From: utzoo!decvax!cca!Lynn.ES@PARC-MAXC@sri-unix Newsgroups: net.space Title: Re: Article-I.D.: sri-unix.1613 Posted: Wed Jun 2 16:10:58 1982 Received: Fri Jun 4 05:44:27 1982 The chemical content of any given comet determines how it forms a head and tail at various temperatures (and therefore at various distances from the sun). So the first time a comet is observed, we are taking a wild stab when we predict its behavior. Kahoutek was a first timer. Halley's is not; it was recorded as having been seen at most of its appearances for 2000 years. There is little doubt that Halley's will look spectacular under the proper viewing conditions. That does not include any metropolitan areas where you cannot see even one tenth of the stars because of lights and polution. It also does not, for this particular passage, include northerly latitudes where the geometry of earth/sun/comet will keep much of the spectacular time in local twilight or daylight. Go south and away from the cities, and excepting only for cloudy weather, you can be guaranteed a spectacular comet. /Don Lynn PS - Scientifically, Kahoutek was spectacular, because it was discovered early and so allowed a long period of data gathering, even though it did not end up nearly as bright as predicted.