Hubble Guide Star Catalog – Astrographic Catalog/Tycho

The Hubble Guide Star Catalog – Astrographic Catalog/Tycho (GSC-ACT) is an astronomical catalog. It contains the twenty million stars of the Hubble GSC, version 1.1, recalibrated using the U.S. Naval Observatory's ACT (Astrographic Catalog/Tycho). By 2009 it was considered obsolete, superseded by such catalogues as GSC-2.2, B1.0, A2.0, and especially UCAC-3.^[1]

GSC-ACT was a re-calibration of the Guide Star Catalog version 1.1 for Hubble.^[2] The original GSC dated to 1989,^[3] and one of the reasons for an update was improvements to star catalogs that took place after that time.^[4] In this case the ACT catalog was used, which had for example more stars and whereas the GSC 1.1 had 3rd order fit for plate distortions, the ACT has a five-order available.^[5] Another improvement of the GSC 1.1 was the GSC 1.2.^[6]

GSC-ACT uses five classification codes:^[7]

• 1 Star
• 2 Galaxy
• 3 Non-Star
• 4 Artefact

See also

• Guide Star Catalog
• Tycho catalog
• Tycho-2 Catalogue

References

1. Gray, Bill. "GSC-ACT files and information". www.projectpluto.com. Retrieved 2017-03-03.
2. "VizieR". vizier.u-strasbg.fr. Retrieved 2017-03-03.
3. Gray, Bill. "GSC-ACT files and information". www.projectpluto.com. Retrieved 2017-03-03.
4. Gray, Bill. "GSC-ACT files and information". tdc-www.harvard.edu. Retrieved 2017-03-03.
5. Gray, Bill. "GSC-ACT files and information". tdc-www.harvard.edu. Retrieved 2017-03-03.
6. Gray, Bill. "GSC-ACT files and information". tdc-www.harvard.edu. Retrieved 2017-03-03.
7. "GSC-ACT Catalog". ledas-www.star.le.ac.uk. Retrieved 2017-03-03.

External links

• Overview of the GSC-ACT