The PSF modeling tasks conveniently create and set flags indicating which sources were used to determine the PSF model. The single-frame astrometric and photometric calibration tasks should do the same, indicating at least (for each procedure):
- Which sources were selected for potential matching.
- Which sources were actually matched.
- Which sources were actually used for calibration.
As we have done in PSF modeling, it would also be good to have the ability to reserve a set of candidate sources for validation purposes.