In this study, we captured 21 images of the star GSC 03089-00929 and used these images to form two tables and two graphs. We completed this by knowing basic information for TrES-3b, involving the coordinates, time of transit, and the best possible location to capture an image of the transit. The coordinates are organized with right ascension (R.A.) and declination (Dec.). The coordinates of TrES-3b are, in decimal form,
, which points towards the constellation of Hercules, which is only visible in the Northern sky (Hercules)(Sky and Telescope). This is good to know because that narrows the telescopes that are possible. The time of transit was determined by going to Itelescope.net, finding a telescope that would work, and determining its coordinates on Earth. The telescope that was used was t24, which is a deep field telescope, allowing the viewers to see dimmer stars. By clicking on the link for t24, the coordinates can be found. There are many websites that can predict the time of transit for a specific area of Earth. Jefflcoughlin.com is the website that was used to find the time of transit. The transit that was used in this study started around 9:15 UT and ended around 10:45 (Coughlin). In order to capture, analyze, and visualize the results of an image series, the team used Itelescope.net, Aavso.org, and Excel 2003. At Itelescope.net, the telescope that was required was found, labelled t24. The weather was checked to make sure that the images could be taken without any interruption or distortion from the sky. The telescope happened to be vacant at the time of use, which was convenient because only one user may capture an image at a time. Once the telescope was determined to have a clear field of view, the link to t24 was clicked. On the left, there was a link, under ‘Imaging’, titled ‘Run Image Series’. That link was clicked. Once on this page, the team had to fill out the boxes that required information, such as the target name, R.A., and Declination. The target was TrES-3b; therefore, that’s what was inserted there. Underneath those, there was a series of blanks and check boxes. For each type of image the team wanted taken, there needed to be a new row for it. The count boxes stood referred to the amount of images of that specific filter, duration, and binning that the telescope would produce. The team’s input was as shown in Figure 1. Once all the boxes are filled out correctly, the button near the bottom of the page, titled ‘Acquire Images’, was pushed, leading to the telescope starting up. Once the telescope receives the instructions for the image series, the team clicked on the link on the left, underneath ‘Toolbox’, which was titled ‘System Status’. From that page, the team could watch the telescope and watch what it was doing. This part was very important because if the telescope stopped taking images, the team needed to know why and what went wrong with the telescope. The telescope would send out information to this page to constantly update the team about what was going on and how the images were being taken. Once the program finished, the program emailed all 21 of the images to the users email.
The team downloaded the images from the email that they received and placed them somewhere easy to access on their computer. In order to transfer the images to vPhot, they used a program called CoreFTP. This program was used to remove the images from the computer and to move them to the AAVSO server that way they were uploaded to the vPhot server. In order to do this, the team needed to find the vPhot server address, which was given to them by their mentor. The server title and address can be found online.
Once the upload to the vPhot server was complete, the images could then be accessed on vPhot. To get there, the team searched for AAVSO on any web browser. Once they got to the website Aavso.org, they scrolled all the down to the bottom of the page. At the bottom, underneath the title ‘Data’, was VPHOT-Online Photometry Tool. This link was clicked to bring the team to a page that had another link to vPhot, once which was clicked, they arrived at vPhot. At vPhot, there were many images that could be viewed but there weren’t the images that the team put there. They had to go to the filter settings and adjust the title of the image they are looking for, the filter type, and the time uploaded. Once that was all done, all 21 images showed up in chronological order.
In order to calculate the magnitude, the team had to locate the star and eliminate any other variable stars that were there. GSC 03089-00929 shows up as a variable star because the transit of TrES-3b raises the magnitude. The team clicked on the first image because it was the first image taken. Once the image loaded, the team went to the drop box labelled ‘Catalogs’. Under here, they clicked ‘Load AAVSO Comp Stars’ and ‘Variable Star Index GCVS’. This loaded stars in the image that have a known, unchanging magnitude and any stars in the image that are classified as variable stars. Once all of the stars were loaded, the team went to the top left of the page where there was a list of the displayed stars. They removed all of the variable stars (Green) that weren’t TrES-3. TrES-3 is another name for the star GSC 03089-00929. Then the team did two separate things, leading to two different procedures. The first was the removal of all other stars except for the star labelled 130. Once that was done, the team needed to alter the annulus around TrES-3. If the smallest circle around the star didn’t have the entire star within it, then the annulus needed to be altered. This was done by going to drop box labelled ‘Tools’ and clicking ‘Aperture and Sky Annulus’. Once clicked, a box popped up that allowed for the adjustment of all of the circles. Once the innermost circle was all the way around TrES-3b, the team made sure that they only had the stars TrES-3 and 130 in the higher left display box. Once this was done, the team clicked a button titled ‘View Photometry Report’. Once this was clicked, the magnitude (Mag) and error (Err) were recorded. This was only done if the error was below .025, which it was. The team then pressed the link ‘Back to Image’, this brought them back to the image. The entire process was repeated except that instead of having the star 130, they keep the stars 130 and 139. This helped the team collect more data with the same image. This process was repeated for every image (Mogul).
Once the magnitudes and errors were recorded for every single image, the team began work on the graphs and tables. Using Excel 2003, the team created two separate tables that represented their data. Using the tables, they also made graphs based on the measurements. There was one graph per table. When creating the graphs, the team flipped the x-axis to allow to help visualize the decrease in brightness that was found.