Cosmic shear from STIS pure parallels - I. Data

Following the second HST servicing mission in 1997 when the STIS instrument was installed and the capability for parallel observations was enhanced, a substantial archive of non-proprietary parallel data has been accumulating . In this paper, we discuss the use of unfiltered STIS imaging data for a p roject that requires deep observations along as many independent lines-of-s ight as possible. We have developed a technique to determine which datasets in the archive can safely be co-added together and have developed an itera tive co-addition technique which enabled us to produce 498 high-quality, de ep images. The principal motivation for this work is to measure the Cosmic Shear on small angular scales and a value derived from these data will be p resented in a subsequent paper. A valuable by-product of this work is a set of high quality combined fields which can be used for other projects. The data are publicly available at http://www.stecf.org/projects/shear/.