The description reads like the old Lumicon 'Deep-Sky' filter from the late-70s/early-80s that just cut out the mercury and night-sky lines, leaving the rest of the passband open. I would be surprised if the effect was more than a very modest increase in contrast on galaxies. \Brian -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.