USNO CCD Astrograph Catalog (UCAC)

 Last update: 2010 Feb 22



UCAC is an astrometric, observational program, which started in February 1998 at CTIO. All sky observations were completed at the Naval Observatory's Flagstaff Station in May 2004, and data reduction was completed in July 2009. The final UCAC3 catalog will be released on August 10, 2009 at the meeting of IAU Commission 8, during the IAU General Assembly in Rio de Janero, Brazil.  DVDs are in production and will be send to customers on the UCAC2 distribution list, and those who already requested it. The catalog is free of charge, although our resources are limited and distribution of the double-sided DVD will take several weeks. The 8 GB binary files will also be made available at CDS soon. For more details, please see the readme_u3 file.

UCAC3 official star numbers

While the MPOS number (last column on each data record) mainly provides a means to identify known high proper motion stars, the primary star identification number should be of the form:


The "3UC" is constant and indicates the UCAC3 catalog. The 3 digit "zzz" number is the zone the star is in, followed by a dash and a 6 digit number which is the record number of the star on that zone. Thus the official designation of the star 42 in zone 7 would be 3UC007-000042.