Name
       extract_spec - extract a spectrum

Synopsis
       extract_spec -i infile [options] [-o outfile]

Description
       extract_spec extracts an horizontal spectrum from an image and subtract
       to it an estimation of the sky contribution.  This  sky  estimation  is
       done  using  a  background  zone that can be specified by the user. The
       user can also specify the spectrum width. The spectrum position in pix-
       els has to be specified by the user.

       The extracted spectrum is displayed with gnuplot.

Options
       -p pos or --spec_p pos
              pos  is  the  spectrum position in pixels, 1 being the bottom of
              the image.

       -w width or --spec_w width
              Spectrum width in pixels.

       -d dist or --sky_d dist
              dist is the gap in pixels between the spectrum and the zone used
              to estimate the background.

       -W width or --sky_w width
              width  is  the  width of the zone used to estimate the backgound
              (use 0 if you do not one any background correction).

       -n or --nograph
              This flag is to be used to switch the plot off.