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Description
The UCAC2 is the second release of the ongoing UCAC project, designed
to observe the entire sky for R magnitudes of about 7.5 to 16. The
observed positional errors are about 20 mas for the stars in the 10
to 14 magnitude range, and about 70 mas at the limiting magnitude
of R ~16. For up-to-date information on the project, see our web page
at http://ad.usno.navy.mil/ucac/ . This web page will also serve as
the location that the UCAC team will post addenda to the UCAC2 catalog.
The UCAC2 is a high density, highly accurate, astrometric catalog of
48,330,571 stars covering the sky from -90 to +40 degrees in declination
and going up to +52 degrees in some areas. The northern limit is a
function of right ascension. Proper motions and photometry are
provided for all stars. Positions and proper motions are on the
ICRS (International Celestial Reference System) and given at the epoch
J2000.0.
The UCAC2 has a number of major differences with respect to UCAC1.
These differences include:
- much larger sky coverage
- reduced systematic errors of CCD observations
- positions given at a standard epoch (J2000.0)
- the addition of several new catalogs for improved proper motions
- photometry in the J, H, and K_s bands from the 2MASS project
- data in binary format for direct access
- inclusion of software to aid users in quick access of the data
Additional details of the data are found in Sections 3, 4, and 5 of
this document.
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