Comet 21P/Giacobini-Zinner
Combination of 2, 200 second images, SBIG ST4 CCD.
300mm f/6 newtonian at prime focus.
Comet 21/p Giacobini-Zinner is a member of Jupiter's "family" of comets, with an orbital period of about 6.6 years. Perihelion distance of 1.04AU, while the aphelion distance is about 6.0AU. The comet was the first to be visited by a spacecraft, the International Cometary Explorer, which passed the comet on September 11, 1985.
Giacobini-Zinner is one of the brighter periodic comets, reaching about 7th magnitude during a favourable return. It was also the first comet I managed to successfully image with a CCD, back in 1998, when I was experimenting imaging with an ST-4. At the time this image was taken, the comet was around magnitude 10.3 and displayed a faint tail.