		 xsky - an interactive sky atlas for X



xsky is an X Window  System  program which is essentially an interactive sky
atlas.   The familiar actions of scrollbars,  sliders, and pointer  gestures
such  as  clicking  and  rubberbanding can be used  to move around the  sky,
adjust the magnification, select a  region to  view,  and  bring up detailed
catalog  information  on  any object.   Objects can  be  located  by name or
position, and labelled with either catalog labels or custom user labels.

Stars  are plotted with  colors corresponding  to spectral  class,  and size
corresponding to  apparent magnitude.   Non-stellar  objects  are  drawn  in
several shapes according to the type of object represented.  Right ascension
and  declination lines can  be generated, and  constellation boundaries  are
available.   A  PostScript file  containing  all  this  information  can  be
generated  for printing.  For a complete exposition of xsky's  capabilities,
please see the SUMMARY file in the distribution.

xsky  makes  use  of  machine-readable  astronomical  object  catalogs  made
available by the National Space Sciences Data Center, located at the Goddard
Spaceflight Center  in Greenbelt, Maryland, which  is  administrated by  the
National  Aeronautics and  Space Administration.  Thanks are due to them for
providing this much-needed data distribution service.

Supported catalogs are (abbreviations used by xsky in parentheses):
    a)  the Yale Catalog of Bright Stars (YBS)
    b)  the Revised New General Catalog of Non-Stellar Objects (RNGC)
    c)  the Revised Optical Catalog of Quasi-Stellar Objects (QSO)

Support is included  for the following catalogs, but the catalogs themselves
are not included in this distribution:
    d)  the Smithsonian Astrophysical Observatory Star Catalog (SAO)
    e)  the General Catalog of Variable Stars (VAR)
    f)  the Washington Catalog of Double Stars (DBL)

Support is included for the following catalogs on the NASA Astronomical Data
Center CD-ROM:
    g)  the Bright Star Catalog, 5th revised edition (BSC5)
    h)  the Smithsonian Astrophysical Observatory Star Catalog, J2000
								(SAOJ2000)
    i)  the Washington Catalog of Double Stars (WDS)
    j)  the General Catalog of Variable Stars (GCVS)
    k)  the New General Catalog of Nebulae and Clusters - 2000.0 (NGC2000)
    l)  the Uppsala General Catalog of Galaxies (UGC)

Please  note  that catalogs (a)  -  (f)  are supported  only in the abridged
versions available as part of the xsky distribution.  Catalogs (a) - (c) are
distributed with xsky, and catalogs (d)  - (f) are available  separately via
anonymous FTP.

Additionally, xsky supports a user catalog;  there is an example in the file
usercat.example,  and  the comments  in  user.c  document  the  format  more
precisely.   The intention of the user  catalog is to enable the addition of
comets  or  asteriods  to  create customized  finder  charts  for  transient
objects.

This  program has been  rather thoroughly tested  under Ultrix, running both
the DEC X11R4 server and the MIT X11R5 server.  It builds from the Imakefile
properly  under  Ultrix  and SunOS.  A  Makefile.std  is included  for those
unable or unwilling to fool with imake; it should  be necessary only to edit
the INCLUDES line to use it under SunOS.  xsky has gotten a lot less testing
under SunOS, but all the functionality has been checked out in a preliminary
fashion.  Both the cc and gcc compilers have been used to compile a runnable
version of xsky under SunOS and Ultrix.

xsky  also works out-of-the-box  on a  wide variety  of other Unix  systems;
thanks  to  its  total  reliance on Athena widgets,  essentially  no porting
effort is required in the usual case.

Suggestions for improvements  will also be  noted,  but please be aware that
this is a part-time, off-hours project for me, and implementation could take
awhile.  It would certainly go faster  if you  included  the code along with
your  suggestions!    Any  such  contributions,  if  incorporated,  will  be
gratefully acknowledged.
