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N. Zacharias (USNO), M.I. Zacharias (USRA / USNO)
The U.S. Naval Observatory (USNO) CCD Astrograph Catalog (UCAC) project begun observing from the Northern Hemisphere in November 2001, continuing the project started at CTIO in 1998. A catalog (UCAC2) of positions and proper motions for about 40 million stars (8 to 16 mag) is being constructed, covering the sky from the South Celestial Pole to about +30 degree declination.
For the first time, the large number of available calibration observations are being utilized to significantly improve the systematic error corrections, beyond what has been achieved with the UCAC1 release. Due to the poor charge transfer efficiency of the 4k by 4k chip, systematic errors exist in the raw data mainly as a function of magnitude and x-coordinate, in various combinations. Important in the determination of these systematic errors is 1) the ability of the astrograph to operate on both sides of the pier, allowing frames to be taken which are flipped by 180\circ in orientation with respect to the sky; and 2) the stability of the instrument, giving repeatable results over years of operation.
Other types of systematic errors and the expected positional accuracy of the upcoming UCAC2 will also be discussed.
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The author(s) of this abstract have provided an email address for comments about the abstract: nz@usno.navy.mil
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Bulletin of the American Astronomical Society, 34, #3
© 2002. The American Astronomical Society.