Stellar photometry with the Hubble Space Telescope Wide-field/Planetary camera - A progress report

摘要

We describe the prospects for the use of the Wide-Field/Planetary Camera (WFPC) for stellar photometry.udThe large halos of the point-spread function (PSF) resulting from spherical aberration and from spatial, temporal, and color variations of the PSF are the main limitations to accurate photometry. Degradations causedudby crowding are exacerbated by the halos of the PSF. Here we attempt to quantify these effects and determine the current accuracy of stellar photometry with the WFPC. In realistic cases, the brighter stars in crowded fields have 0.09 mag errors; fainter stars have larger errors depending on the degree of crowding. We find that measuring Cepheids in Virgo Cluster galaxies is not currently possible without inordinate increases in exposure times.