The Guide Star Catalogue is an all-sky astrometric and photometric catalog prepared for the operation of the Hubble Space Telescope.
The first set of CD-ROMs contained the Guide Star Catalog - Version 1, with an issue date of 1 June 1989. The second set of CD-ROMs contains the Version 1.1 of the GSC, with an issue date of 1 August 1992. The Guide Star Catalog (GSC) was prepared by the Space Telescope Science Institute (ST ScI), 3700 San Martin Drive, Baltimore, MD 21218, USA. ST ScI is operated by the Association of Universities for Research in Astronomy, Inc. (AURA), under contract with the National Aeronautics and Space Administration (NASA).
The Guide Star Catalog is subdivided into regions, bounded in right ascension and declination, and which are numbered consecutively from 0001 to 9537. Data for each region are stored as separate files; these files are contained in subdirectories, each of which subtends a 7.5 degree zone of declination.
The Guide Star Catalog is distributed as a two CD-ROM set, divided at a declination of -7.5 degrees. A description file and supporting tables are duplicated on both discs. All data files are in FITS (Flexible Image Transport System) table format.
Directory GSC contains subdirectories for the 7.5 degree zones in declination; these subdirectories in turn contain the GSC region files in FITS format for the respective zone. Additional information on the Guide Star Catalog may be found in comments in the FITS headers of the supporting tables.