Syntax: opim [ add | sub | div | mul | pow | log | ln | mean
                  | mdn | ade | abs | min | max | rol | ror ]
    (FITS file 1) (FITS file 2) ... (FITS file n) (result FITS )
   [const=] [-clobber] [-verbose] [-constfirst]
  
       Operates on FITS files.  Valid operations: add, sub,
       div, mul, pow, log, ln, mean, mdn, or ade.
  
     FITS header from file 1 will be used for result image.
  
     const=  : specify a constant to use in the operation
               (constant will be last in operation sequence.)
    -clobber : overwrite "result FITS file" with no query.
    -verbose : give more details (and check HIRES angles.)
 -constfirst : put the constant first in operation sequence.
               (e.g.  result = constant (operation) file .)
  
 Operations: add="+", sub="-", div="/", mul="*", pow="**",
      log="log base 10", ln="log base e", mean="calculate
      mean value", mdn="calculate median value"
      ade="add error images in quadrature"
      abs="take absolute value of data"
      min="clip data at a minimum value given by const= "
      max="clip data at a maximum value given by const= "
      rol="Rotate image 90 degrees left (counter-clockwise).
      ror="Rotate image 90 degrees right (clockwise).
        ( "ror" and "rol" work for square images only.)