(IAAC) Newer better star catalog available on-line

[Forwarded without explicit permission. -Lew]

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

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,


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.


Bruce Koehn

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