots menu allows you to save plots after running most reduction methods. There is a menu item for every filter and the comparisons tabs on the Plots pages. 226 Save Displays a file save dialog. You can save the plot as a Windows bitmap (BMP) or compressed, nearly lossless PNG file. Main Menu - Utilities Menu The Utilities menu runs the routines that import and export Canopus data and that allow you to manage the several user-defined data tables. Import Canopus Session The data imported from Canopus is used to determine the extinction coefficients using the instrumental magnitude vs. air mass method and/or converted to standard magnitudes before being exported back to Canopus. See “Working with Data from Canopus” (pg 236). There are three choices under this item From PHSESS This allows importing one or more sessions from the main sessions and observations files (PHSESS/PHOBS). From Exported Sessions | Multiple files w/one session This is for importing data from one or more export set files where each SESS/OBS pair has data for only one session. If you select a file that has more than one session, data from only the first session is imported and a warning message is displayed. If you want data from the other sessions, use the option below. From Exported Sessions | One file w/multiple sessions This is a combination of the two options above. You select a SESS file with multiple sessions and a form appears that allows you to select one or more sessions. Data from the selected sessions is then imported. Export to Canopus This menu items exports data that was imported from Canopus to two files that can be imported into Canopus for analysis. The exported files contain the same data and are in the same format as if you saved specific sessions in Canopus. See “Working with Data from Canopus” (pg 236). Clear Lists This menu item clears the two lists involved when importing data from Canopus (the “normal” observations data involves only one list). Image processing This displays the image processing submenu. The submenus allow you to convert FITS to SBIG, SBIG to FITS, edit the headers for FITS and SBIG files, and do batch image processing. User Star Management This menu item displays the User Star management form, which allows you to enter data for photometric references manually or to import the sequences produced by Arne Henden at USNO. See The User Star Form. The form in Canopus and PhotoRed are the same. The only difference is from where in the program you access the form. View LONEOS This menu item displays a read-only version of the LONEOS catalog to help you look up information about stars in that catalog. AAVSO Data Management This displays the AAVSO data management form. Variable star observers will find this feature particularly handy as it does differential transforms and target measurement in a single step. Generate Batch Reference File This displays the Batch Reference File Generator form. This form provides the necessary information to locate the comps, check, and targets on images as well as their magnitudes and color indices for transforms reduction during AAVSO batch processing. 227 Main Menu - Pages Menu The Pages Menu allows you to switch among the three main pages of the program and so access the features for a given page. You can use the keyboard to accomplish the same effect. Press Ctrl+Number, where Number is the 1, 2 or 3 key on the top row of the keyboard. Pressing the number keys on the number pad does not work. Main Menu - Help Menu The Help Menu accesses the on-line help system and displays information about PhotoRed. Contents Use this item to display the Context and Index pages of the Help system. Show Reductions Help Check this menu item to display the “To-do List” help. This help system displays the essential steps in a window to the right side of the main form. Uncheck the menu item to hide the display. About This item displays PhotoRed version information. Main Menu - Canopus Menu This menu allows you to hide Canopus or force it to be the topmost window. Hide Canopus This menu item does not minimize the Canopus form – that would also minimize the PhotoRed form. Instead, it actually hides the Canopus main form. Bring Canopus to front This menu item forces the Canopus main form to be visible to make it the uppermost window on the desktop. 228 Configuration The configuration form is access by selecting File | Configuration from the main menu, clicking the configuration speed button on the main tool bar, or entering Ctrl+C from the keyboard. The PhotoRed configuration displays a subset of the settings of the current profile in Canopus. When you edit one, you are editing the other. You cannot create, edit, or delete profiles in PhotoRed. Instead, the profile being used by Canopus is the used by PhotoRed. This avoids considerable confusion when invoking more than one instance of Canopus, which is now possible. Since the details of the configuration form are identical to those in Canopus, please refer to the Canopus section for additional information. Configuration – General Page See page 27. Configuration – Catalogs Page See page 34. Configuration – Charting Page See page 36. 229 230 Using PhotoRed While doing research for PhotoRed, it seemed that there are about as many ways to go about deriving photometric transforms as there are people trying to do them. What PhotoRed attempts to do is take the most common aspects of those many approaches and put them into a single, simple to use process. Even so, getting good photometric transforms requires skill, patience, and practice. Like any other software, PhotoRed is a tool but even the best tools require someone to wield them properly to get the job done right. Before getting down to measuring images and determining transforms, you should understand how and why PhotoRed implements its routines so that you can properly judge the results. From here on, the C filter should be taken to mean the Clear (or no) filter. Not Just for Asteroids Canopus and PhotoRed were originally written with asteroids in mind but they are by no means limited to that type of target. In fact, PhotoRed now has several features specifically designed for the variable star observer. Canopus includes a Time of Minimum (Maximum) calculator and can use Heliocentric JD for analysis. Canopus also has a variable star search program that automatically measures images – often for time-series work on an asteroid or variable star. There’s no reason to think that Canopus and PhotoRed are just for those with rocks in their heads. Using PhotoRed - The PhotoRed Philosophy As noted above, there are many ways to go about photometric reductions. Any program aimed at photometric reductions, including a spread sheet, must adopt one of those methods and ask that the user follow procedures that allow those methods to work. As long as there is solid foundation in the approach and its results are valid by design and not by chance, then there is no harm in adopting that approach. Derived Mags in Canopus Canopus can find DerivedMags directly (see starting pg. 25). Depending on the quality of the catalog magnitudes and providing that all the comparisons are similar in color to the target, the results should be very good to excellent. Canopus allows even more accuracy by applying terms for color index differences between target and comparisons and second order extinction terms, usually important when using B or Clear filter. By definition, V and R have zero second-order corrections, but that is something that you should confirm for your system. I have not found references that discuss second order terms for the Sloan filters. Again, when in doubt, measure and confirm. If working mostly in Canopus, you still need PhotoRed to find the transforms and second-order terms for your system. If the comparison stars you’re using are not part of a sequence, i.e., at least the level of secondary standards, you should also use PhotoRed to find accurate catalog magnitudes for the comparison stars used in Canopus. That is done in PhotoRed by first establishing the nightly zero point and then applying all the correction terms to a small subset of Canopus observations that are imported into PhotoRed. Working in One Filter PhotoRed departs from many reduction packages in that it does not find final magnitudes expressed as a color index but, instead, finds the reduced magnitude for the given filter. For example, it’s common to find B-V and V but not B directly. PhotoRed finds B directly. The standard approach is to find a set of transforms that equate an instrumental color index, say b-v, to a standard value, B-V. The conversion to standard V then requires having that instrumental color index, which is converted to the standard color index using the transforms. If the bulk of your observations are in one and only one color, then you would not have an instrumental color index for each observation and would have to use an assumed value. The differential formulae in PhotoRed require the standard color index to convert the target’s instrumental magnitudes to standard. If working in the standard approach, this means you’d need a B and V observation to find a single V value. With PhotoRed’s approach, you find the standard color index for the comps and target using a minimum number of images in two standard filters before you run the method to find the target’s standard magnitude. This means you get observations in only one color the bulk of the night to reduce the target to standard magnitudes. 231 Note that the air mass and extinction terms are not required. This is because under all but unusual circumstances, the values of the terms drop out because one is taking a difference instead of absolute values (this is not true for second order extinction, which is discussed later). Once standardized magnitudes are obtained for the comparisons, it’s a simple matter to find the target’s standard magnitude using the differential values in combination with those comparison standard magnitudes. Some would argue, rightly so, that you can do this anyway by simply using a single reference star’s data in the one filter to find the offset of the comparison star(s) and so find the standard magnitude of the target. This is true if one can safely assume the comparisons are close in color to the target and reference star. The PhotoRed approach, without adding too much additional work and complexity, allows a more flexible selection of comparison and reduces the color errors by not making those assumptions. Using PhotoRed - First Order Extinctions – Is This Trip Necessary Plain and simple: No, you do not need to find first order extinction terms, save maybe a few times a year to determine a good average value for each filter. This will shock many, but if you take a close look at the full formula to get a standard magnitude from an instrumental magnitude, you can see why. What follows is for the V band but applies to all others in the same way. V = v – k’vX – k”vCIX + TvCI + ZPv where V v k’ X k” CI Tv ZPv standard magnitude of the object instrumental magnitude of the object in the V filter first order extinction for the V filter air mass of the object second order extinction for the V filter color index of the object (e.g., B-V, V-R, etc.) transform for the V filter nightly zero point for the V filter By holding the second order, color index, and air mass terms constant for the moment, any change in k’ changes the value of V by the same amount as the change in k’. For example, let’s plug in numbers, using 0 for those values being held constant, except air mass, where we’ll use 1. First, well assume k’ = 0.2 and that V = 14.0 (the true magnitude of the object). 14.0 = = 14.0 – ZPv = ZPv = ZPv = 0 – 0.2(1) – k”v(0) + Tv(0) + ZPv –0.2 + ZPv –0.2 14.0 + 0.2 14.2 If k’ = 0.3 then this becomes 14.0 – ZPv = ZPv = ZPv = –0.3 14.0 + 0.3 14.3 From this, it is clear that a change in the first order term requires an equal change in the nightly zero point to find the same value for V. Put another way, you can use any positive, non-zero value for first order extinction to determine the nightly zero point and then apply those two values to the reduction formula and get the same result as if you had used the “true” values. 232 It should go without saying that the presumption is that conditions are the same for all times the reduction terms are determined and applied, i.e., for the reference field when finding the nightly zero point and for the target field when finding the comparison star magnitudes. Passing clouds, thickening haze, dew, frost, and all the other things that go bump in the night void the above discussion. Second Order Extinction – The Trip Is Necessary It is important to emphasize that the above applies only to first order extinction – not second order. The latter has dependencies on both color and air mass. Therefore, you must determine this term for each filter. The good news is that the term is based on your system and so you need to find it only occasionally, say 2-4 times a year, or if your system changes. Using PhotoRed - Getting and Measuring Images Either you’re going to reduce to standard magnitudes or you’re not. This means you have one of two paths to follow on any given night. If you’re selecting the first and are just doing time-series work on a pure instrumental system without trying to merge data from more than one night or use it in cooperation with other observers, you can stop now and work only with Canopus. The rest of you – read on. The second path using PhotoRed is relatively easily. The step of finding first order extinction (FOE) can probably be avoided in many cases. If you’re going to be working multiple fields over a range of air mass values, then you must find the nightly zero point using an actual or assumed first order term. This can be done easily by using the Modified Hardie method, which not only finds the FOE but can reset the nightly zero point when using a given set of transforms. If you don’t have the transforms, then one of the two fields used for the Hardie method can be used to get the transforms first. You should determine the second order extinction term for each filter before you do transforms. Otherwise, that term is not removed from the instrumental magnitudes and so, in reality, you’re finding a first order extinction that merges first and second order terms. What are Good Values for Extinction? If you decide to get first order extinction (FOE) values, the question becomes, “What are reasonable values?” Before that, some might ask wonder just what the value represents. In short, it is the magnitudes that a star dims per unit of air mass in a given filter. The air mass is 1.00 at the zenith and some large number at the horizon (it would be infinity except that the Earth’s atmosphere is not infinitely thick). The extinction value is used to convert instrumental magnitudes to a magnitude that would be obtained if the observations were carried out above the earth’s atmosphere (exoatmospheric). As noted in the section, “First Order Extinctions – Is this Trip Necessary?” it is not absolutely required to go through the process to get first order extinction values You can use some reasonable non-zero value based on experience or previous determinations. The “true” value for first order extinction depends on many factors but, in general, for V should be around 0.15 to 0.3 (the higher value for those near sea level). B will be larger because blue light is scattered more at low elevations and so less light reaches the observer. R should be close to V but just a little less since V is closer to B. As a check, the difference between V and R is usually on the order of 0.05. None of the values should ever be negative! Things do not get brighter as they move towards the horizon. When Conditions are Not the Best The sky being a bit hazy or having occasional cloudiness may not prevent you from getting data of your program field (if you’re working with differential photometry) but it should give you pause when determining extinction and, most especially, transform values. If conditions are dubious for transforms but still allow working the program field, then do so without worrying about getting the images for transforms. Go back some later evening when conditions are good and perform only those steps required to determine the transforms and the standard magnitudes for stars in the program field. You can then apply those to the differential magnitudes you obtained in the earlier session to standard magnitudes for the target. In fact professionals often use this general process, especially when working targets that move, i.e., asteroids. Data Acquisition and Reduction Outlines The outlines in following sections give you the basic steps for using the various reduction approaches provided by Canopus and PhotoRed. Use them as a guide to getting started and let experience and practice take you the rest of the way. 233 It’s always best to start slowly and progress as you learn more about the various processes. In that light, if you’re doing asteroid work and the target doesn’t have a long period or difficult solution so that you have to follow it for weeks, then try doing only C observations with no reductions. This allows you to concentrate on getting good data in a single color (Clear) and doing period analysis. Variable star observations are usually done in at least the V filter. However, in some cases it’s OK to do C only, e.g., timing of minimum for some eclipsing binaries or cataclysmic variables. I’ll again mention the Users Guide found in \MPO\DOCS. This contains lessons using sample images for all the main functions in PhotoRed, in particular a more detailed look at AAVSO batch processing. Please make use of this resource! Choosing the Second Filter For basic work, you can use only one filter. On the other hand, you may monitoring color changes of a variable through its cycle, and so – of course – will be using more than one filter. For those doing basic work, there might be times when you need to get multicolor observations. Mostly, these will be when you don’t know or want to refine the color index values for the comparison stars and target in you observations. If you have or want to use assumed values, then you can stick with one-filter observations. The advantage to doing at least some multi-filter observations of a reference filed is that you can establish what’s called hidden transforms for your system. For example, you can determine a transform that converts an instrumental v-r magnitude into a standard V-R. Then, when you do want do determine the standard color index of a star or other object, you simply get a few images of it in the two filters (V and R in this case), find the average instrumental color index and plug it into the hidden transform. You now have the standard color index of the object. If you do want to use a second filter for color index determinations and you’re working in V, then you would usually choose B, R, or I for your second filter. Which one should you use? It’s not necessarily an easy answer. In a time past, the second filter would have been B since B-V color indices are almost always determined for reference stars. This will be the case for the AAVSO APASS catalog. However, with CCD cameras – which are OK in B but much better in V, R, and I – the better choice is maybe R or I. V-I gives a larger color difference and so would seem a good choice except that I magnitudes are hard to find. V-R is more likely to have the necessary catalog values but there’s no certainty. V-R has also been shown to be the right choice for certain studies that try to find the distance to stars based on apparent magnitudes, color indices, and other factors. Try V-R at first and see how that works. You’ll avoid the relative low sensitivity issues in B and – for those with back-illuminated cameras – problems with “IR fringing”, which cannot be easily removed with flat fields. Remember that while you can find the transform for a given color based on any color index, e.g., R in terms of V-R or B-V, there must be catalog values for that color when finding the transforms. For example, you can’t find a transform for R without having R magnitudes available in the catalog. For Sloan filters, the common color indexes supported in PhotoRed are g-r and r-i. Choosing Reference Fields For highest accuracy, you should use Landolt fields for the reference images. If you use the LONEOS or Henden sequences, keep in mind that they are not true standard. Carefully selected Henden fields, using stars with at least three observations and a maximum Verror of 0.02m, can get you very close and will suffice for most work. These have been selected for having a good number of stars within a smaller region. 234 Landolt fields should be your first choice and only choice if doing all-sky photometry to generate photometric sequences for a new field or trying to do critical work. If the field is not near your target field, then you must use at least good estimates of first order extinctions, or actually find them, before you run the transforms, color index, and standard magnitudes routines. Using the Transformed Data in Canopus When you run the Standard Magnitudes – Target routine on data imported from Canopus, and you then export the data back to Canopus compatible files, the CompXMag fields in the observations data table are forced to 0.0. The ObjMag field is set to the derived standard magnitude of the target (see the Canopus manual discussion on the Sessions form for more information). In addition, the DeltaComp value on the Sessions form is set to 0.0. This makes the data akin to importing JD/magnitude pairs from a text file with the magnitudes being standard magnitudes. In theory, you should be able to match all sessions of the target in Canopus without having to change the DeltaComp value because Canopus includes corrections for distance and changing geometry. However, since the phase coefficient, G, is not always well known and there are bound to be both random and systematic errors. You do your best to reduce the latter and hope for the best on the former but – in the end – you may have to adjust the DeltaComp value slightly to get curves to match up perfectly. Of course, variable star observers don’t have to worry about the value of G, just the systematic and random errors. Using PhotoRed - The Measurements Page When displaying larger images, PhotoRed features a splitter bar that can be automatically switched to a full view of either the chart or image or back to an even split of both. The process of generating the chart for astrometry or photometry is discussed in “Generating a Chart for Astrometry” on page 115. This is required only if PhotoRed cannot determine the position of the object from the image header or you choose to use the manual chart matching method. Switching Views on the Measurement Page When you first load an image or generate a chart, the vertical splitter is set to the center, evenly displaying the area for the chart and image. To change between full views of the chart or the image or to center the splitter between the two, click on the appropriate button at the upper left of the page. 1. The Left arrow (or <Ctrl+Alt+I>) moves the splitter to the far left. This displays the image only. 2. The Up arrow (or <Ctrl+Alt+S>) centers the splitter, showing an even amount of the chart and image. 3. The right arrow (or <Ctrl+Alt+C>) moves the splitter to the far right. This displays the chart only. The Users Guide See the “Core Operations” chapter of the Users Guide for quick lessons on: 1. Loading images 235 2. Generating charts for AutoMatch and Manual Matching 3. Setting the measuring apertures Using PhotoRed – Working with Data from Canopus PhotoRed provides several routines that work directly and only on data imported from Canopus. These routines eventually provide standardized magnitudes in Canopus compatible files that can be used for lightcurve analysis in Canopus. Having standardized magnitudes makes matching data from various sessions easier and more reliable. See the “PhotoRed” for tutorials on importing data from and exporting data to Canopus. The following section provides some additional information about the forms and methods used in those tutorials. Importing Data from Canopus This is a multiple select list that displays the Session number, Object name, Start Date and Time for the session, and the Filter used for the session. Sort by Select the sort order from the drop down list. The options are Session, Name, Date Search Type in all or part of any entry that is appropriate for the selected sort order to find the closest match. To select a single session Click on it in the list. The symbol in the fixed column at far left changes to a dot within a “>”, as shown in the lefthand screen shot above. To select multiple sessions Click on any one of the sessions to be imported.. <Ctrl+Click> to select or unselect any other sessions in the list (as shown in right-hand screen shot above. You cannot use <Shift+Click> to select a range of contiguous sessions. You must select them individually. Click OK to import the selected session or sessions. 236 If the row indicator is a solid black arrow, that row is not selected even if it’s highlighted. The dots tell you the rows (sessions) have been selected. The arrow only tells you that the highlighted row is the current row but it is NOT selected. If the symbol includes the dot within the arrow, as seen in both screen shots above, then that row is not only the active row but has been selected to be imported. When importing multiple sessions, those sessions should be directly related, i.e., they are of the same general time but differ only in the filter used. For a “normal” target, one where you use the same comparisons for the entire night, this would mean importing the same number of sessions as filters through which you observed. If working a fast moving target such as an NEO, things are a bit different. Filter considerations aside, you would probably have several sessions, with each session having its own set of comparison stars. If you’re doing filtered observations as well, then you would have, for example, three sessions (for V, R, C) that used the same comparison stars. You would also have another three for when you had to move the scope to keep the target in the field and so used different comparisons. This would continue through the night. In this case, you should follow the rule of thumb that the imported sessions should be on the same night and use the same comparison stars. Automatic Grouping PhotoRed groups observations to simulate them being taken at essentially the same time, i.e., as if you had a multichannel system. When data is imported from Canopus, PhotoRed tries to automatically group observations by comparing the date/time of the observations along with the filter, name of the object, etc. Depending on how quickly you took images, PhotoRed may not be able to determine the groupings correctly. You should confirm that the data is properly grouped before starting analysis. See Working with the Observation Data for information on how to change the group number assignments in the observation data. Once you’ve imported data, you can treat it pretty much the same as if you had measured images in PhotoRed. Running some of the routines may not make sense, e.g., the Hardie first order extinction and transforms - though the latter might be possible if the field contains standard stars. See next section for more information about grouping and editing the data. One thing you cannot do with imported data is save it as you can “normal” observation data. This goes back to what was mentioned above about there being two lists and, in particular, the second list that links the observations in PhotoRed to the session data in Canopus. The transient nature of the Canopus sessions files precludes saving the data in PhotoRed for later use. Exporting Data to Canopus See the tutorial in the Users Guide for exporting data to export sets for use in Canopus. 237 Using PhotoRed – Working with Observation Data The observations data list, on the Reductions Page, displays all the data that can be used in the various reduction routines. You can group observations in several ways and sort the data within the groupings by the entries in several columns. You can also change the USE status flag for one or more observations at a time, as well as the group number and filter, and delete one or more observations from the list entirely. Grouping the Data To group the data, drop down the list at the upper left of the observations list area and select the desired grouping. Group by Filters Groups data by the filter used for the image Group by Name Groups the data by the name of the object All No grouping. All fields are shown. Group by Group Groups the data by group number. Sorting the Data You can sort the data even when it is grouped. For example, you may have the data grouped by name but you can then sort the data by date, group, air mass, SNR, or filter. If you click on a column header and an up or down arrow appears to the far right of the header, that column can be sorted. Sizing Columns You can adjust the size of the columns when viewing the data. Move the mouse cursor over the line between two columns, depress the left mouse button, and then drag the mouse to resize the column. Release the mouse button to 238 stop resizing. The sizes are remembered as you switch from one grouping view to another and are saved when you close the program. Editing the Data To display the editing menu, right click over the observations list. Expand all If the list is grouped, this expands the groups so that all observations are visible. Collapse all If the list is grouped, this collapses all groups so that only the group headers are seen, i.e., no data is displayed. Toggle Use Status This menu item reverses the USE flag for all selected items, i.e., True becomes False and vice versa. Set USE to True This menu item sets the USE flag for all selected items to True. Set USE to False This menu item sets the USE flag for all selected items to False. Set Group Number This menu item allows you to change the group number for selected items. When you select this menu option, an input form appears. Enter a number greater than 0 and then click OK to change the group number. If you click Cancel, the group number is not changed. Set Filter This menu items allows you to change the filter for the selected items. This might be necessary because you had the wrong filter set when making Canopus measurements or forgot to change the filter setting while using the Photometry Wizard. When you select this item, an input form appears. Click the appropriate radio button and then the OK button to change the filter. Click Cancel to quit the operation without changing the filter setting. Delete Observation This menu item allows you to delete one or more items from the observations list. 239 Loading and Saving Observations PhotoRed allows you to save a set of observation data and reload it for analysis at a later time. This applies to data measured in PhotoRed only. You cannot save or reload observation data that is the result of importing data from Canopus. This is because when the data is imported from Canopus, there is a second internal list involved that is derived from information available in the Canopus files and cannot be easily reconstructed by simply loading a standard observations list. To Save Observations Select Photometry | Save Observations from the main menu. This displays a file save form. Locate the directory and enter the file name and then click Save. A warning is displayed if the file already exists. To Load Observations Select Photometry | Load Observations from the main menu. This displays a file open form. Locate the file to be opened and click Open. To Clear the Observations List Select Photometry | Clear Observations. This displays a warning message. Answer “Yes” to clear the list. Using PhotoRed - Locating Data Points on the Plots For most plots, when you click on a data point, information about that point appears in the status bar in the lower right corner of the main form. The information includes the name of the object, the group number in parentheses, and the X/Y values of the data (not the X/Y screen pixel values). You can use this information to help exclude bad data points from the calculations by going to the observations data list on the Reductions Page and setting the USE flag to False for the given star. 240 The Photometry Wizards There are two photometry wizards in PhotoRed. Transforms Wizard This is used to measure reference fields for Transforms and the Quick Binzel routine. The Differential Photometry Wizard This is almost an exact duplicate of the Lightcurve Wizard in Canopus. This wizard allows you to measure a number of images taken for the specific purpose of finding the color index values of the comparisons and target or for quick measurements when you don't want to create a session in Canopus with a small number of observations. The process takes only a few minutes so that you can quickly move on to working with Canopus data. Users Guide The User’s Guide “PhotoRed” chapter includes several lessons on using the Wizards in PhotoRed. The following sections give additional information and details about entry fields on various forms. The PhotoRed Image List You'll use the PhotoRed Image List (the List) to measured images for almost every reduction method in PhotoRed. So, before you start using the wizards, you should be familiar with some of the features of the Image List form and which have a direct effect on the data to be reduced. The Image List appears after running a wizard and selecting a set of files to be measured. The list box at the top displays those files you selected. The List is similar to but not exactly the same as the one used in Canopus. For one, the Auto button is not available on the PhotoRed Image List form. Since you don’t normally measure more than a few images and you want to keep tight control on things when finding transforms, the slight inconvenience of having to click the Accept button (or pressing <ENTER>) is a fair trade-off. Group Depending on the reduction method to be used, the observation data need to be placed either into a single group or multiple groups. Placing all the observations into a single group allows them to be treated as if they were taken at essentially the same time. Breaking the data into two or more groups is usually done when wanting to get an average of several observations and a good measure of the error (standard deviation). Even when data are placed into a single group, an average and standard deviation are still determined and reported. See the discussions for each of the reduction routines for more information. The Group entry field allows you to set the group number manually before recording the data for the observation. When all observations are going into a single group, you would enter a non-zero number in this field, set the Increment radio group to “None”, and proceed with measuring the images, i.e., “set it and forget it.” If you're splitting the observations into two or more groups, this can be very tedious and subject to error. In this case, the “Mod” entry field and “Increment” radio button group are used to increment the group number automatically. 241 Even when using one of the auto-increment options, you can manually override the group number assigned to the observation by changing the value in the Group entry field. Increment Radio Group This control determines if the Group number entry field value is automatically incremented as you measure images. How the group number changes is based on the selection and, in one case, the setting of the "Mod" entry field. None Select this option to have the Image List keep the Group number value the same for all measurements, i.e., the value is not incremented but kept constant. You would use this option when wanting to put all observations into one group. List Index Select this option to force the Number to match the index of the image in the list plus one; the index is zerobased, i.e., the first image has and index 0, not 1. For example, for the first image, Group = 1; for the second image, Group = 2, and so on. Index mod X Select this option to have the group number equal the remainder of the index of the image in the list divided by the value in the Mod entry field. Remember that the first item has an index of 0 and not 1. For example, if the Mod entry field is set to 3, then the group number is the remainder of the index divided by 3, i.e., Index / Mod +1 1 2 3 4 5 6 Group 1 2 3 1 2 3 This option is often used when wanting to split observations involving multiple filters into different groups. For example, say you took a series of VRVRVR images and want to put them into three groups with a V and R image in each group. After selecting the images and just before the List appears, a message appears. If the images were taken in the order shown above, you would select "No", so that the images are sorted first by name and then by date. The result would be as shown in the screen shot of the Image List at the start of this section. You would set the Mod entry field to 3 and select the Index mod X option. The first R image would go into group 1, the second into 2, and the third into 3. When the first V image is loaded, the group value would be reset to 1, putting it in the same group with the first R image. The remaining two V images would be grouped with their R counterparts automatically. Index div X Select this option to have the group number equal the integer portion of the index of the image in the list divided by the value in the Mod entry field. Remember that the first item has an index of 0 and not 1. For example, if the Mod entry field is set to 3, then the list will “bin” the images as it goes through the list and so the first three images are in group 1, the second three are in group 2, and so on. 242 Index / Div +1 1 2 3 4 5 6 Group 1 1 1 2 2 2 This option would be suited for when all the observations are in one filter and you shot groups of three during the night, e.g., three images at 00:00, three at 00:15, etc. This option would force each group of three to become a single observation with the value being the average of the three. Read Filter Check this box to have PhotoRed automatically set the Filter radio group to the correct filter based on the FILTER key word in the FITS/SBIG header. It is critical that the correct “Filter” radio button is set to the filter used for the image being measured. Otherwise the reduction routines will be lead astray. It helps if the image names include the filter, as in the screen shot of the Image List. However, this may not always be the case and, depending on the way you've sorted the images for proper grouping, it may mean changing the Filter setting for each image before hitting the Accept button. This is definitely something prone to errors. If your imaging software includes the FILTER keyword in the FITS/SBIG header and the filter names are B(lue), V(isual), R(ed), I(nfrared), or C(lear), then the Image List can set the Filter selection for you automatically. If this is the case, then check this box before you double-click on the first image in the list to load it and start measuring. PhotoRed looks in the FITS/SBIG header and, if the FILTER keyword is found, attempts to interpret the value assigned to that key word to match. The first letter of the value must be B, V, R, I, C, g, r, i (case-sensitive) and those must correspond, respectively, to Blue, Visual (Green), Red, IR (Infrared), Clear, SDSS g’, SDSS r’, or SDSS i’. There are no provisions for using a different key word or for using “non-standard” names for the principle photometry filter names. You must assure that your imaging software follows these requirements for the FILTER key word. Filter Check the button of the filter used to take the image about to be measured. As noted above, the filter must be set correctly or the observations data will be wrong the reduction process meaningless. Using the example of the Image List screen shot at the beginning of this section, say you had the filter set to V and did not have the Read Filter box checked when you measured the first image, which as taken with the R filter. Go ahead and measure all the R images as V. When you get to the V images, set the filter to one of the other filters, but not V. After you're done, you can change the filter value of V to R and the alternate filter to V in the observation data which are displayed on the Reductions page. Photometry Wizards - The Transforms Wizard The Transforms Wizard allows you to specify which stars in a field are to be measured for finding transforms for either all-sky photometry or the QuickBinzel routine. By indicating an “anchor star” and recording the X/Y offset of all other stars from the anchor star, PhotoRed can measure any number of stars in just one pass. Once the stars are designated with the Transforms Wizard, you load the images to be measured in the List and measure the images. The process takes only a few minutes. 243 Transforms Wizard - Setting the Reason and Catalog Reason for Using the Wizard The pages that you see and what data are stored depend on which radio button you select. Extinction/Transforms Click this button if you’re using the wizard to measure a reference field for finding transforms or if you’re working with the Hardie method for first order extinctions. Quick Binzel Click this button if you’re measuring a target field that includes calibrated comparison stars and you’ll be using the Quick Binzel routine to measure the standard magnitude of the target in one or more filters. If have images in two or more standard filters, the Quick Binzel method will find the selected color index of the target. Select the Source for Magnitudes You have up to four choices for the catalog used to associate magnitudes with raw magnitudes. You can use one and only one for a given wizard session. LONEOS This option selects the LONEOS catalog. Use it when you know the field being measured has a significant number of LONEOS stars. User This option selects the User Star catalog. Use it when you know the field has a significant number of stars in the User Star catalog. MPOSC3 This option selects the MPOSC3 hybrid catalog based on 2MASS, SDSS, and Carlsberg catalogs. 244 Photometry Wizards - The Differential Photometry Wizard The Differential Photometry Wizard is almost an exact duplicate of the Lightcurve Wizard found in Canopus and it can be used for to measure either a moving or stationary target. When measuring asteroid images to get the color index, the motion of the asteroid may be enough that it moves out of range of the automatic placement of the measuring apertures. The most significant difference between this wizard and the one in Canopus is that once you start measuring images. This wizard can also be used if you worked a variable star mostly in Clear with a few sets of Clear/V (or R) images to establish a color index and first order extinction to use in the “Simple” reduction methods. This avoids having two sessions in Canopus with a limited number of C and V (or R) observations used for the reductions. Instead, the only session in Canopus will be the one with the main C observations for the program work. Users Guide Tutorials See the Users Guide for a tutorial using this Wizard. 245 246 Reduction Methods Most of the routines in PhotoRed are based directly on the algorithms used by Henden and Kaitchuck or A Practical Guide to Lightcurve Photometry and Analysis by B.D. Warner. The differential approach to standard magnitudes is based on a paper by Richard Miles in the Journal of the British Astronomical Association. Where possible, the data and results from those algorithms were used in Canopus to verify the correctness of the results. The following sections describe in some, but not necessarily complete, detail the theory and methodology behind the routines in PhotoRed. Detailed theory concerning transforms is left to the original sources. For a more thorough discussion see the book by Warner. Groups Say you want to get one or more V and R images for a field and treat them as if they were taken at the same time, e.g., you want to derive a V-R measurement for that moment. With a single camera, that’s not possible. PhotoRed somehow needs to know that the images are to be treated as if they were taken simultaneously. This is accomplished by assigning a group number to a set of images. In the example, the V and R images taken at approximately same time would have the same group number. When PhotoRed runs through its routines, it can group the images as if you had a multi-channel camera. Usually, you don’t take just one image through each filter. Instead you take two or three with the intent that the values be averaged. This reduces scatter in the data. Combined with the grouping just mentioned, PhotoRed can automatically do the averaging for you. For example, say you take a quick succession of three images in each of three filters of a standard field. In PhotoRed, you would assign the same group number to all nine images so that PhotoRed knew that the data for the nine images was to be “lumped together.” Then, when running through the routines, PhotoRed sums the magnitudes for each star in the three images for a given filter and uses the average value as the magnitude for that star in that filter for that group. It is not required that you have the same number of images for each filter, though having at least two helps reduce data scatter. Getting more than three images in each filter is probably not warranted in most cases. The concept of groups is an important one to understand when using PhotoRed. In the simplest terms, all observations of a given object in a given filter that have the same group number will be averaged to find a single magnitude for that filter and air mass value. Therefore, it makes little or no sense to put observations made many minutes or even hours apart into the same group. The Color Index (CI) Value For the V filter, the CI value is often B-V, i.e., the catalog B magnitude minus the catalog V value. However, in PhotoRed the solution can be based also on V-R, V-I, g’-r’, or r’-i’. Some of the routines specifically ask which catalog color index to use when running the calculations. Later on, when you run the routines that find the standard magnitudes of comparisons and target, you must tell PhotoRed which CI was used in the previous methods. It’s critical when you convert Canopus instrumental magnitudes to standard magnitudes that those observations used the same filter or filters that you used to determine the transforms and color index values for the comps and targets. For example, if you use V and R filter measurements of the target and reference fields in PhotoRed to establish the transforms and color indices, then the imported observations must be in V and R (C is also allowed if you do the transforms to convert C to a standard band). On the other hand, you can select any standard color index for the reduction steps, just as long as there are catalog values in the two colors and you use the same standard color index throughout all the reduction steps. For example, 247 as strange as it might sound, you can find the relationship between instrumental v-r and standard B-V and then use that relationship to complete the reductions to standard magnitudes. Regardless of the color index you use, keep in mind that to find the transform for a given color requires that there be catalog values for that color. For example, to find a transform for R, there must be R values in the catalog for the reference field(s) you shoot. As mentioned before, the C filter is treated as its own band but uses standard band magnitudes from the catalogs plus one other for transforms and CI determinations. In short, think of the C filter as a standard filter with a higher pass through but keep in mind that the reductions may not be as good in terms of matching the standard system as using a true filter for the selected band. First Order Extinctions and Transforms It’s important to understand that the PhotoRed implementation the FOE and Transforms routines are intertwined and it does matter which you one you do first – and it’s probably not the one you think. The Modified Hardie for FOE values method works by putting the raw instrumental magnitudes obtained when measuring two reference fields approximately onto a standard system. To do this, you must first find the transforms. That may sound backward to many since the FOE values are usually used to adjust the raw instrumental magnitudes before working out the transforms. Part of the normal process of finding transforms is to find what’s called the nightly zero point. These are the offsets that bring the final results of the reductions process into line. An examination of the formulae involved shows that on a first order evaluation, changing the assumed value for the FOE in a given filter has the affect of changing the nightly zero point value for that filter but it does not change the transform value. In other words, the slope of the line that equates the instrumental color to the true color of a star does not change even if an incorrect FOE value is used. The previous is a very important concept to understand and is vital to the PhotoRed methods. The FOE formulae for the Modified Hardie method apply the transforms against the catalog color index value for the star and use that to correct the instrumental magnitude of the star. The corrected instrumental magnitude is then used in the solution to find the FOE. Note that this means you need observations only in the given filter to find the FOE extinction values though you must have observations in two standard filters to find the transforms. These are in addition to C even if that is the only filter in which you’ll be imaging the target for the bulk of your work. How does this all tie together in PhotoRed? It means that you can use any reasonably placed field (say 45° or higher) to find the transforms using FOE values of 0 or something close to what you expect the final FOE values to be. Those transforms are then used to find the FOE values using the two reference fields. The beauty of the method is that the higher of those two reference fields, if it has a sufficiently different air mass from the second field, can be used for both reductions. The Modified Hardie Method for First Order Extinction The modified Hardie method for first order extinction is elegant and simple in approach and has several benefits. One being that after you get experience with the process, getting the images takes only a short amount of time, leaving you more time to work your targets. Another is that it avoids problems with changing conditions through the night (realize, of course, that you don’t want to be doing all-sky photometry unless conditions are stable). Finally, the some of the images you use for the Hardie method can be used for finding the transforms and nightly zero points, meaning no additional time is used to take images of a separate standard field. The comp star method has long been used but it is really effective only if you have nearly perfect conditions throughout the night. That’s very rare for an amateur site. There are methods you can use to average out values obtained over several nights but those individual values must still be reasonably close to reality. If at all possible, use the modified Hardie method. Once you start getting consistent results, you’ll find your transformed values also become more consistent and reliable. 248 Even if you find good FOE values with modified Hardie method at the start of a night, keep in mind that they can change during the night. Since FOE terms in the PhotoRed routines for finding standard magnitudes drop out, the only real reason for finding FOE values is to get the most accurate transforms and standard color index/comparison magnitudes. If you take the images for these routines at the same time as those for the modified Hardie method, then the FOE values like would not change enough to matter and your final reductions to standard magnitudes for the target can proceed without concern as to the FOE values changing. A General Outline for Finding FOE and Transforms Values After some practice, the following approach will take a minimum of time from your observing campaign while improving the quality of your work considerably. 1. Get images of the reference fields, one with an air mass near 2.0 (30° high) and one as near as possible to the zenith. You will need images in two standard filters (and C if you plan to use it). There must be standard catalog values for the filters for which you want to find transforms and use the modified Hardie method to find first order extinction. 2. Measure both sets of images in PhotoRed, putting all the measurements into a single data file, with all observations from one reference field given the same group number, e.g., 1, and those in the second field a different number, e.g., 2. 3. If necessary, enter assumed FOE values. From the table on page Error! Bookmark not defined. you can see that 0.0 may not be the best choice if the field is not very close to the zenith. Instead try 0.3 for B, 0.2 for V, and 0.15 for R. 4. Set the Use flag for the observations in the lower field (higher air mass) to FALSE and then run the transforms routine. Save the transforms when satisfied with the results. 5. Reset the FALSE flag to TRUE for all observations in the lower field. Do not change the flags for the observations in the higher field. 6. Run the Modified Hardie FOE routine. Save the results when satisfied. If you want to improve the transforms slightly, go back to step 4, which reruns the transforms method using only the stars in the higher field but with improved FOE values. This step is usually not required as the improvement is not significant. Users Guide Tutorials The discussions about the reduction methods that follow below do not go into detailed steps of how to setup and run each method. Instead, refer to the Users Guide where step-by-step tutorials are included. CI Means Color Index Instead of spelling out the possible combinations allowed under PhotoRed at every mention of color index, we’ll just say “color index” or CI from here on. Those allowed combinations are B-V, V-R, V-I, g’-r’, and r-‘i’. 249 250 Reductions: Transforms (Normal and 1-Filter) This routine uses raw instrumental magnitudes of stars in a single standard field and fits them into a linear regression solution using the catalog standard magnitudes to derive the values required to convert the instrumental magnitudes into standard magnitudes. The Henden and Kaitchuck book covers the theory behind deriving transforms in considerable detail and has excellent worked examples. In brief, for the V filter, one uses the general formula V – vo = a(CI) + ZP where V vo a CI ZP catalog V standard magnitude exoatmospheric magnitude transform value color index zero point offset Note that vo may or may not include first (and second) order extinction corrections. You can set the FOE values to zero, assumed values, or determine the nightly FOE values using the comparison star method. When you run this routine, you are asked which standard color index value to use. Make sure that there are catalog values for the two colors involved. This decision is independent of the filters that you use to make your observations. However, you must use the same color index throughout the reduction process. There must be catalog values for the filters for which you are finding transforms. For example, if you want to find the R transform, there must be R catalog magnitudes available. You cannot find the R transform using magnitudes from a different standard filter. The left-hand side is used as the Y-axis data and the CI value for the X-axis. When placed into a linear regression solution, the plot resembles the one shown above. This routine finds transforms for single colors and not color indices, e.g., it finds transforms for V and R, not V and V-R. This allows a more direct conversion to standard magnitudes when the bulk of observations are in one color. 251 The “Hidden” Transforms Part of the transforms reduction includes finding the relation between a given instrumental color index and the catalog color index values. This relationship is used in several other reduction methods, among them being the Quick Binzel, second order, and color index methods. The plot above shows the V-R versus v-r “hidden” transform for a particular system. With this transform, any instrumental v-r can be instantly converted into a V-R on the standard system. This transform comes in very handy in later routines since you can equate an instrumental to a standard color index and vice versa. 1-Filter Transforms This follows the exact same steps and can use the same data as the Transforms method. By selecting this option, PhotoRed bypasses the code to find the Hidden Transforms, even if you have the necessary data and select multiple filters. Remember that the transforms are found in terms of standard magnitudes, not instrumental, e.g., V-R and not v-r. As noted above, in some of the reduction routines where you have data in two filters, the instrumental difference is converted to the standard difference using the Hidden Transforms in order to plug the value into the transform to get the color-corrected standard magnitude of an object. However, if you know the standard magnitudes and color index beforehand, e.g., when doing AAVSO batch processing using AAVSO supplied photometry, then the Hidden Transforms are not needed. The same goes for finding the standard magnitude of a target. If you know the standard color indices of the comparisons and, better yet, also the catalog magnitudes, you can enter those directly into the Transforms form in PhotoRed and skip the steps required to find those. 252 Reductions: First Order - Hardie You must run the transforms method first, even if you must use assumed values for the FOE in each filter. Hardie explained this method in his section of Astronomical Techniques edited by W.A. Hiltner. It is particularly useful because it requires a minimum of time and effort to obtain the first order extinction values, leaving more time for observing the selected target. It also avoids problems due to changing conditions. The Hardie method relies on the difference between the actual measured magnitudes of two widely separated stars versus the difference in their true magnitudes. For example, if Star 1 and Star 2 differ by 1.0 magnitude in the catalog and differ by 1.2 in air mass, one would expect the difference in the measured magnitudes to be 1.0 (on the assumption that there is no extinction). However, the measured difference will not be 1.0 but a little more or less because of the air mass difference. Stated mathematically k’ = ((M1 - M2) - (m1 - m2)) / (X1 - X2) where M1 M2 m1 m2 X1 X2 catalog magnitude of Star 1 catalog magnitude of Star 2 measured magnitude of Star 1 measured magnitude of Star 2 air mass for Star 1 air mass for Star 2 The PhotoRed routine modifies this approach somewhat and also accounts for an assumption made in Hardie’s original paper. Specifically, that the instrumental magnitudes were on the standard color system. Naturally, raw uncorrected values measured from the images are not. In order to make that true, one must first find the transforms for the colors being used. These are applied to each raw instrumental magnitude – without any correction for extinction, of course, before being put into a linear regression solution. Lacking any atmospheric correction, the derived magnitude values in both fields would cluster around a constant value. Why? Say that a 10th magnitude star has a corrected instrumental magnitude of –10. In theory, a 9th magnitude star of exactly the same color (or adjusted to the same color by the transform), will have a transformed instrumental magnitude of –11 (remember that instrumental magnitudes are like the star magnitudes in that the brighter the star, the more negative the magnitude). The difference between these two pairs, -10/10 and –11/9, is 20. This is demonstrated in the plot above where the data points at each air mass are within a range of <0.1m. The introduction of extinction changes the constant value for each field, with the higher field’s constant difference being larger because the instrumental magnitudes are a bit brighter, i.e., more negative. 253 Using the averages of the derived values in each filed, PhotoRed finds the slope using a linear regression solution and the formula k’ = (Avg1 – Avg2) / (X1 – X2) where Avg1 and X1 represent the field with the higher air mass (lower altitude) Requirements for the Method 254 1. Conditions must be identical when you take the images to be measured, e.g., don’t shoot one or both in a thin haze. 2. The air mass difference should be as large as possible, at least 0.5 and preferably 0.7 to 1.0. This would mean shooting a reference field near the zenith and one about 30° above the horizon. 3. There must be catalog magnitudes in both fields for each filter used in this reduction method. This method can be used for Clear observations. In this case, catalog magnitudes are used in lieu of the nonexistent C band. Reductions: First Order - Comps This method uses the instrumental magnitudes and air mass values from Canopus-like data in a linear regression solution to find the extinction coefficients in magnitudes per unit of air mass. The data can be imported from Canopus using one or more sessions or by using the Differential photometry wizard in PhotoRed. The former makes sense if you did a long time series and measured images in Canopus. The latter works is you’re trying to get some quick FOE values from a few sets of images of the same field taken over a range of air masses. See “Getting and Measuring Images” for more details. All other considerations aside, a star gets brighter as it rises because its light travels a shorter distance through the atmosphere and so there is less absorption (extinction). This continues until the star reaches the meridian. After that, the star dims as gets lower and so its light goes through longer paths through the atmosphere. Photometric reductions can be based on the instrumental magnitude outside the earth’s atmosphere, i.e., exoatmospheric magnitudes. See “First Order Extinctions” for a look at when you might not need to worry about FOE values. The extinction value is applied via the simple formula mo = mi - k’X where mo mi k’ X exoatmospheric magnitude raw instrumental magnitude extinction value in magnitudes/air mass air mass at the time of the observation PhotoRed finds the value for k’ in each filter by plotting the raw instrumental magnitude of a comparison star for each observation versus the air mass at the time of the observation. The plot above shows an example of the results after running this routine. Of course, you must be sure that the comparison was not a variable; this can be accomplished very easily in Canopus. The biggest problem with this method is that it depends on the sky conditions being nearly identical throughout the night. If clouds or haze move in, they can cause the stars to dim artificially and so the solution is skewed. This is why the data is plotted. If there are “bad” data points, you can remove these from the calculations and get a better estimate of the true value. If, however, conditions slowly deteriorated through the night, the results are really useless. The comp star method is not the preferred method for those working in less than all-night all-sky photometric conditions. The value you find may not be the correct value because of changes during the night. Furthermore, that value may not be the one that was “in effect” at the time you took images of a standard field for finding the transforms and nightly zero points. This can skew your final results significantly. If at all possible, you should use the Modified Hardie method for first order extinction. 255 Reductions: Second Order Second order extinction accounts for the fact that all extinction is not created equal. Put simply, blue stars “fade faster” than red stars as they get near the horizon. By finding the second order term, you can correct the first order extinction based on color and air mass and so get the true extinction of the star. The principle behind the PhotoRed method for finding second order extinction comes from looking at the first order extinction for a number of stars of a wide range of colors (if you’re ahead of things, you’ll realize that the first order term found using the comp star method above includes first and second order extinction!). What you’ll see when using a B or C filter is that you get a different solution for different colored stars with red stars having a slightly less steep slope since they don’t fade as much at lower elevations. Why only B and C? By definition, the V and R filters are supposed to have zero second order terms. However, this is something you should confirm with your system. The same goes for the SDSS filters. Mathematically, what you’re finding is the “slope of the slopes”, i.e., a least squares solution using the slope of the first/second order extinction found versus the color index of the star. The value at X=0 (the Y-intercept) is the first order extinction and the slope is the second order extinction in units magnitudes per magnitude of color index per unit of air mass. The plot above shows such a solution using the SDSS g’ filter after following a red-blue pair over a range of 1.2 < X < 1.55. It would have been better to follow the field over a larger range and to use more stars in the solution, but this demonstrates the principle very nicely. For this system, the solution is about 0.02 mag per g’-r’ magnitude per air mass. 256 To be fully correct, one should be using the standard color indices of the stars but these may not be available. So, there is where the “Hidden Transforms” come into play. Those were available and so the instrumental color differences were converted to standard magnitudes at about half-way from the first and last observation so as to provide a reasonable average value. Reductions: Nightly Zero Points The Nightly Zero Points routine is used to find the zero point offsets that, when applied to the previously found transforms, minimize the errors between derived and catalog values in a reference field. If you find transforms and first order extinction on a given night, the NZP values are determine as part of that process and you would not run this routine. Instead, this routine is run on those nights where you want to do all-sky photometry and have already determined the system transforms. You can use either actual or reasonably-assumed values for first order extinction. Since FOE and NZP values are tightly integrated (see “Using PhotoRed - First Order Extinctions – Is This Trip Necessary” on page 232), holding one value constant allows finding a floating value that minimizes errors between derived and catalog values. General Steps for NZP Routine: 1. If necessary, load or confirm previously saved transforms values, i.e., the values found running the Transforms method. 2. Enter known or reasonably-assumed first order extinction values for the filter(s) that you will use for observations on the given night. 3. Take 3-5 images of a good reference field (Henden, Landolt) that includes catalog values for the filters in which you’ll be shooting your target fields. There must also be catalog values for the two filters used for the color index that was used when finding the transforms. For example, if you found transforms based on B-V catalog values, then the B and V magnitudes must be available for the stars in the chosen reference field. 4. Measure the images just as if you were going to determine transforms. 5. Run the Nightly Zero Point routine. 6. Save the results. The screen shot above shows the results of running the NZP routine. The first line gives the mean error (usually 0.000) and the standard deviation of the mean error, in magnitudes. The second line gives the original zero point for the given filter in question as well as the revised zero point value that produced the error. In this case, the NZP was about 0.013 mag larger than when the transforms were originally found. 257 Reduction Methods: Errors The errors routine allows you to check the transforms by converting the instrumental magnitude of each star in a standard field to a standard magnitudes and then subtracting the catalog value for the star, assuming the same band for both the instrumental and standard magnitude. In a perfect world, the mean error would be 0 and the standard deviation would be the same. However, there is always some random scatter in the data. This routine shows you just how much and if there might be a systematic error, e.g., the redder the star the greater the error in a given filter. 258 Reductions: Color Index (Comps/Target) In order for the differential reduction formulae to work in PhotoRed, you must know the standard, not instrumental, color index of the comparisons and target. The color differences between each comparison and the target factors into converting the raw instrumental magnitude in a given filter to the standard band. What’s handy about the PhotoRed approach is that you need only one to three images in each filter of the target field. If you have more than one image, PhotoRed averages the values of the set to generate a single value. You need a minimum of three to compute a true standard deviation. When you get those images depends on how you did the transforms, more specifically, if you used first order extinction terms in the reduction process. If you set the FOE values to zero, then the assumption was that the target field and the reference field were 1) close to one another and 2) that the fields were not too low to the horizon such that extinction differences were exaggerated by high air mass values. If the two fields are within 5° of one another and you shoot them when they are at least 45° high, the assumptions will be valid. If you used good assumed or actual FOE values, then the only requirement is that you not shoot the fields too low to the horizon and preferably higher than 45°. Another handy feature within PhotoRed is that you do not have to take and measure images in Canopus to find the color index values, as was required in early versions of the software. Doing that would leave a number of very small sessions used for a limited purpose. In PhotoRed, you can run one of two photometry wizards that produces data in the same style as if you had imported data from Canopus. If you did or will do a time series session in Canopus with the intent of importing the data for reduction to standard magnitudes, then you must be certain when measuring the images in PhotoRed for color index values that you use the exact set of comparisons. This means not only the same stars but in the same order, i.e., Comparison1 in Canopus must be Comparison1 in PhotoRed. Those doing limited work, e.g., keeping track of variables where precise photometry has not been done, can use this feature to find the color index of the comparisons and target so that they can used PhotoRed-only data to find the standard magnitudes for their targets. Again, it is no longer necessary to measure images in Canopus if your only purpose is to get just enough images to find the standard magnitude of a target and not worry about a prolonged time-series. 259 Reductions: Comps Standard Magnitudes The Comps Standard Magnitudes routine converts imported Canopus data into standard magnitudes. This routine can also work on data measured in PhotoRed. This is handy for those not doing extended time-series work but just getting standard magnitude values on some target fields, e.g., working a set of long period variables. You need observations in only filter for this routine. However, you must first get standard magnitude color index values for the comparisons. That routine requires observations in two standard filters but only a small number. The basic formula for converting instrumental magnitudes is M = mi - (k’m * X) + Tm * CI + Zm where M mi k’m X Tm CI Zm converted standard magnitude raw instrumental magnitude first order extinction air mass transform for the single color (not a color index transform) standard color index of the object zero point offset Note that the standard and not instrumental color index is used. That’s because PhotoRed is finding the standard magnitude in one color and the previously found transforms for this purpose were based on knowing the standard and not instrumental color index. This is a departure from the more traditional approach that finds transforms for all colors except V in terms of color index, e.g., B-V, by having instrumental values in B and V, i.e., b-v. The approach in PhotoRed eliminates the need of having observations in more than one color – assuming that either you find the standard color index values for the comparisons or provide them manually based on previous work. First Order Extinction Considerations Note that the first order extinction value is included in the formula. This allows for when you use an assumed or true value. It’s critical that the FOE values be the same that you used when finding the transforms. The reasons are given in “First Order Extinction and Transforms in PhotoRed” but, in short, the nightly zero points are affected by the FOE values. It can be shown that all other factors being the same, the only difference in the transform for a given filter with different values of FOE is to shift the nightly zero point. If you used 0 for the FOE values because the target and reference fields are close together, then you must use 0 when you run this routine, otherwise the reduced magnitudes will be wrong by the FOE value. Note that this does not include any second-order extinction terms. PhotoRed does not compute or use these. 260 Once the conversion is done, PhotoRed plots the values. Assuming you have at least two, preferably three measurements, PhotoRed also reports the standard deviation of the averaged values for each comparison. If you have only one observation, the s.d. is set to 99.999 since the s.d. in this case is undefined. Manually Entering Standard Magnitudes for Comparisons. It is not necessary to get images for or to run this routine if you know the standard color index values for the comparisons you’ll use in the target field. This might be the case for a variable star that’s part of an AAVSO observing program where sufficiently accurate photometry has been performed on set comparisons that every observer uses. In this case, select Photometry | Transform values to display the Transform Values form. Enter the values for the filters for which you ran the transforms routine and will be finding the standard magnitude of the target. This form will be discussed in more detail later. Enter 99.900 for any comparisons that you are not using. Do not enter 0 since PhotoRed considers this a “real” value corresponding to a very bright star. Roll up The Transforms form can take a lot of screen space and have to be moved around to work with the plots. So you can keep it open but out of the way, double-click on the title bar of the form to reduce it to just the title bar. Double-click the bar again to restore the form. The form is forced to normal height just before closing so that PhotoRed will display the full form when displayed again. 261 Reductions: Target Standard Magnitudes The Target Standard Magnitudes method is similar to the one for comparison stars save that the results are handled a bit differently. For one, the values are not stored in the Transforms form. Another is that in addition to the plots you see above, if the data were imported from a Canopus session, it can be exported out to files that can be used in Canopus for analysis or merging with other Canopus data. As with the comparisons routine, you need to have observations in only one filter but you must know the standard color index of the target before you run this routine. If the asteroid is a target, you should shoot three images in each filter in as short a time as possible. It’s best not to group images by filter when shooting but in sequence, e.g., VRVRVR and not VVVRRR. The reason is so that when you measure the images, you put the first V and R in group 1, the next V and R in group 2, and so on. This keeps the two different filter images close together in time. PhotoRed then finds the average for the three readings to provide the single color index value. Were you to shoot in VVVRRR fashion and the asteroid is changing magnitude quickly (as in the second plot above), then the color index value is affected. For example, if the asteroid is fading, then the average of the three R images will be dimmer more than it should be and so the result V-R greater than the real value. Why the two plots for the same routine? It depends on the data you provide. The first plot (partly covered with only one data point) was the result of measuring a target field in PhotoRed in order to get a single V reading for the target, i.e., there was no time-series involved. This might be the case if you’re working a set of variables and getting only one or very small number of readings per night. The second plot is the result of working with data that was imported from Canopus where a protracted time-series session was created to monitor an asteroid (an eclipsing variable star might have a similar curve). As an aside, note the vertical axis is divided into 0.05m steps. This was high quality data with errors generally <0.01m. The process for this routine follows these steps 1. PhotoRed finds the average value of the instrumental magnitudes for each comparison and the target within each group. 2. Using the transforms and standard color indices for the target and each comparison, PhotoRed uses the differential formula to find the reduced standard differential magnitude of the target based on one comparison at a time. Mf = (TIavg – CIxavg) + Tf * (CIT – CIxc) Where Mf TIavg CIxavg Tf CIt CIxc 262 differential standard magnitude in filter f average of target instrumental magnitudes average of comparison X instrumental magnitudes transform for filter f standard color index of target standard color index of the comparison X 3. The reduced standard differential value is then added to the previously determined standard magnitude for the comparison in question to find a reduced standard magnitude for the target. In a perfect world, the reduced standard magnitude would be the same for each comparison/target pair. 4. The average and standard deviation of the reduced target standard magnitudes are found. It’s important to appreciate what’s going on in steps 2-4. Say five comparisons are used. One way to find the target’s standard magnitude might be to find the average of the reduced standard magnitudes of the comparisons and simply subtract that from the reduced standard magnitude of the target. That would work if all the comparisons and target were exactly the same color. Since there are very likely color differences, the standard color index for each comparison and the target must be used to get the best possible standard magnitude for the target. To do that without the differential approach would require having observations in two standard filters. Instead, using the transforms based on one-color observations and known standard color indices, a reduced differential standard magnitude of the target versus a comparison is found for each comparison. The differential value is then added to the standard magnitude for the given comparison, which eventually yields five reduced standard magnitudes for the target. Step 4 finds the average of those reduced magnitudes to derive a single value and computes the standard deviation of the average. In addition to the plots, the standard magnitudes are saved into a text file that can be viewed on the Std. Mags table of the form (see screen shots above). Here’s a representative sample: ***************************** JD = JD - 2400000.0 ***************************** CLEAR ----J.D. Mag. ---------------------53475.60718 12.133 53475.60910 12.147 53475.61101 12.146 53475.61293 12.087 53475.61484 12.104 ... VISUAL ----J.D. Mag. ---------------------53475.60728 12.138 53475.60920 12.144 53475.61111 12.148 53475.61303 12.082 53475.61494 12.104 The file can be saved by clicking the Save button the on the Std. Mags tab. 263 264 Reductions: AAVSO Batch Processing In late 2007, the AAVSO implemented a new reporting format for CCD observations. PhotoRed has been modified to meet the requirements of the new method and to better conform to the approach used by most AAVSO observers. However, the new format introduced some new ways of looking at old concepts, particularly when talking about ensemble photometry, so you need to keep an open mind and not assume what has been is what is. In the simplest approach, it is not required that you get transforms or determine nightly extinction values. In this case, the data would be reported as NOT TRANSFORMED. If, however, you determine or know the color index values of the comps and targets and have found the basic transforms for your system, then you can include these corrections in the data and would report the data as TRANSFORMED. With only a little time and care, reporting transformed values can significantly improve the accuracy of your work, so you should consider finding the transforms for your system. The QuickMags routines and data table formerly used for AAVSO observations are no longer used. There is no routine to convert the QuickMags data to the new AAVSO tables. The data storage requirements to comply with the new AAVSO standards are substantially different. The AAVSO Format – Beware the Check Star The full AAVSO format document is available on the AAVSO web site. In short, here are some highlights and how PhotoRed works within the new guidelines. 1. Ensemble photometry is allowed. To do so requires that there be a “check” star whose magnitude is presumably known. The definition of a check star for this purpose differs from the old one for a check star. Before, and under the new format when not claiming ENSEMBLE photometry, the check star magnitude was subtracted from the comparison star magnitude for each observation. The trend of those values should have been a straight line, indicating that neither star was variable. The definition of a check star when doing ensemble photometry is that it is “second target” but of known and constant magnitude. It is treated like the target in that the one or more comparison stars are used to find a derived magnitude for the check star for each observation. This derived magnitude is reported along with the derived magnitude of the target. In a perfect world, the values for the check star would be identical for each observation and would exactly match the true magnitude of the star. Since this will not likely be true, the difference between the derived magnitude for the check star and its accepted (catalog magnitude) can be computed and that difference applied to the target’s derived magnitude to get its “true” magnitude. PhotoRed always uses ENSEMBLE photometry, even if using one comparison and one “check” star. This is not a user-settable option. Therefore, you must always have at least one comp, one and only one check star, and one and only one target in each Batch Reference File (see below). 2. The AAVSO format is a character-delimited file, i.e., each line in the simple text file is an observation with the “fields” being separated by one of three characters. The default is the pipe symbol, |, since this cannot be easily confused with the comma as being part of a field or a delimiter. 3. The application of transforms is allowed. This is a user-settable option available at the time you measure the images. 4. The format allows for DIFFERENTIAL (offsets from the comp magnitude) or ABSOLTUE (reduced to “true” magnitude). The AAVSO strongly encourages ABSOLUTE. PhotoRed forces ABSOLUTE. This is not a user-settable option. The Process Outline The general steps to go from collecting photons to generating a report are: 265 1. Take images in at least one standard filter of the target during an entire session. If the color index of the target and comps are not known, then you should take images in a second standard filter that would form a common color index, e.g., V and R, B and V, etc. a. If you have not determined the transforms for your system and plan to apply them, you must take images in two standard filters of a Landolt (preferably) or Henden field. You would use these images to find the transforms using the methods in PhotoRed. b. You do not have to find the nightly zero points and extinction every night. The AAVSO reduction method uses extinction, but it is a common value for all observations in a given filter and so it, along with the nightly zero point, drop out of the solution. If you are observing in two or more standard filters, what is important is that you have first order extinction values that form reasonable differences for a given color index. For example, if using V and R, the extinction value should be such that k’v – k’r ~ +0.05. You should determine that this is a good value for your location and system but it will serve in most cases. 2. Before measuring any images you create a “Batch Reference File” (BRF). This process is required only once for a given target field unless you change the comparisons and/or the standard magnitudes for the comps and check stars and/or the color indices for the comps, check, and target. In short, the batch reference file provides the RA/Dec and magnitudes for the comps, check, and target. PhotoRed uses AutoMatch and the data from the BRF to determine the location of the stars and target on each image and automatically measure them. 3. Once you create the Batch Reference File (BRF), make sure you have loaded the transforms for the system you are using (if you are going to include them) and set the measuring apertures as needed. Those having only one scope/camera will not have to worry about recalling saved transforms. Those who observe using multiple setups must find transforms for each system, save those results, and recall them when measuring images. 4. Run the Batch Differential Photometry form. This form allows you to create a number of “batch definitions”, each with its own batch reference file and list of images. The entire set of batch definitions can be saved in a single file. So, for example, if you regularly observe 20 LPVs every week, you can create a single file that will process the images for all 20 stars and place the data in the data tables. With some planning, you never have to change the entries in the set and can use it for as long as nothing changes. After the data are in the data tables (AAVSO.FF2 and AAVSO2.FF2), you can generate AAVSO compatible reports, do batch editing, and export the data to Canopus SESS/OBS file pairs. When imported into Canopus, the latter allow you to do period searches and to generate Binary Maker 3 files for modeling. 266 The Batch Reference File Generator The purpose of a Batch Reference File Generator (the Generator) is to tell PhotoRed the location (in RA/Declination) of the target, check, and comparisons. You must also provide at least one standard band magnitude for each comparison and check star (the same band for all). If you are going to reduce the observations, i.e., include corrections for color index, you must provide the color index for each comparison and check and the target as well. You must create a separate file for each target/comps set. Assuming you have included the necessary data, you can use the same reference file more than once, i.e., when measuring images for the same object/comps but in different filters. In the example above, where B and V magnitudes are available, this one BRF can be used to reduce observations in B and V. During batch processing, PhotoRed opens a reference file and does an astrometric solution on each image to be measured. This solution is then used along with the RA/Dec in the reference file to find the target and comps and then measure the magnitude of each one. Users Guide Tutorial The Users Guide contains an extensive tutorial on AAVSO batch processing, covering the Generator, the Batch form to measure images, and generating AAVSO reports. The following sections provide additional information and details on entry fields on the forms. See the Users Guide to understand how to put the forms and methods to use. The Batch Reference File The Batch Reference File (BRF) is a simple text file with a specific format. You can create it by opening an image in PhotoRed, matching it to one of several catalogs, and selecting the stars and target by clicking on the image. You can also create it via a parsing program of your own that writes the data from another source to the expected format. Finally, you can import data from the AAVSO Variable Star Plotter directly and so have “official” data immediately available. If you create batch reference files outside PhotoRed, you should at least load some random examples and confirm that PhotoRed can read them and confirms the formatting. Data Entry Fields If getting data from a catalog, many of these fields will be automatically entered when you click the Get button. If necessary, you can change the values before you add the set to the references list. The advantage of working with an image and catalog is that, if nothing else, the RA and Declination are entered for you. Star Source If using an image to retrieve information, select the catalog from which data is taken when you click on a star and then click the Get button. 267 Import Button This allows you to import data directly from AAVSO star chart photometry. See the tutorial in the Users Guide and “Importing Directly from AAVSO Photometry Tables” on page 270. Get Button If you’re using an image to retrieve information, click this button to fill the data entry fields with the information for the selected catalog. If getting magnitudes from a catalog, make sure you check the appropriate color index radio button before clicking Get. If the magnitudes for the selected color index are available, the color index value is automatically computed and entered when you click Get. Add Button Click this to add the data in the entry fields as an item in the reference list. Edit Button Click this to replace the information of the highlighted item with the values in the data entry fields. Delete Button Click this button to delete the highlighted item in the references list. Type Select the type for the item to be added (or when changing the type of an exiting item). Comp Comparison star. There must be a least one comparison in each reference list. Check Check star (as defined for ENSEMBLE photometry (see pg 265). There must be exactly one check star in every batch reference file. Target The target to be measured. There must be exactly one target in every batch reference file. Name Enter the name of the item. If available, use the AUID (AAVSO Unique Identifier) or other accepted AAVSO identifier. If you click the Get button, the catalog name will be placed here. You can edit the entry before you add the data to the reference list. RA Enter the RA in hh:mm:ss.ss format. Use leading zeros as needed. If you use the Get button, this and the Declination field are automatically entered. The entry control’s mask accepts only 0-9. You do not have to enter the delimiter characters, colon or period. Dec Enter the Declination in ±dd:mm:ss.s format. Use leading zeros as needed. The sign (+ or –) is mandatory. The entry control’s mask accepts only 0-9. You do not have to enter the delimiter characters, colon or period. B/V/R/I/g’/r’/i’ Enter the standard magnitude for the given filter. If there is no magnitude, enter 99.999. Do NOT enter 0.000, since this will be interpreted as a very bright star. If you use the Get button to retrieve data from a catalog, those magnitudes that are in the catalog are automatically entered. CI Enter the color index value for the color index selected by the Color Index radio buttons. If you are not going to use transforms, no color index is required and you should enter 99.999. Color Index Select the color index to be used, if any, when reducing the data. 268 If getting data from a catalog using the Get button, make sure this button is set before you click the Get button. If the magnitudes of the selected color index are in the catalog, the CI data field value is automatically computed and entered based on this selection. Group The AAVSO format allows grouping data so that it can be used to compute a color index. For example, you can set the group number for a B observation and V observation to the same number and, in addition to recording the B and V magnitudes, the B-V magnitude will be computed and stored in the AAVSO database. Group -1 Meaning No grouping. No group number will be included in the observations. 0 A group number will be allocated dynamically, with the first image measured being assigned 1, the second 2, and so on. That group number will be included in the AAVSO report. >0 Every image will be assigned the value in the Group field. That group number will be included in the AAVSO report. Quoting from the AAVSO documentation for the CCD reporting format: GROUP is a special value. It is used for grouping multiple observations together, usually an observation set that was taken through multiple filters. Then the database software can retrieve all magnitudes from a given set and form color indices such as (B-V). If you are just doing time series, or using the same filter for multiple stars, etc., just set GROUP to 'na' [PhotoRed does this automatically when you set Group to -1]. For cases where you want to group observations, GROUP should be integer, identical for all observations in a group, and unique for a given observer for a given star on a given Julian Date. An example may help. Say you have a set of BV images taking in rotating succession all night on a given variable, i.e., BVBVBVBV.... You would like the AAVSO database to have not only BV magnitudes but B-V as well. If you set the group to 0 and use this batch reference files to measure those images, then each observation in each filter will be assigned an automatically incrementing group number, starting with 1. When the AAVSO system reads the data, it will see a B and V observation with group = 1, compute the B-V magnitude, and add that to the database. It will do the same for group 2, and every group beyond. Load Click this button to load a previously saved batch reference file. Save Click this button to save the current batch reference file. The data are checked to make sure that certain rules are met, e.g., exactly one check and exactly one target, at least one comparison, and that the RA/Declination are valid for all items. See the Users Guide for a tutorial on creating a Batch Reference File using an AutoMatched Image. Creating a BRF without Opening an Image It may seem a daunting task to go through this process if one is working dozens or hundreds of entries. If you have access to the necessary data such that you can create a BRF without working with an image, that is perfectly acceptable. The BRF file is a simple comma-delimited text file. Each line represents one item, i.e., the check star, a comparison, or the target. There must be exactly ten “fields” for each line with each field’s value surrounded by double quotes and the fields separated by a comma. "TARGET","V432 PER","-1","03:10:10.82","+42:52:08.9","11.380","10.900","99.999","99.999","0.439" "COMP","P198-C","-1","03:09:32.30","+42:58:37.0","11.990","11.080","10.594","99.990","0.488" "CHECK","P198-D","-1","03:09:24.80","+42:57:49.0","12.620","11.460","10.860","99.990","0.600" "COMP","P198-G","-1","03:09:09.30","+42:57:32.0","14.599","13.150","12.393","99.990","0.757" 269 Importing Directly from AAVSO Photometry Tables If the field you are working is an AAVSO target star for which there is photometry available on comparison stars that you’ll use for your observations, you can save a considerable amount of time by importing the AAVSO photometry directly. Charts and photometry data are available from the AAVSO site at http://www.aavso.org/observing/charts/vsp/ You must save the file as HTML or, at the least, the file must contain the original HTML code. Do not save the page as a simple text file with the HTML code removed. The Users Guide contains a tutorial on downloading and importing chart data from the AAVSO site. Defining and Running a Batch Process The Batch Differential Photometry form (BDPF) is used to create a batch definition set (BDS) that is saved in a Batch Definition File (BDF). Each set consists of one or more batch definitions. In turn, a batch definition includes basic information unique to a given target, i.e., the reference file that includes the positions and magnitudes of the target, check, and comps, and the images to be measured. Once you have defined a batch definition set, you can save the data to a Batch Definition File (BDF). If you plan ahead, i.e., always put the images to be measured in the same working directory and give them the same names each time you do an imaging run, the one file can be used indefinitely. While the example above processes images for the same target in two filters, you could create a batch definition set that includes many targets using one or more filters. For example, you may have a program that measures a number of long period variables (LPVs) once a week. If you work it so that the images to be measured are always the same location, you can use this one Batch Definition File to measure the weekly images indefinitely, even if you change the contents of one of the batch reference files (but not the name or location). Loading and Editing a Batch Definition Set Click the Load button to load a previously saved batch definition set. If you need to edit an existing batch definition, highlight the definition in the list and then click the Edit button. To delete a batch definition, highlight it in the list and click the Delete button. 270 Adding a Batch Definition If you're measuring the same target in more than one filter, you must create a separate batch definition for each filter. For example, if you have images in B, V, and R to measure, you will have three batch definitions for the one star. On the other hand, unless you use different comparisons and/or check star for each filter, you can use a single batch reference file (BRF) for all three batch definitions. Name Enter the name for the given definition. This is not the name of the target. AAVSO The AAVSO designation (this is the value entered in the AAVSO tables for the name of the target). Chart Enter the chart used. If using the Variable Star Plotter on the AAVSO site, this is the date you created the chart. It appears on the chart in yymmdd format. If using older charts, use the chart reference that appears on the chart. Notes Enter any notes for the comment field. You can enter up to 100 characters, the maximum allowed by the AAVSO format. In the example above, the note indicates the magnitudes came from a sequence that were generated by a user named “Warner” using PhotoRed. If you use data from a Henden or LONEOS catalog, indicate that here. This value is stored with each observation. Filter Select the filter used for the observations used in this definition, i.e., B, V, R, I, or CV, CR, SG, SR, SI. CV means Clear filter converted to (using) V magnitudes. CR means Clear filter converted to (using) R magnitudes. SG, SR, and SI are, respectively, the Sloan (SDSS) g’, r’, and i’ filters Ref. File Use the button to the right of the field to locate the Batch Reference File (BRF) used to find and measure the target, check, and comparisons. Images To add images, click the “Add” button under the images list. This presents a dialog box that gives you the option of selecting all files in a selected directory. Individual Files If you elect to pick individual files, a file open dialog appears. After specifying the files, they are listed in the Images list. Directory If you opt to use all files in a given directory, a select directory form appears. After you select the directory, the entry includes the path to the directory followed by *.* (see the screen shot below). Do not change the name from *.*. PhotoRed looks for this in any file name and, if found, presumes the entry is a directory and not a file. In either case, select files or a directory where the images were taken with the selected filter and for the given target/comps set on a single Julian Date. 271 Processing Tip: Use Directories By selecting directories instead of individual images, you gain the full benefit of the Batch form. Presuming that the only thing that changes for a given batch definition is the set of files to process, if you keep the file list “generic”, then you do not have to change anything as you measure images from a given night. Go back to the example where you work a set of long-period variables every week or so. Create a work directory for each star to which you copy just the new images from each run and specify that directory in the batch definition. You can run the same batch definition set every time without changes. Move the images to a permanent location after you do the processing and wait until the next run. If you use this approach, keep in mind that you’ll need a separate directory for each star and filter combination. You don’t want to have V and R images in the same directory since the Batch form will presume they are all V or R. If you don’t follow a naming/working convention such that the location of the files is the same every time, then you will have to edit the definition, clear the list, and fill it with the correct set of images to measure before each processing run. Defining General Batch Processing Options Before you run the batch process, you need to tell PhotoRed how to compute the final results. Use Transforms Check this box to include color index corrections based on the values in the reference file and previously found color transforms using PhotoRed. Make sure that you have valid transforms for each filter that is included in the definitions. The actual values for the colors in the color index of choice don’t necessarily have to be exactly right but the differential value should be as close to realistic as possible, e.g., the first order extinction terms for V and R can be a good estimate but more important is that k’vr is ~ +0.05 (or whatever is appropriate for your system and location). Running a Batch Process Once you have one or more data sets defined, click the Process button to start. The status bar at the bottom will keep you updated on what's going on. Buttons and controls are disabled (though not always grayed) while processing and you cannot close the form. If you need to stop processing, click the Abort button. It may take a few seconds before processing stops. When the processing is done, the status bar says “Done” and the AAVSO Reporting form should appear. If not, click the AAVSO Report button. 272 See the Users Guide for a tutorial on creating and running a batch process. The AAVSO Report Form This form is used to view, batch edit/delete, and generate reports. Observed Stars Tab This tab provides a quick report that details which stars are in the AAVSO table, the dates of observation, number of observations on a given date, and the total number of observations for each star. Auto-generate Check this box to have the report generated automatically as the form appears. If you have a large number of observations, this can take several seconds. It’s better not to check this box and use the Make List button on demand. Make List Click this button to generate the list. Save List Click this button to save the report to a text file. Observations Tab 273 This tab shows you all the observations that fit the filter set on the Batch Edit tab. If no filter is set, all observations are available. You cannot edit observations on this tab. You can delete individual observations and search for observations by the name of the target. The read-only memo field at upper right shows the contents of the Comments field that is included in an AAVSO report. The second table shows the secondary data in AAVSO2, which includes data on the CHECK star required for ensemble photometry and reporting as well as details on the comp stars. Batch Edit/Delete/Archive Tab This tab allows you to batch edit some fields in records, delete a set of records, and archive/restore data so that the primary AAVSO and AAVSO2 tables do not become unwieldy. It is strongly recommended that you make a backup of AAVSO.FF2 and AAVSO2.FF2 before doing any batch editing. Name Enter the name of a given star. If this field is blank, all records matching the other filter elements are included. Start Enter the first date of the range for records to be included. The entry must be in yyyy/mm/dd format and use leading zeros if necessary, e.g., 2009/02/10 for February 10, 2009. The assumed UT is 00:00. End Enter the last date (00:00 UT) in the range. The entry must be in yyyy/mm//dd format and use leading zeros if necessary. A common mistake when filtering will be to set the date range incorrectly. For example, if you want to see the data for October 20, 2007, you would set the Start to 2007/10/20 and the End to 2007/10/21. If you use the same date for Start and End, then no records will be included, unless there happens to be an observation at exactly 0h UT on 2007/10/20. Filter Use the drop down list to filter the results set by filter. Use “All” to include all records that otherwise match the record filter. 274 View Check this box to activate the filter. You must set a filter before you can batch edit or delete records. Batch Editing Once you set the filter, enter the values you want to change. These include the name of the object, the name of the check star (e.g., to enter the AUID instead of a catalog name), the chart ID, a comment code, and up to 100 characters for the comment field. Batch editing replaces existing entries. If, for example, you want to add to the comment field, you must enter the entire comment you want, not just the additional information. Click the Edit button to edit all records matching the filter. Batch Editing – Changes The fields in this section replace existing data in the related fields. Obj Name Enter the name that will replace the records specified by the Name filter. You cannot batch edit records with a new Obj Name without specifying a filter that includes a specific name and date range. Otherwise, you’d be able to change all records to be of the same star. Check (K) Name Enter the new name for the check star. Chart Enter the revised chart name. The AAVSO charts from the Variable Star Plotter are given a specific name when you generate the chart (or photometry data). If you update data based on a new chart, you would use this field to specify the new chart (data’s) ID. Comment Code Use the drop down list to change the comment code for the selected records. The list of options is taken from the AAVSO documentation. Notes or Comments Enter a note or comment (up to 100 characters) that will replace the existing Notes field for each selected record. Convert C Obs The AAVSO does not accept “just C” observations. The filter must be specified as CV (clear, using V magnitudes) or CR (clear, using R magnitudes). If you have records with the filter set to “C”, this allows you to change the filter to something the AAVSO accepts. Apply Click this button to apply the changes. Batch Edit – Update Mags The Update Mags feature allows you to modify the stored catalog magnitudes for the comparison stars, the color indices for the target, check, and comparisons, and then recalculate the derived magnitude for the target with or without using transforms. This is a useful feature should the AAVSO update its photometry tables for the target or you use PhotoRed to calculate improved values for a field where you established your own photometry sequence. 275 The Update Magnitudes Form Click the “Update Mags” button on the Batch Edit page to display the Update Mags form. Name Enter the name of the target for which changes are to be made. You must specify a name before you can update magnitudes. Start Enter the start date (00:00 UT) for the range of data to change. The format is yyyy/mm/dd using leading zeros if necessary, e.g., 2009/09/24 for September 24, 2009. End Enter the end date (00:00 UT) for the range of data to change. The format is yyyy/mm/dd using leading zeros if necessary. A common mistake when filtering will be to set the date range incorrectly. For example, if you want to see the data for October 20, 2010, you would set the Start to 2007/10/20 and the End to 2010/10/21. If you use the same date for Start and End, then no records will be included, unless there happens to be an observation at exactly 0h UT on 2010/10/20. Validate Magnitudes Check this box to have PhotoRed confirm that the magnitudes and color indices were the same for all records that meet the search parameters. If any of the values changed, an error message is displayed, and the process stops. Locate Click this button to find records that match the search parameters. If the search is successful, the Value/Mag table is filled with the values from the records. Value/Mag Table The Value/Mag table displays the value names and values for the check, target, and comparison stars. You cannot edit the names but you can change the values. Enter updated magnitudes in the Mag column. The table will accept non-numeric data, i.e., letters or symbols other than the decimal separator. If such characters are found when you apply the changes, an error message is displayed and the process stops. 276 Use 99.999 if there is no magnitude value available. Do not enter 0.000 for a catalog magnitude. PhotoRed will interpret that to be a very bright star. Enter 0.000 for the color index if that is not known. Update Magnitudes Form – Updating Catalog Magnitudes After you have reviewed and confirmed the values for all items in the Value/Mag table, click the “Mags/CI” button. This displays a confirmation message. Click “Yes” to apply the changes. Update Magnitudes Form – Updating Target and Check Derived Magnitudes Once you have confirmed the catalog values for the target, check, and comparison stars, you can also update the derived magnitudes for the target and check star. You have the option of applying transforms during this process, specifically, correcting the instrumental magnitudes for first order extinction and correcting for the color differences in between each comparison and the target and check stars. This is also handy should you have generated the data before you determined the transforms and want to apply them “after the fact” and before you submit the data to the AAVSO. Use Transforms Check this box to apply the transforms stored and shown in the PhotoRed Transforms form. Recalc Click this button to apply the new catalog values and transforms to the existing instrumental magnitudes to find new derived magnitudes for the Target and Check star. Batch Delete Set the filter (enter data in the fields and check the View box). You will receive two warnings preceded by beeps since batch delete means that deleted records cannot be recovered, unless you restore a backup. Archiving AAVSO Data The two main files, AAVSO.FF2 and AAVSO2.FF2 can get very large very quickly if you’re doing extended time series work on many variables. The archiving process allows you to export records based on a combination of name and range of dates. Once you have archived those records, you can delete them from the main files. You can view the data later by loading the exported files. An example of using the archiving feature would be to remove all the observations in a given month so that you have only the last three months of data in the main AAVSO tables. If you do this monthly, the main tables will stay a manageable size and you’ll have the original data (saved in a safe place – right?). If you have the configuration set to do so, the AAVSO and AAVSO2 tables are backed up each time you close Canopus. This provides an additional archiving mechanism. Exporting Data If you want to export data for only one object, enter the name of that object in the Name field. Then enter a range of dates that will include all observations that you want to export. Remember that the dates are for 0h UT. If you set the Start and End to the same date, no records will be exported, unless there happens to be an observation at exactly 0h UT. Once the filter is set (use the View check box to confirm the filter), click the Export button. The data are exported to two files \MPO\UDATA\AAVSO_<Start>_<End>.FF2 \MPO\UDATA\AAVSO2_<Start>_<End>.FF2 277 Where the Start and End values correspond to the Start and End date entry fields in yymmdd format. Maximum File Name Length The export process gives the output files long names so that you have a clear indication of what’s in the file. However, those file names will likely exceed the 32-character limit for file names as dictated by the database engine. Before you attempt to import the files for review or generating reports, make a copy of the two files and rename them to shorter names, e.g., AAVSO_TEMP.FF2 and AAVSO2_TEMP.FF2. If you want to change the names, be sure to keep the AAVSO_ and AAVSO2_ at the beginning of the file and the FF2 extension. The rest of the name after AAVSO_ or AAVSO2_ must be identical for both files or PhotoRed will not be able to reload them. Loading Exported Files Click the Load button to load exported files. The file open dialog will show only the AAVSO_*.FF2 files, meaning that there must be a corresponding AAVSO2_*.FF2 file. Once you select a file, the data in the two tables temporarily replaces the data in the main AAVSO tables, i.e., you will see only the exported data. You will be able to generate reports as you normally do. Do not use the archive function when you are viewing exported data. Restoring the Main AAVSO Tables Click the Clear button to restore the main AAVSO tables after loading exported files. Clicking this button when the main tables are active causes no harm. AAVSO Reporting Tab This tab is used to generate reports compatible with the new AAVSO format for CCD observations. The Users Guide has a tutorial on generating a report for submitting to the AAVSO Name Enter the name of the object for which data are to be included in the report. If no name is specified, all objects otherwise meeting the search parameters are included. If this field is not blank, the “Output Options” radio group is enabled. 278 Start Enter the start date, in yyyy/mm/dd format, for the first date for data to be included in the report (the time is forced to 00:00 UT). End Enter the end data, in yyyy/mmdd format, for the last date for data to be included in the report (the time is forced to 00:00 UT). A common mistake when filtering will be to set the date range incorrectly. For example, if you want to see the data for October 20, 2007, you would set the Start to 2007/10/20 and the End to 2007/10/21. If you use the same date for Start and End, then no records will be included, unless there happens to be an observation at exactly 0h UT on 2007/10/20. Observer Code Enter your AAVSO-assigned observer code. If you don’t have a code, apply for one before submitting reports. There is no charge and you do not have to be a member of the AAVSO to get the code. Delim Chose the symbol that separates the fields in the report (see the example below). The default is the pipe symbol ( | ) since there is usually no confusion if it’s part of the data, as is the case sometimes with the comma. The choices are the semicolon ( ; ), comma ( , ), and pipe ( | ). Filter Boxes Check one or more filter boxes. These restrict the report to those observations for which its box is checked. SG, SR, and SI are the Sloan (SDSS) g’, r’, and i’ filters, respectively. C is for “Clear” filter. The AAVSO does not accept observations with “just C”. You should be using CV (clear, using V magnitudes) or CR (clear, using R magnitudes). If you have records with only “C” for the filter, use the batch edit page to convert those records to have CV or CR. Output Options Select one of the two options for outputting data for a specific star. All Include all matching records Every X Obs Include every Xth observation, with X the value in the “X” field. This option is handy if you make dozens or even hundreds of observations of a given target and want to limit the number that are submitted to the AAVSO. The data are not binned when using the “Every X Obs” option. Literally, every Xth observation is used. Generate Click this button to generate the file. Once the report is generated, a file save form appears. You can accept the default name and location or change one or both and then save the file. This file can be sent as an attachment to an email to the AAVSO or uploaded on their site. It’s strongly recommended that you send the file as an attachment if emailing the AAVSO. Otherwise, your mail program may word wrap the lines and cause all sorts of problems. A portion of a typical report appears below. See the AAVSO documentation for an explanation of the keywords and format. #TYPE=EXTENDED #OBSCODE=WAB #SOFTWARE=MPO CANOPUS/PHOTORED v9.4.0.0 #DELIM=, #DATE=JD #NAME,DATE,MAG,MERR,FILT,TRANS,MTYPE,CNAME,CMAG,KNAME,KMAG,AMASS,GROUP,CHART,NOTES 279 AH TAU,2454399.788299,11.105,0.013,V,YES,ABS,ENSEMBLE,na,2UCAC40638709,11.736,1.096,na,071026, AH TAU,2454399.790636,11.119,0.036,V,YES,ABS,ENSEMBLE,na,2UCAC40638709,11.752,1.091,na,071026, AH TAU,2454399.793717,11.100,0.020,V,YES,ABS,ENSEMBLE,na,2UCAC40638709,11.744,1.085,na,071026, Do not edit this file unless you are absolutely certain you know what you’re doing and why. The format is very specific as are the use of the keywords in the header. Changing any of those may cause the data to be rejected or, at least corrupted, when received by the AAVSO. Extended Reports Tab This tab generates an extended report, similar in format to the AAVSO standard but including the data on the check and comp stars. It also exports data to Canopus export set files. These can be imported into Canopus for period analysis and plotting. The Extended report settings in the “Filter and Fixed Data – Extended Report” section are the same as for the AAVSO standard report. The Users Guide has a tutorial on creating Canopus export set files. Canopus Export Name Enter the name for the object for which data are to be exported. This field cannot be blank. Start Enter the UT date and time for the start of data to be exported. The date format is yyyy/mm/dd using leading zeros if necessary. The time is 24-hour format, also using leading zeros if required. End Enter the UT date and time for the end of data to be exported. The date format is yyyy/mm/dd using leading zeros if necessary. The time is 24-hour format, also using leading zeros if required. Filter Boxes Check one or more filters. A separate When generating Canopus export files, the date range must be less than 24 hours and you must specify a single target, i.e., you cannot export data for all targets within a given date range. This is in keeping with the concept of sessions in Canopus where a session contains data on a single target on a single night using the same set of comparisons stars. However, you can select more than one filter. A separate SESS/OBS pair is generated for each filter. 280 If you create export and then import data files for Canopus, be sure to set the Photometry Method to “Transformed” and “Absolute” for the plot method. This is the only way you will see an accurate representation of the data. If you use Instrumental, the data will not include any transform corrections. Generate Click this button to generate the output file. All data are put into a single export set pair with the base name being the name of the object followed by an auto-increment number and then the mandatory endings. For example, if creating the first export set for AB AND, then the two files will be AB_AND_1_SESS.FF2 AB_AND_1_OBS.FF2. 281 282 FITS Keywords The FITS/SBIG header editor in the MPO programs does not allow user-defined keywords to be added or edited. In addition, it forces the data type for each allowed keyword and a picture (entry) mask when editing or adding data for the keyword. Any data being edited or added must fit the associated entry mask. See the notes at the end of the list for the meaning of entry mask characters. The keywords are the most common from the FITS/SBIG standards. Keyword AIRMASS APTAREA APTDIA BITPIX BSCALE BZERO CBLACK CCD-TEMP CDELT1 CENTALT CENTAZ COMMENT CWHITE DATAMAX DATAVERSION DATE DATE-OBS EGAIN EXPOSURE EXPTIME FILEVERSION FILTER FOCALLEN HEIGHT HISTORY IMAGEDEC IMAGERA IMAGETYP INSTRUME NAXIS NAXIS1 NAXIS2 OBJCTDEC OBJCTRA OBJECT Mask ii.iii 9999.99 9999.99 iii 9999.9999 99999.9999 iiiii iii.ii iiiii.iii ±DD MM SS.s ±DDD MM SS.s X iiiii iiiii X yyyy-mm-dd yyyy-mm-ddTHH:MM:SS.sss iii.ii 99999.99 99999.99 X X 99999.999 iiiii X ±DD MM SS.ss HH MM SS.sss X X iiiii iiiii iiiii ±DD MM SS.ss HH MM SS.sss X Type Float Float Float Integer Float Float Integer Float Float String String String Integer String String String String Float Float Float String String Float Integer String String String String String Integer Integer Integer String String String Len 6 7 7 3 9 10 5 6 9 11 12 70 5 5 5 10 23 6 8 8 5 70 8 5 70 12 12 70 70 5 5 5 12 12 70 283 OBSERVER ORIGIN PEDESTAL SBMODIFY SBSTDVER SETTEMP SIMPLE SITELAT SITELONG SNAPSHOT SWCREATE TELESCOP TEMPERAT TEMPREG TIME TIME-OBS TIMEOFFSET TRAKTIME UT WIDTH XBINNING XORGSUBF X_PIXEL_SIZE XPIXSZ YBINNING YORGSUBF Y_PIXEL_SIZE YPIXSZ X X iiiii X X iii.11 B ±DD MM SS.ss DDD MM SS.ss iiii X X iii.ii B HH MM SS.sss HH MM SS.sss iiiii.iii iiiii.ii HH MM SS.sss iiiii ii iiiii 9.9999 99.99 ii iiiii 9.9999 99.99 String String Integer String String Float Boolean String String Integer String String Float String String String Float Float String Integer Float Integer Float Float Float Integer Float Float 70 70 5 70 70 6 1 12 12 4 70 70 6 1 12 12 9 8 12 5 2 5 6 5 2 5 6 5 Picture Mask Characters Character Allowed Entry Character B T or F i +, –, or 0 through 9 9 0 through 9 X Any character yyyy Four-digit year mm Two-digit month. Use leading zero if necessary dd Two-digit data. Use leading zero if necessary. ± + or – required HH MM SS.sss 24-hour time. Use leading zeros if necessary. For example: 05 23 54.220 284 ±DD MM SS.ss Use leading zeros if necessary. For example: ±25 32 45.12 . (period) Decimal character must be entered at this location. For example: if the mask is iii.ii, you can enter –23.2, 23.43, but you cannot enter 23.445. The ‘T’ in the DATE-OBS mask is a literal character, i.e., you cannot enter it directly and it is always forced to be within the data string. The DATE keyword can be ambiguous in format. The FITS standard allows for it to use the same format as the DATE-OBS format. However, the SBIG header uses the mm/dd/yy format with the USER_4 keyword defining the “epoch” so that the two-digit year can be properly converted to a four-digit year. 285 286
