TrES-3b - First Observation

posted Nov 4, 2013, 2:38 PM by University Astrophysics Club   [ updated Nov 4, 2013, 2:43 PM ]
This was our first observation using the Faulkes telescope and would have gone well had the pesky weather not acted up. As such we were only able to observe for about 45 minutes, effectively capturing about half of the transit that we were attempting and none of the pretty pictures.

Despite that, however, I think getting together was a success. We started the night with some brief information on Faulkes itself as well as a (very) brief overview of exoplanets and how we go about detecting them. We then went over the Faulkes simulator tutorial so that we could begin promptly trying to capture the transit. Our observation time began at 19:00 HST and the transit was set to ingress at 19:10, so it was important we capture as much as we could as soon as the telescope opened up. Cameron took the controls and did a great job of staying on top of the button pushing. Since we weren't changing any settings in between observations, it would be nice to be able to say we want X amount of images at these settings and then not have to worry about it, but as is we just need to keep watching for when one exposure is done and then hit 'Make Observation' over again.

We had a little initial confusion over the amount of time it would take and we were counting on getting 156 images at 30-second exposure in the ~80 minutes of transit. However, we had forgotten that it takes 2*exposure time to capture an image (just as long to move off CCD as to put on CCD) so we ended up with effectively half of that.

So, after eating some pizza and hanging around hoping the weather would turn, we decided to try and generate the light curve with the FITS images that were available to us. LCOGT.net provides the following SalsaJ tutorial, so we gathered in the astronomy lab and went through the steps on the projector. Essentially, this boils down to getting the light intensity for our target star and some comparison stars and then entering them into a provided spreadsheet. Again, since we were running through the tutorial for the first time, there was some confusion about how to set the Star's Radius and Sky Radius, so we ended up just using the 'Auto' feature provided by SalsaJ. This turned out to be a a not-so-great idea and in follow-ups we did manually set the radii so they were consistent across all images and photometric readings. Also, it turns out the spreadsheet is just taking Target Intensity / Comparison Intensity but recommends using the average of a couple of different comparison stars, which was also done in the follow-ups. 

But, in the end, we have half a light curve, as seen on the right (these were generated from the follow-up, so they include the proper radii and three different comparison stars). For the sake of a pretty graph and full light curve, we took the highly unscientific method of doubling and reversing our data, which gives us the full light curve seen in the Extrapolated graph. Check out the spreadsheet for the values and the calculations (Extrapolated Data is on the second sheet).
We have a number of observation dates set throughout November and will be trying to capture the transit of KOI 1459-b, which is an unconfirmed exoplanet. For those observations we will be doing a more official write-up which will include how we went about selecting filters, exposure times, and overall methods as well as the follow up science to all those fun FITS files.

Thanks to Cameron, Callie, Alex, André, Derek, Ethan, Krystal and Wilfred for showing up!

~ Astro





Actual Data

Extrapolated Light curve


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