C/2006 M4 (SWAN)
JPL Small-Body Database Browser
http://ssd.jpl.nasa.gov/sbdb.cgi?ID=dK06M040;orb=1;cov=0
Classification: Hyperbolic Comet
SPK-ID: 1002407
(hyperbolic orbits I think are diagnostic of comets which are just passing through, iow, not originating in the Solar System)
As soon as I got home from church, I found this ping waiting for me; thanks. I see it will actually be in the head of Hercules after tonight, according to the star charts posted. Unfortunately I live on the east side of Kentucky's second-largest city, so light pollution is a potential problem. I saw a fuzzy spot or two that could be the comet, but I can't be sure this late. Maybe I will have better viewing conditions tomorrow.