Guide Star Catalog

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Last Updated Jan 2001

Copyright 2001 The Association of Universities for Research in Astronomy, Inc. All Rights Reserved.

998,402,801 unique GSCII Objects
and counting!

The above image illustrates the deeper magnitude limit of the GSC2 compared to the GSC 1.

The Catalogs and Surveys Branch of the Space Telescope Science Institute has been digitizing the photographic Sky survey plates from the Palomar and UK Schmidt telescopes to produce the GSC and DSS. These catalogs support ground and space-based telescope operations and provide a valuable scientific resource to the astronomical community.

The Guide Star Catalog II (GSC II) is an all-sky catalog based on 1" resolution scans of the photographic Sky Survey plates, at two epochs and three bandpasses, from the Palomar and UK Schmidt telescopes (DSS). The all-sky, magnitude-limited Telescope Operations version, GSC2.2, contains positions, classifications, and magnitudes for 435,457,355 objects, and is now available to the community via the WWW.

The Guide Star Catalog I (GSC I) is an all-sky optical catalog of positions and magnitudes of approximately 19 million stars and other objects in the 6th to 15th magnitude range. GSC I catalog is used for the control and target acquisition of the Hubble Space Telesope.

Please read the fine print:

data copyrights data use policy data acknowledgements

We wish to thank the following institutions for supporting STScI with the construction of the GSC-II

European Space Agency - Astrophysics division
International GEMINI project
Osservatorio Astronomico di Torino
Space Telescope -European Coordinating Facility