NAME: 
  photred
 PURPOSE: 
  Reduction of non-variable point source absolute photometry.
 DESCRIPTION:
 CATEGORY:
  Photometry
 CALLING SEQUENCE:
  pro photred,stand,fil,jd,am,serial,mag,err,comp,dofil, $
           object,redmag,rederr, $
           NOPRINT=noprint, PLOT=plotit, BINFAC=binfac, FORCE=force
 INPUTS:
  stand  - String array of standard names.  (See coord.)
  fil    - String array of filter names for observations.
  jd     - Double precision array of Julian dates.
  am     - Floating point array of the airmass of observations.
  serial - Serial number of observation.
  mag    - Raw instrumental magnitudes.
  err    - Uncertainties on the raw magnitudes.
  comp   - Standard name of comparison star.
  dofil  - Name of filter to reduce.
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
  ALL     - Flag, if true reduces non-stars as well and returns a single
              average value for non-stars.
  BINFAC  - Maximum amount of comparison star point to bin (default=6)
  FORCE   - Two element vector that contains override values for the
              mean extinction and its uncertainty.  This replaces the
              initial fit for mean extinction.
  NOPRINT - Flag, if true, will inhibit the summary printout to the screen.
  PLOT    - Flag, if true will enable the summary plot of the comp star.
  STDMAG  - Standard magnitude of comparison star (default=0).
 OUTPUTS:
  object - Name(s) of program object reduced against comp star.
  redmag - Final reduced magnitude of object compared to comp star.
  rederr - Final uncertainty.
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  1993/07/28 - Written by Marc W. Buie, Lowell Observatory
  1993/12/09 - MWB, added extinction override (FORCE)
  1993/12/12 - MWB, added ALL flag
  2009/10/02, MWB, changed Polyfitw call to poly_fit equivalent