How can I make a mask from an exposure file?
The tool dmimgthresh may be used to create a mask of an image, e.g. an exposure map.
Flatten all the values greater than 1 to 1:
unix% dmimgthresh infile=expfile.fits outfile=expfile_flat.fits cut=:1 value=1
Then cut the values less than 1 and set them to 0:
unix% dmimgthresh infile=expfile_flat.fits outfile=mask.fits cut=1 value=0
