Thanks Robin,
Yes, I see there is an ‘Auto atmosphere’ button in the general tab in Isis but sparse documentation…
So, I think I’ll recycle IR data with care… I think if you separate the instrument components (camera and Alpy) and are working at quite different temperatures, you might want to be sure to use new IR data, but otherwise it looks OK. In addition I have discovered the comment field in FITs editing in BASS! (Homer Simpson moment here…). Suitable use therein should make it clear.
Cheers
Kevin