NAME:
  astsclbar
 PURPOSE:   (one line only)
  Draw a scale bar on an astronomical image.
 DESCRIPTION:
 CATEGORY:
  Astronomy
 CALLING SEQUENCE:
  astsclbar,pscale
 INPUTS:
  pscale - Image scale in arcsec/pixel
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
  THICK = changes thickness of line, default=2

  Recognizes all standard plot graphics keywords.
  
 OUTPUTS:
 KEYWORD OUTPUT PARAMETERS:
 CONFIGURATION:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  Written by Marc W. Buie, Southwest Research Institute, 2022/03/11
  2024/03/10, MWB, added case for very large FOV scale bars