Monday, April 11, 2011

Messier 81 and Messier 82

These two galaxies, Messier 81 and Messier 82, are considered the finest "showpiece" galaxies in the northern hemisphere. Located in the constellation Ursa Major, both galaxies were discovered by Johann Elert Bode in 1774. The larger galaxy, Messier 81, is a spiral galaxy and is often referred to as "Bode's Galaxy," or "Bode's Nebula." Messier cataloged both objects in 1781.

Messier 82 is an unusual cigar-shaped galaxy. It is usually classified as an irregular galaxy, but a study in 2005 discovered evidence of spiral arms. Tidal forces from Messier 81 have compressed gas and dust in Messier 81's core, which has triggered a large amount of star formation. As a result, it is classified as a starburst galaxy. Messier 81 and Messier 82 are moving toward each other and will eventually merge into a single galaxy.

Messier 81 and Messier 82, Epsilon-200 on NJP mount, 14x240
This image was the first that I've taken with the Epsilon-200 in several months. The tracking issues on the NJP have been largely resolved, so I am able to take longer exposures. Longer exposures generate more noise in the images, though, and the improved tracking means that objects in the field of view move very little from one exposure to the next. As a result, the stacking software tends to see hot pixels (stuck sub-pixels) as "signal" instead of "noise."

1 comment:

  1. Glad you were able to get out, Rory. These are very nice. Nice to hear the mount is working for you. The image came out very well, whatever the processing problems your skills never let us see! I've had these two on my list for a long time. I hope I get a shot at them before they combine ;-) .