Atlantis is scheduled to lift off at 4:34. Fortunately for us, December 6 is when the sun sets the earliest here in New York City, at 4:29 PM. The shuttle will become visible from New York at around 4:42PM, just as the sky is getting dark. If weather conditions are right we'll see a bright starlike object -- glowing both from reflected sunlight AND the exhaust from its rocket engines -- zoom across the deepening twilight sky from the southwest. The shuttle will arc across the southern sky and then head southeast, reaching an altitude of about 8 degrees (about two extended fists) above the horizon. If all goes well we might actually see the shuttle's engines cut off! The whole thing takes about 90 seconds from first visibility to last.
If people are interested I'd like to get a group together to see this. We'll need a place with a great panoramic southern view. I'm thinking maybe the beach/boardwalk at Coney Island, or Columbia University's Rutherford Observatory (if we can convince them to open it), or even the middle of the Brooklyn Bridge!
Of course, there are dozens of things that can prevent us from seeing the shuttle fly past New York. The launch might be postponed for weeks. The launch can be aborted that day, anywhere up to 30 seconds before ignition. The sky could be overcast. The sky could be perfectly clear except for a cloudbank over the southern horizon. Its a risk we have to take, but having seen the shuttle fly past New York before, I'd say the view is worth it.
Let me know if you are interested!