Turn up the brightness on your monitor and you can see the other rings. A central obstuction will throw more light into the other rings. Jack Jones > only one ring. With my 12.5" Dall-Kirkham I see four or more at the > highest magnification I can get with my eyepieces. Either this indicates -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.