The Guide Star Catalog 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. The GSC I catalog is used for the control and target
acquisition of the Hubble Space Telescope.
The Guide Star Catalog II
is an all-sky optical 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. The GSC II is an all-sky catalog of approximately 2
billion stars and galaxies containing positions, magnitudes,colors and proper
motions complete to a minimum of V =18.
The Guide Star Photometric Catalog
is an all-sky set of photoelectrically determined BV sequences in the
magnitude range from 9 to 15, generally near the centers of the fields of the
is an all-sky catalog of secondary "standard-stars" that were used to perform the photometric calibration of the GSC-II. GSPC
II is generally an extension of GSPC I sequences to V=19 in (B), V and R
passbands based on CCD photometry. Its purpose is calibration of
the GSC-II. New northern sequences are being added to support the POSS-II.