How do I create a white-light image?

You can make use of the DATACUBE squash shell script which is a user friendly interface to the KAPPA collapse application allowing you to create both white-light and passband image, e.g.

   % squash -p
   NDF input file: ifu_file
         Shape:
           No. of dimensions: 3
           Dimension size(s): 59 x 110 x 961
           Pixel bounds     : 1:59, 1:110, 1:961
           Total pixels     : 6236890
           Wavelength bounds : 4526:10089.8

   Lower Wavelength-axis bound : 4526
   Upper Wavelength-axis bound : 10089.8

         Collapsing:
           White-light image: 59 x 110
           Wavelength range: 4526--10089.8 Angstrom

   NDF output file: out

         Output NDF:
           File: out.sdf
   %

Figure: The squash script.

Here we make a white-light image from the input data file ifu_file.sdf, saving it as a two-dimensional NDF file out.sdf as well as plotting it in a GWM window (see the figure).

Alternatively we can make use of scripts command-line options and specify the input and output files, along with the wavelength bounds, on the command line, as in this example.

   % squash -i ifu_file -o out -l 4526 -u 10089.8 -p

Alternatively we can make direct use of the collapse application.

   % collapse
   IN - Input NDF /@/tmp/aa_squash_collapse/ > ifu_file
   AXIS - The axis to be collapsed /'1'/ > 3
      Collapsing pixel axis 3 from pixel 1 to pixel 961 inclusive...
   OUT - Output NDF > out
   %

Here we collapse the cube along the third ($\lambda$) axis.