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Transcript
Northern Prairie Star Party
Black Nugget Lake
September 15, 2012
Brian Martin
The King’s University College
Three Fundamental “Sciences”
• Measuring “Distance”, Position & “Scale” 
Astrometry
• Measuring Brightness and Intensity 
Photometry
• Measuring “Colour”  Spectroscopy
Exciting science that you can do from the
back yard!
Astrometry
How big are the lunar
features in this image?
August 29, 2012
H-alpha filter
0.001 s exposure
ED80
Atik 314L+ camera
TKUCO
Some Math …
R
S
q
*
The Small Angle Formula Rq
= S where:
• R = distance from object
• q = angle that the object subtends in the sky
• S = distance across the object
* Angle in radians
The Scale of Your Telescope
• Scale in (seconds of arc)/mm found by:
206,265
scale 
focal length
• In the previous image a ED80 telescope was
used so the scale is (206265)/(600 mm) =
343.8 “/mm
• The Atik 314L+ has 6.45 mm pixels, so each
pixel has a scale of
342.8”/mm × 0.00645mm/px = 2.22 “/px
when used with the ED80
• By measuring the number of pixels you can
measure the angle that an object or feature
subtends
s  rq
s  (0.002524 AU)(149 598 000 km/AU)
2.2 "/ px
206265"
Distance = 0.002524 AU
s  4.027 km / px
304 px = 1236 km
850 px = 3457 km
(0.5% error)
Some other images…
• Capuanus Crater:
–
–
–
–
–
–
December 26,2009
C14, f/11
Imaging source DMK2104
2000 frames
Distance = 0.002523 AU
Scale = 0.20”/px = 0.37 km/px
• Apennines (Eratsothenes, Archimedes)
–
–
–
–
–
–
March 1, 2012
C14, f/7
Atik 314L+
20 frames (0.005 s)
Scale = 0.52”/px
Distance = 0.00262 AU
• Jupiter
–
–
–
–
–
–
November 5, 2011
Distance = 3.98101 AU
C14, f/11
Imaging Source DMK2104
LRGB (~2000 frames each)
Scale = 0.29”/px =
837 km/px
159 px = 133 000 km
170 px =
142 000 km
Oblateness = (142 -133)/142 = 6.3%
• M57
–
–
–
–
–
–
August 26, 2011
C14 f/7
ST7E
LRGB
Distance = 2300 ly
Scale 1.49”/px =
0.017 ly/px
160 px = 2.7 ly
• M15
–
–
–
–
–
–
August 21, 2011
C14 f/7
ST7E
LRGB
Distance = 33 Kly
Scale 1.49”/px =
0.238 ly/px
534 px = 127 ly
Photometry – Measuring Changes
in Brightness
• Intrinsic Variables
– d Scuti
– SX Phe
• Novae and Supernovae
• Cataclysmic Variables
Consumer grade CCD cameras…
•
•
•
•
•
•
Capable of doing excellent science!
Modest cost (< $2000)
Excellent software support
Monochrome with no anti-blooming is
preferred
Pixel size should be carefully matched
to image scale – need to oversample
Capable of milli-magnitude precision
photometry
Atik 314L+
SBIG ST7E
SX Phoenicis Variables
• BL Camelopardalis
– Average mag 13.1
– Period
• 0.0389d
• 56 minutes – this is
an exciting system
to watch!!
40 s integration, C14 f/7
ST7E camera – KAF400 detector
The Light-Curve…
BL Cam
Teff 7730 K
Age ~4Ga
Metal poor
Period shows a
Small change
over time!
November 9, 2009
November 9, 2009, s (C2-C1) = 0.007 mag
DY Pegasi … A Nice Intro to SX Phe
• A great star!
– Bright (m = 10.3)
– Excellent Check and
Comparison stars
– Well placed for fall
observations
Data collected with 8” Newtonian and
SpectraSource Lynxx (TC211)
Cataclysmic Variable Stars
• Binary stars that are
exchanging mass
• One of the stars is compact
• Hot spot forms on accetion
disk
• Accretion disk around
compact star produces
variability
• A rewarding study for
amateurs!
Two exemplar CVs…
• DW Uma
– Period (d) 0.136606
– Mag 14 - 18
TKUCO 120 s image 0.32 f/4.8
• GK Persei
– Period (d) 1.996803 d
– Mag 11.5 - ?
TKUCO 60 s image 0.32 f/4.8
Other Photometric Delights!
• Novae and Supernovae
• Algol systems
• Asteroids
NGC 6946
30s exposure
September 29, 2004
SN 2004ET
0.32 f/4.8 Newtonian
ST7E camera
Spectroscopy
• Broad and Narrow band filter imaging
• Low Resolution Spectroscopy
• Medium – High Resolution Spectroscopy
Broadband Colour Imaging
L
R
M27 LRGB, August 2011, C14 f/7
ST7E
G
B
Narrow Band Imaging
•
•
•
•
Ha
Hb
SII
OIII
Ha
S II
O III
C14 f/7
Atik 314L+
March 1, 2012
LRGB image of central region of
M51 C14 f/7 ST7E
L filter with Ha overlay showing star
forming regions along spiral arms
C14 f/7 Atik 314L+
Stellar Spectra (Low R)
• Remarkably easy to do – even with modest
equipment!
– Small telescope w/wo tracking
– CCD or DSLR
– Rainbow Optics or Star Analyzer grating
• Introduces a fascinating new direction for
amateurs
Some samples…
(trailed images with Atik 314L+, Orion 80 mm ED)
Note Deneb’s narrow lines!
Vega, Teff = 9600 K
Altair, Teff = 6900 K – 8500 K
Ca II line
Altair is a very fast rotator and
is squished like a football!
Hotter at the poles by about
20%
Other Interesting Stars…
Which is these is the
hottest star?
T = 7 100 K
F2
T = 31 000 K
B0.5e
T = 8 400 K
A5
Be Star with disk
Planetary Nebulae
The “Eskimo” – NGC 2392
C14 f/7 10 minutes
April 21, 2011
The reason nebula
filters work!
Measuring the Expansion of the
Universe!
Rest Frame
(A)
Measured
(A)
Dl
(A)
z
Hb
4860
5666
806
0.166
Ha
6563
7562
990
0.151
z
Dl
3C273 C14 f/7 60 minutes
ST7E April 5, 2011
l
Zaverage = 0.159
Universal Expansion
• What does z = 0.159 mean?
–
–
–
–
Apparent recessional velocity is 0.159C = 47 700 km/s!
Hubble expansion law: v  HR
Hubble’s constant H = 70 km/s/Mpc
R = 681 Mpc = 2.2 billion light years!
Medium/High Resolution
Spectroscopy
• For more advanced work
• Requires robust mount and
tracking
• Need as much aperture as
possible
• BUT – still well within the
reach of advanced amateurs
and astronomy clubs!
The L200 Littrow Configuration
• Can resolve to about 1 A (R = 3000)
• Built from a kit, cost ~$1000
• Capable of useful research on Be, WR and
Algol type stars (and much more!)
The Solar Spectrum
ST7E on C14
Altair
Homebrew for under $200!
And it Works!
The Magnesium Triplet…
R > 5000!
Some References…
• Christian Buil http://www.astrosurf.com/buil/
• Tom Field - RealTimeSpectroscopy (RSPEC)
http://www.rspec-astro.com
• Rainbow Optics Spectroscopes
http://www.starspectroscope.com/
• Center for Backyard Astrophysics (CBA)
http://cbastro.org/
Thank you – Questions?