Как-то пишут по-советски... Какова точность нового каталога? Какая предельная зв. величина? В каких фильтрах? Покрытие?
Да вроде там написано все... А попасть в тестеры, скорее всего они разошлют бета-версии тем кто тестил UCAC2,3...
Overview
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UCAC4 is a compiled, all-sky star catalog covering mainly the 8 to
16 magnitude range in a single bandpass between V and R. Positional
errors are about 15 to 20 mas for stars in the 10 to 14 mag range.
Proper motions have been derived for most of the about 113 million
stars utilizing about 150 other star catalogs with significant epoch
difference to the UCAC CCD observations. These data are supplemented
by 2MASS photometric data for about 110 million stars and 5-band
(B,V,g,r,i) photometry from the APASS (AAVSO Photometric All-Sky
Survey) for about 50 million stars. UCAC4 also contains error estimates
and various flags. All bright stars not observed with the astrograph
have been added to UCAC4 from a set of Hipparcos and Tycho-2 stars.
Thus UCAC4 should be complete from the brightest stars to about R=16,
with the source of data indicated in flags. UCAC4 also provides a
link to the original Hipparcos star number with additional data such
as parallax found on a separate data file included in this release.
The proper motions of bright stars are based on over 140 catalogs,
including Hipparcos and Tycho, as well as all catalogs used for the
Tycho-2 proper motion construction. Proper motions of faint stars are
based on re-reductions of early epoch SPM data (-90 to about -20 deg
Dec) and NPM (PMM scans of early epoch blue plates) for the remainder
of the sky. The early epoch SPM data have also been combined with
late epoch SPM data to arrive at proper motions partly independent
from UCAC4 (Girard et al. 2011). The NPM data used in UCAC4 are not
published. No Schmidt plate data are used in UCAC4.
Differences between various versions of UCAC
--------------------------------------------
UCAC1 = initial results covering small sky area in the south (obsolete)
UCAC2 = -90 to about +50 deg Dec, 48 mill.stars, restricted to good
astrometry sources (mostly obsolete by now)
UCAC3 = first all-sky catalog, push for faint limit, not as clean
as UCAC2 data, several bugs affecting ~ 1 % of stars (obsolete)
UCAC4 = improved version of UCAC3 = final release
UCAC3 features a number of major differences with respect to UCAC2:
- complete sky coverage
- re-reduction of the pixel data with better modeling
- double stars are resolved to the limit of the data
- significantly improved photometry from CCD data
- slightly deeper limiting magnitude with larger number of stars/area
- reduced systematic errors of CCD observations
- the addition of several new catalogs for improved proper motions
- photometry in the B, R, and I bands from the SuperCosmos project
- minor planet observations have been sorted out
- identification of more high proper motion stars
- match with 2MASS extended sources and LEDA galaxies
UCAC4 is largely based on UCAC3 (same pixel data reductions),
however, has a number of critical improvements over UCAC3:
- bug fixes (e.g. missing stars, multiple entries, mag.eq. corrections)
- use NPM data to derive proper motions of faint stars north of -20 Dec
- final tweak of systematic error corrections brings it closer to UCAC2
- photometry in the B, V, g, r and i bands from APASS for 30 mill.stars
- use APASS photometry to calibrate ("flatten") instrumental mags
- removal of photometric bias as function of CCD x-coordinate
- add brightest stars from FK6, Hipparcos and Tycho-2 catalogs
- link to Hipparcos star numbers and inclusion of Hipparcos 2007 release
data like parallaxes
