UPDATE #2: It's not a comet, it's a fuel dump from a classified rocket launch.
On the CCD mailing list:
I just went outside and there is at least a mag 2 comet visible at the zenith. I don’t think this is Holmes….Get outside now!!!
Is it Comet Holmes outbursting short of 60 days later?
UPDATE: On the AAVSO mailing list, someone pins it down to Lacerta, and probably gets it right (satellite fuel dump):
I just went out at 00:00UT on Dec 11 UT. I looked up and in Lacerta directly between Cygnus and Cas was a large, bright diffuse object, looking similar to a comet. I'm talking bigger than Comet Holmes and probably 2nd mag. I got my 10X50 binocs and checked it out. It is slowly moving past the stars to the NE. It has a bright pin-like jet toward the NW, which can be seen unaided eye. The only thing I can figure out is that this was ejected from a satellite/rocket as some upper atmosheric experiment. It was out there as of 5 miutes ago. Anyone see it??? Any ideas on what it is???
Chris Stephan SET
Robert Clyde Observatory
184 Orday Rd.
Sebring, FL. 33875