Posted 23 December 2013 - 01:17 PM
I was interested in how a C filter, combined with g' and r', could allow an estimate of M. It turns out it works pretty well.
All the stars in ucac4 have a magnitude value, but only some of them have g' and r'. If I calibrate with g', r' and c using g', r' and m values - I have a lot of info - and error bars on the estimates.
I'm not driven by a use-case here - I'm mainly driven by an interest in getting a feel for the errors and uncertainties in doing photometry - particularly with Sloan filters in 2013, where UCAC4 happens to be convenient. I assume standards will change over the next years and I hope u'g'r'i'z' remains relevant - but who knows.
For me, the uncertainties with 8" sct and 5x10s exposures in the 10-13M range appear to be limited by the standards used for calibration rather than the errors in my measurements. That was one of the things I set out to understand. I therefore don't need to spend time improving my flats or something.