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 . By 2009 it was considered obsolete, superseded by such catalogues as , , , and especially UCAC-3. GSC-ACT uses five classification codes: * 1 Star * 2 Galaxy * 3 Non-Star * 5 Artifact