Download Using a DSLR to Detect a Known Exoplanet

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Using a DSLR to Detect a
Known Exoplanet
The equipment, tools, and processes needed -
Brent Maynard
[email protected]
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What are exoplanets?
 Exoplanets are planets that have been discovered outside of
our own solar system.
 There are almost 1800 known exoplanets as of June, 2014.
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Types of exoplanets
 The first exoplanets discovered were Jupiter class planets,
large gas giants.
 More recently, using new technology, multiple earth-like
planets have been discovered.
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Techniques used to discover an
exoplanet
 There are several techniques used in discovering an
exoplanet.
 The two most common are measuring the radial velocity of
the host star relative to earth, and transit photometry.
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Radial velocity technique
 As a planet orbits around their host star, the star will wobble
back and forth. Subtle changes in the star’s red-shift can be
detected, confirming the presence of an exoplanet.
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Transit photometry technique
 The transit photometry technique detects the transit of a
planet orbiting a host star, by measuring a decrease in the
stars brightness, as a planet transits the star as seen from
earth.
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Can we detect a known exoplanet
using basic equipment and tools?
 The answer is yes.
 Using a DSLR, telephoto lens, a tracking mount, and some
photometry software, we can detect an exoplanet transit
using the Transit Photometry method.
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What is Photometry?
 Photometry is a technique used in astronomy measuring the
flux, or intensity of an astronomical object's electromagnetic
radiation.
 For exoplanet detection, we are measuring the dip in the
amount of light received by the camera sensor.
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DSLR setup
 Because the dip in the amount of light received is very small,
we need to capture data at a resolution that can be
processed to verify a transit event took place.
 Therefore, we must capture the images as RAW images from
the camera, we cannot use JPG images to perform the
photometric analysis.
 We also don’t want to capture the images at a high ISO
setting to raise the noise level too high that could interfere
with the image data.
 Iso800 has worked well for my attempts.
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DSLR Raw image format vs JPG:
First the cmos/ccd Bayer Matrix
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DSLR Raw image format vs JPG:
First the cmos/ccd Bayer Matrix
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DSLR Raw image format vs JPG:
First the cmos/ccd Bayer Matrix
DSLRs typically save their Raw image files in 12 or 14 bit
images
If you have your DSLR set to take JPG images, they are saved
in 8 bit images.
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DSLR Raw image format vs JPG:
First the cmos/ccd Bayer Matrix
When the DSLR takes a picture, and you have it set to JPG, the
processor inside the camera will convert the Raw image into a
JPG and then toss the Raw data.
At 8 bits, each pixel has 2^8 levels of brightness.
2^8 is 256.
In Raw mode, current DSLRs save images as 14 bit images,
2^14 is 16,384 levels of brightness for each pixel.
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How do we know which stars have
exoplanets?
 The Exoplanet Transit Database
 http://var2.astro.cz/ETD/predictions.php
 My first attempt – HD189733b using Canon T3i and a
300mm telephoto lens.
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HD189733b
 Is a fairly bright star, short transit duration, large (relative) dip
in the light curve, and easy to find in the sky.
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HD189733b
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HD189733b
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Second attempt HAT-P-3b
 Very challenging, dim star. Was not sure I had detected the
transit of the exoplanet until I processed the data 8 times.
 I used a 180mm telephoto lens for this transit attempt.
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Photometric Software
 IRIS – Free astronomy software, very powerful image
processing software, but is not real user friendly.
 Spreadsheet software, Excel or Numbers to make the
graphs.
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IRIS process
 http://www.astrosurf.com/buil/us/iris/iris.htm
 Set working directory in IRIS
 Decode the RAW files
 Register (align) the images
 Perform photometric analysis using 1 target star and 4
reference stars
 Save photometry data for curve plotting
 Choose different reference stars to confirm results.
 Process reference star to also confirm transit detected.
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Questions