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The reductions of the USNO Short-$J$ plates taken in conjunction with the Palomar Observatory Sky Survey II are in progress, and we anticipate that the first version of this catalog, UJ1.0, will be in the final stages of compilation. The $UJ$ plates are 3 minute $J$ plates taken at the POSS-II field centers within 30 days of the accepted Survey $J$ plates. (The notation $UJ$ arises from the plate labels: the $U$ stands for USNO and not an ultraviolet bandpass.) Their purpose is to provide an astrometric bridge between POSS-II and optical astrometric catalogs such as ACRS, PPM, HIPPARCOS, and TYCHO. This paper will discuss the astrometric stability of the plate measuring machine (the PMM), and the strategy and success of mapping the $UJ$ plates into the optical reference frame(s).
