...
- repair CRs
- background estimation
- how well does it work near bright stars, big galaxies, crowded fields
- star selector
- initial PSF (FWHM)
- general PSF determination
- astrometric matching
- astrometric/WCS fitter
- photometric calibration
- aperture correction (measureApCorr)
- (there's detection/measurement in this part as well)
...