Yes, multiple `-k` parameters is what I had in mind.  There's no right or wrong way here though.  I think either is acceptable.  My only resistance to using a comma separator is that, unfortunately, commas are technically valid in some kinds of non-standard extensions to the keyword syntax that are supported by pyfits.  Not that I've ever *seen* them used in the wild though, so it's probably okay to make an exception.   It's just...unfortunate :)