Carte du Ciel
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Carte du Ciel(kart dew syel) A whole-sky photographic atlas proposed in Paris in 1887 and planned to include stars of magnitude 14 or brighter. This ambitious scheme involved 18 observatories in photographing areas of the sky only 2° square using specially designed 33-cm refracting telescopes. The survey has never been fully completed. Technical advances have since made it possible to photograph much greater areas with very much less work. The associated Astrographic Catalog, listing the positions of stars down to 12th magnitude, was essentially complete by 1958. The United States Naval Observatory (USNO) in co-operation with other institutions completed the process of converting the printed Astrographic Catalog into computerized format by the mid-1990s, updating the star positions to epoch 2000.0 in accordance with the Hipparcos Catalog. The resulting document, AC 2000 , was released on CD-ROM in 1997. In 2001, following its collaboration with the University of Copenhagen Observatory in Denmark, on the Tycho-2 catalog, which uses AC 2000 data for many of its proper motions, the USNO issued a revised version of AC 2000, called AC 2000.2 . This revision is also available on CD-ROM. AC 2000.2 is a whole-sky catalog listing more than 4.6 million stars.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006