The Guide Star Catalog (GSC), also known as the ''Hubble Space Telescope, Guide Catalog'' (''HSTGC''), is a
star catalog compiled to support the
Hubble Space Telescope 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
A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...
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.
History
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,
SAOC or
CPC 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 Tycho is a masculine given name, a latinization of Greek Τύχων, from the name of Tyche ( grc-gre, Τύχη, link=no), the Greek goddess of fortune or luck.
The Russian form of the name is ''Tikhon'' (Тихон).
People
Given name
* Tycho ...
was created by the Hipparcos/Tycho international consortia in preparation for the
Hipparcos
''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...
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. This version reduces the plate-based position-dependent and magnitude-dependent systematic errors. The
PPM and
AC 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 and the astrometry team of the Astronomical Observatory of Torino (Italy). 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 (2.3.4) is in active use for accurately positioning the
Hubble Space Telescope.
See also
*
Hubble Guide Star Catalog - Astrographic Catalog/Tycho
The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...
(GSC-ACT)
*
Hubble Space Telescope
*
Space Telescope Science Institute
*
Star catalog
*
Fine Guidance Sensor (HST)
Fine Guidance Sensor (FGS) for the Hubble Space Telescope is a system of three instruments used for pointing the telescope in space, and also for astrometry and its related sciences. Each FGS uses a combination of optics and electronics to prov ...
References
External links
GSC I and GSC II home
{{Hubble Space Telescope
Hubble Space Telescope
Astronomical catalogues of stars