Numerous tickets bemoan the flaws of PsfCandidate:
Based on the comments on those tickets, and a review of the existing code, propose a redesign or update to address these flaws.
Geometrically check that PsfCandidates are sufficiently far from edge
makePsfCandidate needs to be easier and safer to use
Stars selected by starSelector change when number of cores varies
LengthError in making psfCandidate
making PSF candidates should be simpler