Obviously I'm in the minority in this discussion, and will simply say that I don't find it to be nearly as complicated as others are making it out to be. For what they're worth, the list of pairs I've used for estimating seeing is here: ftp://ftp.lowell.edu/pub/bas/dbls.fil ...and a file of estimates made mainly in the 1980s with the 7-inch guidescope attached to the 'Pluto Camera', which I made while taking plates with that instrument: ftp://ftp.lowell.edu/pub/bas/seeing.vis \Brian -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.