This is a collection of files in xephem database format. Included here are
asteroids, comets, stars, deep-sky objects, earth satellites and spacecraft.
Work on the databases is a major project in itself. There are bound to be
errors. Authoritative contributions welcome.

The sample XEphem.ad resource settings assume the database files are in this
directory. For reference, the relevant resource is: XEphem.DBdirectory: edb



YBS.edb are all of the entries in the Yale Bright Star Catalog which have
a Bayer and/or a Flamsteed number. A few with common names have been renamed.
Contact the author if you would like the remaining stars (ecdowney@noao.edu).

Messier.edb is the Messier catalog.

Asteroids are in asteroids.edb. They are named with their sequence number
followed by their common name, if one has been assigned. The list goes to
6160.

Deep-sky entries from the Saguaro Astronomy Club database Version 6.0 are
in SAC.edb. The NGC objects have been pulled out and put into NGC.edb. The
Messier objects have been commented out and moved into the messier.edb. Some
objects in the SAC database do not have well-accepted magnitudes.  These
entries are included but have special magnitude values of 99.9 or 79.9;
99.9 means no magnitude was available and 79.9 applies to dark nebulae.
NGC 666, 916 and 4192A/B are from NSSDC Catalog 7001B.

Orbital elements for several spacecraft are in spacecraft.edb.

Several comets are in comets.edb and comets2.edb.

A few old sets of Shuttle elements are in shuttle.edb just to serve as a
handy example for an earth satellite to try out.

VLA radio calibrator sources for several wavelength bands are in vla*.edb.

Finally, I have the entire SAO database from NSSDC broken down into 10
files in ephem format. There are a total of 258,997 entries. The complete
set is 11,332,256 bytes, 3,034,691 compressed. Look on iraf.noao.edu in
contrib/xephem/SAO.

The xephem database format remains compatible with ephem v4.28 EXCEPT that
ephem requires entries to start with an alpha character. Either add one to
all such entries in this db or modify the function nxt_db() to allow a
leading digit as well (isn't having source nice?). And, of course, ephem
does not support the earth satellite object type, E. In general, see the
Help for Objects/Data Base for a full description of the xephem database
file format. A summary is repeated here for convenience.

Format summary:

  name,type, then as follows:
 
  fixed format:
     RA, hours
     Declination, degrees
     magnitude
     reference epoch, optional, assumed to be 2000 if absent
     s = angular size, arc seconds, optional
 
  elliptical format (e < 1):
     i = inclination, degrees
     O = longitude of ascending node, degrees
     o = argument of perihelion, degrees
     a = mean distance (aka semi-major axis), AU
     n = mean daily motion, degrees per day (computed from a**3/2 if omitted)
     e = eccentricity,
     M = mean anomaly (ie, degrees from perihelion),
     E = epoch date (ie, time of M),
     D = the equinox year (ie, time of i/O/o).
     g/k or H/G = magnitude model; select which by preceding the first field
 
  hyperbolic format (e > 1):
     T = epoch of perihelion
     i = inclination, degrees
     O = longitude of ascending node, degrees
     o = argument of perihelion, degrees
     e = eccentricity,
     q = perihelion distance, AU
     D = the equinox year (ie, time of i/O/o).
     g/k = magnitude model
     s = angular size at 1 AU, arc seconds, optional
 
  parabolic format (e == 1):
     T = epoch of perihelion
     i = inclination, degrees
     o = argument of perihelion, degrees
     q = perihelion distance, AU
     O = longitude of ascending node, degrees
     D = the equinox year (ie, time of i/O/o).
     g/k = magnitude model
     s = angular size at 1 AU, arc seconds, optional
 
  Earth satellite format:
     Epoch
     inclination, degrees
     RA of ascending node, degrees
     eccentricity, must be < 1
     argument of perigee, degrees
     mean anomaly, degrees
     mean motion, revolutions/day
     orbit decay rate, revolutions/day^2
     integral reference orbit number at Epoch
