The W1 and W2 depth-of-coverage is generally a factor of two greater than that for W3 and W4 in the AllWISE Source Catalog. Once detected, sources positions and fluxes were measured by fitting PSF templates simultaneously to the ”stack” ofĪll Single-exposure images in all WISE bands that cover their locations. On the deep, coadded AllWISE Atlas Images. The AllWISE Source Catalog contains accurate positions, motion measurements, photometry and ancillary information for 747 634 026 objects that were detected

Least 90% confidence for magnitudes brighter than Rf = 19.5, and the catalogue is complete to Rf = 20. Outside of the galactic plane, stellar classification is reliable to at Is determined to a 0.13-0.22 mag accuracy as a function of magnitude and photographic pass bands (Rf, Bj, In). Whenĭealing with extended objects, astrometric errors are 20% worse in the case of galaxies and approximately a factor of 2 worse for blended images. Positions are tied to the InternationalĬelestial Reference System for stellar sources, the all-sky average absolute error per coordinate ranges from 0.2 to 0.28 arcsec depending on magnitude. Photometry, and classification for 945 592 683 objects down to the magnitude limit of the plates. The GSC2.3 catalogue contains astrometry, Was distributed soon after its production in 2001, while the GSC2.3 release has been available for general access since 2007. A magnitude-limited (Rf = 18.0) version, GSC2.2, Two catalogues have already been extracted from the GSC-II database and released to the astronomical community. Like its predecessor (GSC-I), the GSC-II was primarilyĬreated to provide guide star information and observation planning support for Hubble Space Telescope. Institute has created from the Palomar and UK Schmidt survey plates and made available to the community. The Guide Star Catalog II (GSC-II) is an all-sky database of objects derived from the uncompressed Digitized Sky Surveys that the Space Telescope Science There are 4 982 212 stars without proper motions. Going forward or backward in time from the central epoch.įor objects without proper motions, the positions are at the central epoch (which actually is UCAC4 observation epoch). Positional errors of stars increase according to the errors in the proper motions when

The proper motions are given at the central epoch. However, a fair number of stars have a vastly different mean epoch, ranging back to about 1947.

In most cases this central epoch will be close to the UCAC observational epoch due to the relatively large RA and Dec) the positional error has its smallest value: the one given in the catalogue for ”sigma position”. At the central epoch (which varies from star to star and is also different for In order to be able to calculate positional errors at any epoch, the central epoch, i.e., the weighted meanĮpoch of the data (UCAC + early epoch other catalogues) is given. Positions in UCAC4 are given at the standard epoch of Julian date 2000.0, thus the UCAC4 is a compiled catalogue. The astrometry provided in UCAC4 is on the Hipparcos system, i.e., the International Celestial Reference System (ICRS), as representedīy the Tycho-2catalogue.

Vicinity in skychart