// Workers AI · dad joke modeWhy was the Hubble catalog star-struck? It had a stellar reputation.
The Hubble Guide Star Catalog – Astrographic Catalog/Tycho (GSC-ACT) is an astronomical catalog which records 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 By 2009 it was considered obsolete, superseded by such catalogues as GSC-2.2, B1.0, A2.0, and especially UCAC-3.[1]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,[1] and one of the reasons for an update was improvements to star catalogs that took place after that time.[3] In this case the ACT catalog was used, which had for example more stars; whereas the GSC 1.1 had a third-order fit for plate distortions, the ACT has a five-order available.[3] Another improvement of the GSC 1.1 was the GSC 1.2.[3]
GSC-ACT uses five classification codes:[4]
- 1 Star
- 2 Galaxy
- 3 Non-Star
- 4 Artefact
See also
[edit]References
[edit]- 1 2 Gray, Bill (9 April 2003). "GSC-ACT files and information". www.projectpluto.com.
- ↑ "VizieR". vizier.u-strasbg.fr. Retrieved 2017-03-03.
- 1 2 3 Gray, Bill (16 December 1999). "GSC-ACT files and information". tdc-www.harvard.edu.
- ↑ "GSC-ACT Catalog". ledas-www.star.le.ac.uk. Retrieved 2017-03-03.
External links
[edit]
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