In a message dated 98-09-13 14:34:23 EDT, you write: Bob<< The light from a comet is simply reflected sunlight just like the light we see from the moon and the planets. It has nothing to do with ionization or the Earth's atmosphere. >> There is an Ionized tail and a dust tail. The dust tail reflects sunlight...and the ion tail produces the dim blue glow by emitting it's own light doesn't it? GeoZay