I would actually doubt that amateur or professional astronomers spend enough time in real darkness, and spend most of their existence in ordinary ways, so that the difference from the rest of the population is actually very small. Most "professional astronomers" are college teachers, so and do very little observing (the average I read somewhere was about one week of nights per year). And of course even those of us running telescopes are (no longer at least) standing around in the dark, but instead doing it from what looks very much like an office with a bunch of computer screens, maybe with somewhat subdued lighting. You could make a list of the long-term telescope operators, and maybe get a hundred of us worldwide, but even the ones I know or know of are a rather disparate bunch in terms of age and lifestyle, so it would be hard to find a common thread amongst us (from strict vegans like Rob McNaught in Australia to the legendary Chilean telescope operators who are quite hefty beef-eaters) apart from having spent an awful lot of nights since we were college age pushing telescopes around. There could well be other effects of funny sleep cycles and so on, but that seems to vary greatly amongst individuals, from little effect to greatly debilitating physio/psychological problems (that would probably be there even without staying up late). \Brian -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.