Hi Grant,
Yes, fitting à la DAOPHOT, then deriving differential magnitudes via linear regression fit to an ensemble obtained from a VizieR catalog. You can select the catalog you need. The result shouldn’t be very much different from DAOPHOT, albeit I’m using its implementation in Astropy’s photutils. So, MetroPSF is a convenient GUI to photutils with some add-ons like linear regression fitting, plate solving, source matching, etc.
You click on the source you’d like to measure in the window. Here is a short write-up on functionality, check the Quick Start section here:
http://trafyx.com/wp-content/uploads/2021/04/metropsf-3.pdf
Near-saturation are not ignored, but you can choose Gaussian sigma weighting for the ensemble, so PSF fits with high sigmas which generally appear with oversaturated sources, will be assigned less weight in the fit. Would you recommend to introduce “hard cut-off” for oversaturated stars?
Max
P.S. Grant, thinking this over again, an obvious manual solution to avoid oversaturation is to limit source magnitudes in the ensemble, which is possible in MetroPSF already. This can be combined with sigma weighting as well.