Instrument Science Report WFPC2 96-04:
Effects of Contamination on WFPC2 Photometry
Brad Whitmore, Inge Heyer, and Sylvia Baggett
June 14, 1996
Photometric monitoring observations are examined to determine the effect of contamination on WFPC2 photometry. New contamination rates are determined using observations of both a white dwarf standard (GRW+70D5824) and a globular cluster (Omega Cen = NGC 5139). Evidence for a long term increase in throughput with time has been found on the PC1 for F160BW and F170W filter observations. This, and other supporting evidence from the thermal vacuum tests and on-orbit observations, suggest that a long-lived contaminant is present in the PC1 which is slowly dissipating. In addition, corrections to the relative zeropoints for the different chips are determined for the F160BW, F170W, and F218W filters.