THE FOURTH US NAVAL OBSERVATORY CCD ASTROGRAPH CATALOG (UCAC4)

• Published in: The Astronomical journal Vol. 145; no. 2; pp. 1 - 14
• Main Authors: Zacharias, N, Finch, C T, Girard, T M, Henden, A, Bartlett, J L, Monet, D G, Zacharias, M I
• Format: Journal Article
• Language: English
• Published: United States 01.02.2013
• Subjects: ACCURACY; APERTURES; Astronomical bodies; Astronomical catalogs; ASTRONOMY; ASTROPHYSICS; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHARGE-COUPLED DEVICES; COORDINATES; ERRORS; Lenses; Naval; NEAR INFRARED RADIATION; PHOTOMETRY; Position measurement; PROPER MOTION; SOUTHERN HEMISPHERE; STARS
• ISSN: 0004-6256; 1538-3881; 1538-3881
• DOI: 10.1088/0004-6256/145/2/44

UCAC4 is an updated version of UCAC3 with about the same number of stars also covering all-sky. Bugs were fixed, Schmidt plate survey data were avoided, and precise five-band photometry was added for about half the stars. Astrograph observations have been supplemented for bright stars by FK6, Hipparcos, and Tycho-2 data to compile a UCAC4 star catalog complete from the brightest stars to about magnitude R = 16. Epoch 1998-2004 positions are obtained from observations with the 20 cm aperture USNO Astrograph's "red lens," equipped with a 4k by 4k CCD. Mean positions and PMs are derived by combining these observations with over 140 ground- and space-based catalogs, including Hipparcos/Tycho and the AC2000.2, as well as unpublished measures of over 5000 plates from other astrographs. These data are supplemented by 2MASS near-IR photometry for about 110 million stars and five-band (B, V, g. r, i) APASS data for over 51 million stars.