Instrument Science Report WFPC2 96-03:
Background Subtraction in WFPC2 Frames
Henry C. Ferguson
June 05, 1996
Accurate photometry with the WFPC2 depends in part on accurate determination of the background level. This is complicated by the presence of cosmic rays and hot pixels, and by the discrete sampling of the input signal by the analog-to-digital converter. The purpose of this note is to estimate the rough errors on typical point source photometry introduced by standard methods of background fitting in IRAF, and to identify practical strategies for dealing with the background with existing IRAF software.