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Description
The UCAC1 is a high density, highly accurate, astrometric catalog of over 27 million stars in the Southern Hemisphere in the magnitude range of about 8 to 16. This version is the first release of an ongoing project to observe the entire sky; for up-to-date information see the Web page at http://ad.usno.navy.mil/ad/ucac/ . The UCAC1 is a preliminary catalog. By avoiding all "problem cases" (see details in the "intro.txt" file) it is not complete. Positions, proper motions and errors are provided, together with approximate magnitudes in the 579-642nm range. The positional precision is about 20 mas for 9 to 14 mag and 70 mas at 16th mag. The errors of the proper motions are very heterogeneous, ranging from 1 to 35 mas/yr. The UCAC is an observational program using the U.S. Naval Observatory Twin Astrograph and a 4kx4k CCD camera, covering just over 1 square degree per frame with a scale of 0.9"/pixel. Observations started in January 1998 at Cerro Tololo Interamerican Observatory (CTIO) and are continuing. This first catalog contains data observed through 07 November 1999 at which time about 80% of the Southern Hemisphere was completed. Full sky coverage is expected by early 2003 after a re-location of the instrument to the Northern Hemisphere planned for early 2001. The UCAC1 is also available on CD-ROM from the US Naval Observatory. Direct request to nz@pisces.usno.navy.mil with UCAC1 in the subject string.
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