M101 Galaxy NGC 5457 Pinwheel Galaxy in Ursa Major
| Telescope / Lens | TEC 140mm f/7 |
| Mount Type | Astro-Physics 1200 |
| Camera | ST10XME |
| Filters | Astro-Don LRGB |
| Film | CCD |
| Exposure | LRGB of 4 hours 20 minutes (L=10x20min.; color 5min. sub-frames) -20° C |
| Processing | CCDSoft, AIP4Win, CCDStack & Photoshop CS2 |
| Date | 7-25-2009 |
| Location | Snow Peak, 30 miles SE of Cottage Grove, Oregon 122° 52′ 35″ W 43° 31′ 21″ N |
| Conditions | 4670′ magnitude 6.0 Skies; Clear & Steady |
Galaxy M101 (NGC 5457) is located in the constellation Ursa Major (The Great Bear). This spiral galaxy, also called “The Pinwheel Galaxy”, is magnitude 7.86 and is 28.6′ x 26.5′ in size. This shows up well in medium sized scopes at a dark sky site. Galaxy M101 is 21 million lights years distant & 170,000 light years across with 1 Trillion stars. Discovered by Charles Messier March 27, 1781.
The longer you image this galaxy, more details continue to surface while arms continue to grow in size. The hundreds of background galaxies that are visible is astounding. This is because we are looking out and up from the central region of our own Milky Way Galaxy which obscures our view of space. I have estimated that some of these background galaxies are 20-50 times more distant.
M 101 is one of the best face-on spirals visible through amateur telescopes. This galaxy is comparable to the size of our own Milky Way Galaxy. M101 has 5 prominent companion galaxies: NGC 5204, NGC 5474, NGC 5477, NGC 5585 & Holmberg IV. The gravitational interaction of these have shaped M101