SYNOPSIS
imstack [,-vi/][,-o filename/][,-n num/] ,file1.fits file2.fits /... ,filen.fits/DESCRIPTION
Stack FITS or IRAF images into single FITS image-
or : imstack [-vi][-n num] @filelist
-i: Do not put FITS header in output file
-n num: Use each file this many times
-m: Write IRAF multispec file
-o name: Output filename
-v: Verbose
-x root: Make first file root, others extensions