US Naval Observatory | 2015 Apr 24
The United States Naval Observatory (USNO) has released the First Edition of its USNO Robotic Astrometric Telescope (URAT) star catalog, URAT1. This catalog is the follow-on to the Observatory’s previous USNO CCD Astrograph Catalog (UCAC4). The new catalog contains positional data on about 228 million stars with a magnitude range of 3.0 to 18.5 for a bandpass of 680 to 750 nanometers between declinations of +89.5 degrees and -15 degrees. Longer integration times and more sensitive, backside CCDs allowed for a substantial increase in limiting magnitude, resulting in a nearly 4-fold increase in the average number of stars per square degree as compared to UCAC.[attachment=0]urat1-skyden.jpg[/attachment]
URAT1 is supplemented by preliminary proper motions derived exclusively from 2-epoch URAT1 and Two Micron All Sky Survey (2MASS) data (at around epoch 2000) resulting in proper motion errors of typically 5 to 8 milliarcseconds (mas)/year. Photometry from 2MASS and the American Association of Variable Star Observers Photometric All-Sky Survey (APASS) is added for stars in common with URAT1. ...
URAT1 will be available to users through the astrometric catalog server at the Strasbourg Astronomical Data Center (CDS) as Catalog I/329.
Current plans call for a second URAT2 data release in about a year, which will include 3+ years of operations, proper motions and parallaxes (of nearby stars) derived from URAT data.