NAME:
  perser
 PURPOSE:
  Automated asteroid period search tool.
 DESCRIPTION:
 CATEGORY:
  Photometry
 CALLING SEQUENCE:
  perser
 INPUTS:
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
 OUTPUTS:
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
   Commands:
     c - choose new trial period with cursor from last pdm scan
     e - edit data, to mark as good or bad
     f - fit a parabola to the last pdm scan to determine best period
     g - set trial period
     h1 - hardcopy of all mags versus time
     h2 - hardcopy of all shifted mags versus time
     hl - hardcopy of phase lightcurve
     hs - hardcopy of PDM scan
     l  - compute Lobm-Scargle periodogram
     p1 - plot all mags versus time
     p2 - plot shifted mags versus time
     pt - plot all datasets versus time in separate windows
     pp - plot all data versus phase
     r  - change reference night
     sm - set relative shifts from nightly means
     sp - scan period
     v  - set relative shifts best fit give current period
     q  - quit
 MODIFICATION HISTORY:
   Written by Marc W. Buie, 96/10/18, Lowell Observatory
   99/07/23, MWB, added hp and hs options (hardcopies)
  2000/11/08, MWB, removed use of obsolete code constructs
  2002/09/03, MWB, changed Str_sep call to strsplit