Home > Agencies & Organisations, Astronomy, Astrophysics, General Astronomy > USNO Releases Final Version of CCD Astrograph Star Catalog

USNO Releases Final Version of CCD Astrograph Star Catalog


The United States Naval Observatory (USNO) has released the Fourth Edition of its USNO CCD Astrograph Catalog (UCAC4), the most precise and comprehensive star catalog ever produced by ground-based instrumentation.  The catalog contains data on about 113 million stars and is complete for all stars from the brightest, Sirius, to about 16th magnitude.  Stars brighter than about 8th magnitude are supplemented from other sources, mainly the FK6, Hipparcos and Tycho Catalogs, and were not directly observed by the astrograph.

In addition to the sheer number of stars that the UCAC4 entails, it is the
precision and accuracy of the stars’ positions that set this catalog apart from all of its predecessors.

Astronomers measure the sky in terms of angular degrees, minutes, and seconds of arc.  The apparent size of the disc of the Full Moon is approximately 30 arcminutes, or one-half of a degree.  The apparent size of the disc of Mars at its most favorable oppositions is just over 25 arcseconds, slightly less than one-half of an arcminute.  One arcsecond is the apparent size that a U.S. penny coin would appear if it were viewed from a distance of about 2.4 miles (3.9 kilometers).

Full Story: http://www.usno.navy.mil/USNO/tours-events/usno-releases-final-version-of-ccd-astrograph-star-catalog-ucac4-8-23-12

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