This is one of a pair of galaxies (the other is M82), and they can be seen in the constellation Ursa Major near the asterism "The Big Dipper." They are interacting through mutual gravatational force and have done so for the past billion years.
They come close about every 100 million years and their mutual gravitational forces cause distortions in each galaxy. That effect can be seen in the open spiral arms of M81 because it is oriented to have an open face to us. It is separated from M82 by about 150,000 light years and the two will eventually merge into a single galaxy in about a billion years. M81 is about 70,000 light years in width, making it 70% the size of our Milky Way galaxy. It is about 11 million light years from us.(Apod/Nasa.gov)
This is a composite image with the color data from my SBIG ST-8XME camera and the luminance data from Bill Mattil's SBIG ST-10XME camera. Bill was kind enough to let me use his data for this image.
It was an interesting project because Bill's luminance data was shot at .62 arcseconds/pixel and my color data at 2.2 arcseconds/pixel. The color data was aligned and scaled to the luminance data with Registar. This image is a good example of how luminance provides the detail in a LRGB image since the color data had very low resolution at 2.2 arcseconds/pixel.
Dates Taken:
April 4,5 and 6, 2008 - Color
Feb 21, 2009 - Luminance
Locations:
April 4, 5 and 6, 2008: Ft. Griffin State Historic Site, TX - Color
Feb 21, 2009: Ft. Griffin State Historic Site, TX - Luminance
Telescopes:
Takahashi TSA-102 f/8 - Color
RCOS 10" Ritchey-Chretien f/9 - Luminance
Mounts:
Takahashi EM-10 Temma 2, guided by ST-8XME in-camera guide chip
Astro-Physics AP900GTO guided by ST-10XME internal guide chip
Cameras:
SBIG ST-8XME NABG w/ CFW-9, Astrodon RGB - Color
SBIG ST-10XME w/ Astrodon Luminance filter - Luminance
Exposures:
Red 90 min; Green 80 min; Blue 100 min; all color binned 2X2; 5 min subs
Luminance 40 minutes; 5 min subs
Total LRGB: 5 hours and 10 minutes
Processing:
CCDStack, Registar and Photoshop CS2
