Guide Star Catalog - AbsoluteAstronomy.com

The Guide Star Catalog is also known as the Hubble Space Telescope, Guide Catalog (HSTGC). It is a star catalog compiled to support the Hubble Space Telescope

Hubble Space Telescope

The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...

with targeting off-axis stars. GSC-I contained approximately 20,000,000 stars with apparent magnitudes of 6 to 15. GSC-II contains 945,592,683 stars out to magnitude 21. As far as possible, binary star

Binary star

A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

s and non-stellar objects have been excluded or flagged as not meeting the requirements of Fine Guidance Sensors. This is the first full sky star catalog created specifically for navigation in outer space.

Version 1.0

The first version of this catalog was published in 1989. The first catalog was created by digitizing photographic plates produced by the Palomar Schmidt Quick-V survey for the northern hemisphere and the UK Schmidt SERC-J survey for the southern hemisphere. This catalog contains objects in the magnitude range 7-16 and the classification was biased to prevent the use of a non-stellar object as a guide star. The photometry is based on a photoelectric sequence (9-15th mag) near the center of each Schmidt plate. Stellar photometry was performed in a manner that would systematically reject galaxies. Astrometry was determined using the AGK3

Astronomische Gesellschaft Katalog

The Astronomische Gesellschaft Katalog is an astrometric star catalogue. Compilation for the first version, AGK1, was started in 1861 by Friedrich Argelander and published between 1890 and 1954, listing 200 000 stars down to ninth magnitude....

, SAOC

Smithsonian Astrophysical Observatory Star Catalog

The Smithsonian Astrophysical Observatory Star Catalog is an astrometric star catalogue. It was published by the Smithsonian Astrophysical Observatory in 1966 and contains 258,997 stars. The catalogue was...

or CPC

Cape Photographic Catalogue

The Cape Photographic Catalogue is a star catalog containing 68,467 stars in the Southern Hemisphere whose declinations are either between −30° and −40° or between −52° and −90°. It contains positions, proper motions, magnitudes, and spectral types, and was published by the Cape Observatory...

catalog stars depending on plate declination. Although the relative astrometry (required for HST) is about 0.3 arc seconds, there are known systematic errors near the plate edges of 1 to 2 arc seconds.

Version 1.1

The first revision of the catalog was published in 1992. The Tycho Input Catalog was created by the Hipparcos/Tycho international consortia in preparation for the Hipparcos

Hipparcos

Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...

satellite mission. They produced a catalog containing the best available data for all stars to magnitude 11. Adding the bright star data from this catalog to the GSC produced a complete all-sky catalog down to the GSC limiting magnitude. In addition, many of the false objects due to artifacts around the halos and diffraction spikes of the bright stars were identified and corrected as well as a number of reported errors. A number of astrographic plates centered on southern hemisphere bright stars (of magnitude less than 3) were also processed and added to the catalog. This was the version used by HST operations prior to cycle 15.

Version 1.2

Version 1.2 was published in 2001. It was produced in collaboration with the Astronomisches Rechen-Institut in Heidelberg

Heidelberg

-Early history:Between 600,000 and 200,000 years ago, "Heidelberg Man" died at nearby Mauer. His jaw bone was discovered in 1907; with scientific dating, his remains were determined to be the earliest evidence of human life in Europe. In the 5th century BC, a Celtic fortress of refuge and place of...

. This version reduces the plate-based position-dependent and magnitude-dependent systematic errors. The PPM

PPM Star Catalogue

The PPM Star Catalogue is the successor of the SAO Catalogue. It contains precise positions and proper motions of 378,910 stars on the whole sky in the J2000/FK5 coordinate system....

and AC

Carte du Ciel

The Carte du Ciel and the Astrographic Catalogue were two distinct but connected components of a massive international astronomical project, initiated in the late 19th century, to catalogue and map the positions of millions of stars as faint as 11th or 12th magnitude...

reference catalogs were used and absolute position errors have been reduced to between 0.3 and 0.4 arc seconds.

Catalog format

When quoting a catalog entry, the format is GSC FFFFF-NNNNN, or alternately, GSCfffff0nnnnn (fffff0nnnnn). The F-sequence references a Hubble sky region code.

Guide Star Catalog II

A significant expansion of the catalog, Guide Star Catalog II, was published in 2008. The Guide Star Catalog II (GSC-II) was compiled by the Catalog and Surveys branch of the Space Telescope Science Institute

Space Telescope Science Institute

The Space Telescope Science Institute is the science operations center for the Hubble Space Telescope and for the James Webb Space Telescope...

. It has entries for 945,592,683 stars, and has positions, classifications, and magnitudes for 455,851,237 stars. The latest revision of this version (2.3.2) is in active use for accurately positioning the Hubble Space Telescope