Using Standard Fields to assess CMOS photometry.

British Astronomical Association, Variable Star Section (BAA-VSS)
Sat, 11/18/2023 - 15:57

Is there a set technique for assessing my photometry using the Standard Fields?

I have practised using one to measure transformation coefficients using Transformation Generator (TG)

E.G. Should I set say half of the stars as comps and the other half as targets?

I would be using VPhot.

Variable Stars South (VSS)
Use photometric standards

I'm not the best quaified observer to answer this question, but no-one else has answered in more than two days. In principle, I use photometric standard stars in pairs, one assigned as the target and the other as the comp star. Do this for a number of pairs.  You can then see how accurate your photometry is.


Variable Stars South (VSS)
Look at precision as well


My post was too abrupt. You probably know this, but at the same time you can assess your precision simply by taking multiple exposures (e.g., 10 or more) all of the same exposure duration of your test field, and performing photometry on the same photometric standards in each image. The standard deviation of each magnitude measurement provides an indication of your precision.

I find it useful to plot such results (mag on the y axis against frame number or JD on the x axis) with the y axis range being several tenths of a magnitude. If you do this regularly, you will soon get to know, for your setup, what a good set of precise measurements looks like. For photometry on variable stars, the light curve of the check star will do the same sort of thing for you.


American Association of Variable Star Observers (AAVSO)
Colored or monochrome CMOS


Are you using monochrome or OSC/colored CMOS? Just wondering about the equipment you're using.