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Beginning of ReadMe : I/294A The UCAC2 Bright Star Supplement (Urban+, 2006) ================================================================================ The UCAC2 Bright Star Supplement. Urban S.E., Zacharias N., Wycoff G.L. U.S. Naval Observatory, Washington D.C. 2004-2006 <Astron. J. (unpublished) (2004)> ================================================================================ ADC_Keywords: Positional data ; Proper motions ; Stellar distribution ; Surveys Keywords: astrometry - stars - fundamental parameters - catalogs - proper motions - cross identifications Abstract: The UCAC2 Bright Star Supplement (UCAC2 BSS) is meant to be used with the Second U.S. Naval Observatory CCD Astrograph Catalog (UCAC2, CDS Catalogue number I/289) to fill in the missing bright stars and yet-to-be observed northern regions of the UCAC2. In total 430,000 stars, mostly from the region north of +40 degrees declination, make up this supplementary data set. All astrometric data were extracted from either the Hipparcos Catalogue or the Tycho-2 Catalogue; photometric data were extracted from the Hipparcos, Tycho-2, and 2MASS catalogues. Cross references between the data sources are given. Description: The Second U.S. Naval Observatory CCD Astrograph Catalog (UCAC2) has now been completed and distributed (see CDS catalogue I/289). The UCAC2 catalogue contains stars in the R 8-16 magnitude range with sky coverage from the South Celestial Pole to a ragged northern boundary between declination +40 to +55 degrees. Details of that catalogue and project can be found elsewhere (see UCAC web page at http://ad.usno.navy.mil/ucac/ ). Two noticeable features of the UCAC2 are its lack of bright stars and its incomplete sky coverage. The former is a result of the finite dynamic range of the data acquisition system and observing procedures; they are optimized for the magnitude range of r 8-16. The brightest stars are over-exposed and little astrometric information is gained. The latter is a result of the on-going nature of the project. The UCAC2 covers over 85% of the sky; the remaining Northern Celestial Pole area is currently being observed and reduced. It is expected that the final UCAC catalogue will be released in 2006. These two features -- the lack of bright stars and the lack of full sky coverage -- are the reasoning behind the UCAC2 Bright Star Supplement (UCAC2 BSS). The UCAC2 BSS is somewhat of a misnomer on two counts. First, there are no UCAC2 data in it. Instead, all astrometric data were extracted from the Hipparcos main catalog (HIP), the Hipparcos Double and Multiple System Annex (DMSA), the Tycho-2 main catalog, or the Tycho-2 Supplement 1. Photometric data were taken from the above catalogues and the Two-Micron All Sky Survey (2MASS). Second, the UCAC2 BSS contains not only bright stars, but all stars from the above mentioned catalogs not found in the UCAC2. This not only includes the spatial area covered by the UCAC2, but also the far northern regions. For this reason, most stars in the UCAC2 BSS are north of +40 degrees. Additional information, including a very extensive catalogue introduction can be found on the UCAC project website at http://ad.usno.navy.mil/ucac/ . This website also contains a binary version of the UCAC2 BSS catalog. This version is very similar in format to the UCAC2 binary data, therefore much of the same software can be utilized. The software can be downloaded from the project webpage. UCAC2 Bright Star Supplement Data Format: ---------------------------------------- The data are arranged in 5 degree zones of declination, starting from the South Celestial Pole, and are sorted by Right Ascension within each zone. The running ID numbers go from 50,000,001 to 50,430,000; they are unique, and have no gaps. The start of the ID number at 50,000,001 was chosen so it did not conflict with any UCAC2 ID number.