Comet 46P First Attempt

Last night I had intermittent cloud with some nice clear patches so I figured that I’d have a crack at capturing comet 46P / Wirtanen as it’s only a couple of days away from it’s closest approach to Earth. 46P is a small short period comet, with an orbital period of 5.4 years, and was the original destination for the Rosetta spacecraft. It is currently passing between Aldebaran and Messier 45, so should be easy to locate…so I thought. The evening ended up as a complete disaster….

During the process of setting up and polar aligning my rig (ST102T mounted on the SW SA) I managed to stand on the USB cable supplying power to the mount. This had the rather unfortunate effect of snapping the port from it’s position and causing it to drop down into the mount body. Subsequent investigation after the fact makes me think it will be an RTB (return-to-base) for repair. Consequently in the meantime she’ll be running on battery power. Maybe I should take out shares in Duracell…

Unfortunately, by the time I’d sorted out the mount and replaced the batteries, cloud had come between Aldebaran and M45 and didn’t show any signs of letting up. Orion however was still clear, so I opted for having a go at capturing M42. The camera (Nikon D5300) battery was also running low by this point as I’d been running Live View up to this point and in the cold weather it was draining fast. On the plus side, I’d managed to set my focus successfully at least.

As I wanted to image SOMETHING at least, I had a crack at M42 with what was left of my battery power, and still with cloud threatening to obscure my Plan B. The image below is the result of 35 subs, with no calibration frames, totalling only 11.6 minutes of usable data at ISO 800, before both cloud rolled in and the Nikon battery died. I’m very much liking the 500mm focal length of the ST102, although even stopped down to about f / 9.5 there’s still a fair amount of chromatic aberration on the brightest stars. With more data plus calibration frames, I think M42 is going to look pretty damn good. The image was cropped only for vignetting.