Gravitational lensing of quasars as seen by the Hubble Space Telescope Snapshot Survey

Results from the ongoing HST Snapshot Survey are presented, with emphasis on 152 high-luminosity, z greater than 1 quasars. One quasar among those observed, 1208 + 1011, is a candidate lens system with subarcsecond image separation. Six other quasars have point sources within 6 arcsec. Ground-based observations of five of these cases show that the companion point sources are foreground Galactic stars. The predicted lensing frequency of the sample is calculated for a variety of cosmological models. The effect of uncertainties in some of the observational parameters upon the predictions is discussed. No correlation of the drift rate with time, right ascension, declination, or point error is found.