second order extinction

Posted by rrgem on Mar 14, 2017; 11:22am
URL: http://astroimagej.170.s1.nabble.com/second-order-extinction-tp634.html

Dear Karen
we are teaching broad-band photometry (B, V, R, I) to high school students and we would like to use your wonderful software not only for exoplanets but also for pulsating variable stars. We have a couple of question for you. In order to obtain accurate absolute magnitude of the target, what about atmospheric extinction (especially second order extinction)?
The second question relates to overall error estimation. At the end of data processing we obtain something like: Source_AMag_T1 =12.486 ; Source_AMag_Err_T1 = 0.003
but our standard stars have an associated error between 0.018 and 0.055
How we can resolv this problem and producing a final uncertainty measurement with contributions from both the uncertainties of the stellar magnitudes and those of the ADU measurements on the images?
Thank you so much
Marta