M81 or Messier 81 (also known as NGC 3031 or Bode’s Galaxy) is a grand design spiral galaxy about 12 million light-years away, with a diameter of 90,000 light years, in the constellation Ursa Major. Due to its proximity to our galaxy, large size, and active galactic nucleus (which harbors a 70 million supermassive black hole), Messier 81 has been studied extensively by professional astronomers. The galaxy’s large size and relatively high brightness also make it a popular target for amateur astronomers.
Messier 81 was first discovered by Johann Elert Bode on 31 December 1774. Thus, it is sometimes referred to as “Bode’s Galaxy”. In 1779, Pierre Méchain and Charles Messier reidentified Bode’s object, hence listed it in the Messier Catalogue.
The galaxy is to be found approximately 10° northwest of Ursae Majoris (Dubhe) along with several other galaxies in the Messier 81 Group. Its apparent magnitude due to its distance means it requires a good night sky and only rises very briefly and extremely low at its southernmost limit from Earth’s surface, about the 20th parallel south.
Messier 81 and Messier 82 are considered ideal for viewing using binoculars and small telescopes. The two objects are generally not observable to the unaided eye, although highly experienced amateur astronomers may be able to see Messier 81 under exceptional observing conditions with a very dark sky. Telescopes with apertures of 8 inches (20 cm) or larger are needed to distinguish structures in the galaxy.
Most of the emission at infrared wavelengths originates from interstellar dust. This interstellar dust is found primarily within the galaxy’s spiral arms, and it has been shown to be associated with star formation regions. The general explanation is that the hot, short-lived blue stars that are found within star formation regions are very effective at heating the dust and thus enhancing the infrared dust emission from these regions. (*Source: Wikipedia)
The image above, I took during several nights in March & April of 2021. This target comes at 81° max height in my region. I photographed it with different exposures without using a filter and different exposures with a UV/IR Cut filter. Just to test some things out but all the frames that were good, I kept and stacked them. I also tried to keep the colors as natural as possible. At the outer spiral arms, you can see that some blue color is already coming through if you look good at it. Total exposure time is 11hrs 55min. Hopefully, beginning next year, I’ll get the chance to visit this target again and add more data to this image. With more integration time, I could get more red and blue out of it in processing.
Image details
- Telescope: Sky-Watcher Explorer Black Diamond N200/1000
- Mount: iOptron CEM60 on iOptron tri-pier
- Camera: ZWO ASI 294MC Pro
- Filter: ZWO UV/IR Cut filter 1.25″ (ZWO EFW Mini)
- Telescope control: ZWO ASIair gen.1
- Software: Astro Pixel Processor (stacking & processing); DPP4 (Canon software, little finishing touch)
No guiding, no coma corrector
Data captured on the following nights: 02/03/2021; 06/03-07/03/2021; 03/04-04/04/2021 & 22/04-23/04/2021
Total integration time: 11hrs 55min
SQM-L: 19.41 (average) -> Bortle class 6
