Good results using Intermediate Calibration spreadsheet
It's been a while, but over Thanksgiving weekend I decided to try out the intermediate spreadsheet and take some images of the Epsilon Aur area to see how it would match up. After crunching all the numbers and looking at the results, I'm very happy with the precision I seem to be getting. Many thanks for creating the spreadsheet which made the process a LOT less time consuming than if I had to do it myself.
To obtain magnitude measurements, I used my modified Canon XT camera and a 50mm lens. Each measurement has a series of 5 star images (with flat frames and dark frames), aligned and stacked. The camera was out of focus enough so that each star covered about 15-20 pixels in diameter. For each measurement series, I calculated an Extinction and Transformation Coefficient. I took the images at a time when all the stars measured had an airmass of 1.2-1.3
I'm attaching a spreadsheet which summarizes my results so far. I do have a couple of questions though:
- My extinction coefficient varied by quite a lot (-0.03 to -0.259). All images were taken within a few minutes of each other, so I was not expecting the such a wide range. My average ended up as -0.116 with a standard deviation of 0.072. Does this seem normal?
-After all my results, I am wondering about the listed magnitude for Omega Aur. All of my other check stars come within 0.01 magnitude or less of the published value. My average result for Omega Aur differed by 0.023. Granted that's still pretty close, but I've see a couple of other sources that give the magnitude of Omega Aur as 4.93 or 4.94 (a better match to my results) rather than 4.95. Has anyone else had a similar experience? SIMBAD gives a V magnitude for this star as 4.989 and also mentions an 8th magnitude companion, so I wonder if adding the two together are causing different results?