CONTACT: Robert_Creager@LogicalChaos.org

Requirements:
Popt:     http://www.gnu.org/directory/libs/popt.html
CFITSIO:  http://heasarc.gsfc.nasa.gov/docs/software/fitsio/fitsio.html

The downfits program creates 2 fits files and primary image extension using
the file names given on the command line.

Usage: downfits [-n INT] [-m INT] [-c STRING] [-d STRING] [-s <0|1>] [--usage]
  -n, --naxis1=INT       Number of columns in the image (default: 2064)
  -m, --naxis2=INT       Number of rows in the image (default: 2037)
  -c, --ccd0=STRING      File name for data from CCD 0 (default: "ccd0.fits")
  -d, --ccd1=STRING      File name for data from CCD 1 (default: "ccd1.fits")
  -s, --signed=<0|1>     When 1, fits values will range from -32767 to 32768.
                         When 0, fits values will range from 0 to 65536.
                         (default: 0)

The actual data is read from the MARK IV ISA card, a byte at a time, with
even/odd 2 byte combos going to the two image array.  The entire data set is
read at one time, and then written at once to the fits files.  From reading
the FITSIO documentation, this appears to be the 'best' way to accomplish
this.

Example:

downfits -c hbr_1234567.fits -d hir_1234567.fits -s 1

Will create the two files name with signed values in the fits image extension.