NAME:
  objstars
 PURPOSE:
  Get a list of stars from the USNO A2.0 catalog centered on a solar system object.
 DESCRIPTION:

 CATEGORY:
  Astronomy

 CALLING SEQUENCE:
  objstars,starttime,ndays,objcode,outfile,OBSCODE=obscode,PAD=pad

 INPUTS:
  starttime - Starting time for object ephemeris.  This can be provided as
                a julian date (scalar), or a 3,4,5, or 6 element time vector
                [y,m,d,h,m,s].  h, m, s, are optional in order of decreasing
                significance.
  ndays     - Number of days to run ephemeris over.
  objcode   - Object code for solar system object (see EPHEM.PRO)
 OPTIONAL INPUT PARAMETERS:
  outfile   - Output file name, default is objcode+'.'+FILETYPE
 KEYWORD INPUT PARAMETERS:
  FILETYPE  - Specifies the output format for the file.  This type is also
                used as the default suffix of the output file name.
                edb - (default) ascii format needed for XEphem.
  OBSCODE   - Standard M.P.C. observatory code, default is geocentric
  PAD       - padding distance around path of object for extraction,
                default = 240 arcsec
 OUTPUTS:

  A file is created that is in the format specified.

 KEYWORD OUTPUT PARAMETERS:

 COMMON BLOCKS:

 SIDE EFFECTS:

 RESTRICTIONS:
  It is not practical to extract too large of a list.  Also, this program
    does not have appropriate logic to handle the case where the object's
    path crosses 0h RA.  There is an arbitrary limit of 2 degrees placed
    on the extraction widths to prevent extracting the entire star catalog.

 PROCEDURE:

 MODIFICATION HISTORY:
  Written by Marc W. Buie, Lowell Observatory, 1999 July 13
  2002/09/09, MWB, added support for string obscode values
  2003/10/01, MWB, converted my Delfile call to system file_delete routine