Sloan Digital Sky Survey III
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USNOPHOTO SDSS objects that match to USNO-B objects have their match parameters stored here
The source for this is the USNO-B1.0 catalog (Monet et al. 2003, AJ, 125, 984). This is simply the closest matching USNO-B1.0 object. See the ProperMotions table for proper motions after recalibrating USNO and SDSS astrometry. USNO-B contains five imaging surveys, two early epochs from POSS-I, and three later epochs from POSS-II, SERC and AAO.