DAOPHOT

DAOPHOT is a software package to assist in carrying out photometry using CCDs. It was initially developed in late 1980s, with the goal of extracting photometric data of individual stars from CCD image data of crowded fields. It effectively carries out sky subtraction, determined which set of pixels constitute the data for each star, untangling some somewhat-overlapping Airy disks, and individually summing the photon counts of each star. DAOPHOT II is a name for a circa 1990s update, though the software generally still goes by DAOPHOT. DAO stands for Dominion Astrophysical Observatory (Vancouver, Canada) where it was developed, and PHOT is for photometry.