How to test digital camera photometry precision?
I am a longtime visual variable star observer and try to make my first contributions in photometry with Epsilon Aurigae.
For this I acquired a cheap used Canon Powershot G3 which is not a DSLR but able to take raw images. My procedure is
to take 6-10 raw images, average them in AIP4WIN, extract green image and measure with the Single Image Photometry Tool.
I always use "bracketing" using a brighter comparison star (Eta Aur) and a fainter one (58 Per).
So far this resulted in quite satisfactory results, my measures agree within a few hundreths of a magnitude with each other
and the V values in AAVSO quick look. It looks like I am able to do better with the camera than as a visual observer.
Some questions arise:
* is there a way to test precision of my measures?
* how to improve precision? The camera takes a dark image after every 15 second image which is the longest I am able to expose. Also
I cannot defocus, I simply use autofocus for this
* how to plot the "TG" (tricolor green) measures I reported to AAVSO in the light curve generator?
I appreciate pointers and ideas!