On the growth-curve method for calibrating stellar photometry with CCDs

Abstract

Stellar photometry with CCDs usually relies on the construction of aperture growth curves for its ultimate calibration. In the past this has been a tedious chore requiring a great deal of human intervention, mostly to select data suitable for defining empirical growth curves from data sets containing some corrupt values. A computer program has been written which incorporates a priori knowledge of the typical morphology of stellar profiles and is capable of taking a synoptic overview of all the aperture growth curves from an entire night or observing run. The program is thus enabled to make its own judgments as to the reliability of individual data points and to draw physically reasonable growth curves without human supervision, even for individual frames with insufficient or badly contaminated data. The program runs quickly and independently and produces results not noticeably inferior to those obtained by traditional hand-and-eye methods.