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   While the Hipparcos/Tycho Catalogs and GSC are used for display
of stars,  when you click for "More Info" on a star, you may get
data from many other catalogs.  Guide will attempt to cross-
reference to the SAO (Smithsonian Astrophysical Observatory), HD
(Henry Draper), Yale,  GCVS (General Catalog of Variable Stars),
WDS (Washington Double Star),  PPM (Position and Proper Motion),
and NSV (New Suspected Variable) catalogs. Each will either provide
additional data,  or a cross-check on the data you've seen in other
catalogs, or both.
                                                                
   There are five galaxy catalogs on the Guide CD-ROM.  The PGC
(Principal Galaxy Catalog 1996) of over 100,000 galaxies forms the
basis for display of small fields.  Data is also shown from the RC3
(Third Revised Catalog),  the Uppsala General Catalog (UGC), the
Morphological Catalog of Galaxies (MCG),  and the European Southern
Observatory extension to the UGC (ESO/Uppsala).

   As with any other problem you may find with Guide,  please let us
know if you find any problems in the data.  At the very least, error
reports can be passed on to those maintaining the data.

24:  ACCESSING GUIDE'S DATA        

   Quite a few programmers have asked about accessing the data on the Guide
CD-ROM from their own programs.  In certain cases, this can be easy to
do;  some of the data (for example,  all of the "user datasets") are in
their original ASCII form,  and are well-documented.  In others,  it can
be a difficult undertaking (e.g.,  the GSC,  Tycho,  and PPM data).  The
compression really is not intended to frustrate people.  But a quick
check will show you that the CD-ROMs are almost completely full;  unless
many larger datasets were highly compressed,  something would have been
omitted.

   Because of the concern about fitting everything on the CDs, a lot of
effort went into compressing the larger datasets. Little was usually
done to smaller datasets,  since compressing them would not have
helped very much anyway.

   Full details on accessing the datasets are available at:

http://www.projectpluto.com/access.htm

   This is updated from time to time;  some datasets are currently
undocumented simply because no one asked about them.  If you have a
particular dataset you'd like to access,  please contact Project Pluto.

25: ACKNOWLEDGMENTS        

   Much of the data for this CD came through the Astronomical Data
Center and/or the Centre des Donnees Astronomiques de Strasbourg:

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