Note: Errors found in the Hipparcos catalogue are reported in the file errata.htx
Note that the errors on the
proper motions are large (∼50mas/yr), and therefore the positions
computed at an epoch different from 1991.25 have a large (∼0.4")
The Tycho Epoch Photometry data can
be accessed from the morePhoto column
(includes VT, BT and Hp photometric data for Hipparcos stars
contains 526,280,881 sources, and is based on a
re-reduction of the Precision Measuring Machine (PMM) scans
from POSS-I O and E plates (>=-18°) and SRC-J and
ESO-R plates (<=-20°).
USNO-A2.0 was created by Dave Monet (Flagstaff Station, U.S. Naval Observatory.
The major difference between USNO-A2.0 and its previous version
USNO-A1.0 is that A1.0 used the
Guide Star Catalog as its reference frame whereas
A2.0 uses the ICRF as realized by the
USNO ACT catalog (Urban et al. 1997).
The VizieR search engine uses an
on-line compressed version
(3.6Gbytes) which was generated at CDS.
Note: The Guide Star Catalog has been constructed to support the
operational need of the Hubble Space Telescope.
It contains over 25 million positions for about 19 million
objects, of which more than 15 million are classified as stars.
The version 1.2 is a new astrometric reduction which results in
absolute position errors about 0.3-0.4 arcsec.
(see GSC pages at URL http://www-gsss.stsci.edu/gsc/gsc.html)
Note: the J2000 coordinates are not part of the original catalogue; their accuracy can be low, see the CooFlag column
Note: Detailed introduction can be found in intro.tex (see also http://aries.usno.navy.mil/ad/ac.html) Direct links to Hipparcos and Tycho observations are provided from the relevant columns.
Note: Many errors detected in the positions given in the catalogue, especially in the sign of the declination in the zones -1°<δ<+1°
Note: See also the ARICNS (Astronomische Rechen-Institut database for Nearby Stars); some errors can be found in notes.tex
Note: The ``short'' version of the catalogue can be retrieved by a selecting *+* in the SEQflags column
Note: The column expnum provides an access to details on the exposures, and a link to the Preview and Retrieval System via the CADC
Note: Details of surveyed literature