NAME:
  obsnight
 PURPOSE:   (one line only)
  Determine general details of a given night determined by Sun and Moon
 DESCRIPTION:
 CATEGORY:
  Astronomy
 CALLING SEQUENCE:
  obsnight,jd,obs,night
 INPUTS:
  jd - Julian date for a time near midnight, string or double
  obs - Observatory information, either an integer, string, or structure
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
 OUTPUTS:
  night - anonymous structure with information about the night
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  2016/02/05, Written by Marc W. Buie, Southwest Research Institute