  The measurement of cosmic shear requires deep imaging with high image quality
on many lines of sight to sample the statistics of large-scale structure. The
expected distortion of galaxy images by cosmic shear on the STIS angular scale
is a few percent, therefore the PSF anisotropy has to be understood and
controlled to an accuracy better than 1%. In this poster we present the
analysis of the PSF of STIS and a preliminary cosmic shear measurement using
archival data from the STIS pure parallel program to show that the STIS camera
on-board HST is well suited for our project. The data reduction and catalog
production are described in an accompanying paper (astro-ph/0102330).
