[vsnet-chat 1360] (No Subject in original)

[bas@lowell.Lowell.Edu (Brian Skiff)]

     Since Arne Henden mentioned the revision of the monster USNO star
catalogue, I thought folks would like to know that one can now do searches on
small regions in this catalogue from the Lowell Web site.  Here is a note from
Bruce Koehn about this.
     It is important to note that the catalogue has been re-indexed, so the
(invented) star numbers from USNO-A1.0 are no longer valid within A2.0.
     The catalogue now has 525 million stars, compared to 488 million in A1.0.
     N.B. also, as Arne described, the photometry in the catalogue is somewhat
improved over the original.  Similarly, the astrometric reference is now
the ACT catalogue rather than the GSC, so the positions should be at least
a factor of two better, particularly in the southern sky.

\Brian

++++++++++++++++++++++++++++++++++++++++++

Date: Tue, 6 Oct 1998 12:34:58 -0700 (MST)
From: Bruce Koehn <koehn@lowell.edu>
Subject: USNO-A2.0 catalog available


Dave Monet of the USNO has loaned us copies of the
USNO-A2.0 and USNO-SA2.0 catalogs. With Dave's implicit 
permission, we have copied them to our web site,

http://asteroid.lowell.edu/cgi-bin/koehn/webnet

and the catalogs are available for general use.

>From the documentation,

   "USNO-A2.0 is a catalog of 526,280,881 stars, and is based on a
   re-reduction of the Precision Measuring Machine (PMM) scans that
   were the basis for the USNO-A1.0 catalog.  The major difference
   between A2.0 and A1.0 is that A1.0 used the Guide Star Catalog
   (Lasker et al. 1986) as its reference frame whereas A2.0 uses the
   ICRF as realized by the USNO ACT catalog (Urban et al. 1997)."


One cautionary note: The new catalog has corrections
(additions and deletions). So index numbers used in
the original catalog do not necessarily indicate the
same star in the new catalog. That does not make any
difference on our web page because we don't make 
index numbers available. But it might cause confusion
in other circumstances.

The catalogs are not yet ready for general distribution because no
CD-ROMS have yet been cut. Dave is preparing to have the
CD-ROMs made in the next few weeks. Watch the following web site
for availability.

http://vsnet.usno.navy.mil/pmm/

Regards,
Bruce Koehn

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