This is very hard to picture and even harder to describe. It is two transparent bowls sitting inside eachother. You turn them just like you do the two parts of a planisphere. It is 14" wide and 8" deep. It is the Halley's Comet Commemorative Edition and shows the path of Halley through the sky. The condition is like new.
The non-Commemorative editions sold under the title "Bowl of Night" for $65 in the early 80's.
I do not plan to keep this, so let's say $50 shipped or best offer, feel free to make one.