NAME: 
  lst2jd
 PURPOSE: 
  Compute UT given local sidereal time, longitude and approximate time.
 DESCRIPTION:
  This routine is based on the algorithms from p. 39 of "Astronomical
  Formulae for Calculators" by J. Meeus.
 CATEGORY:
  Astronomy
 CALLING SEQUENCE:
  lst2jd,jd0,lon,sidtim,jd
 INPUTS:
  jd0 - Julian Date (double precision), at 0h UT, scalar or vector.
          The "fractional" part of the jd is ignored.
  lon - West longitude of observatory in radians (scalar).
  sidtim - Local sidereal time (radians).
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
 OUTPUTS:
  jd     - Julian Date that matches sidtim.
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  2002/09/03 - Written by Marc W. Buie, Lowell Observatory