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Deepsky Top-100 (10): M 81 & M82

Spring is a great time for observing galaxies, but you have to go to a dark sky site, to really find and enjoy them. There are however a few galaxies that can be seen from my light-polluted, suburban backyard. M 81 and M 82 in Ursa Major are among my favorites. The problem is: finding them. If the transparency is good, I can find them with my 7 x 50 binoculars, or the 8 x 50 finder-scope. In my 15 x 80 binoculars I always find them. Here's how to locate M 81 and M 82.

M81 & M82

Finder chart for M 81/ M82. Limiting magnitude 7
Credit and copyright SkyTools 2 by Capellasoft

Click here to download a printable finder chart (PDF)

First locate the Big Dipper in Ursa Major. Start at Gamma (?) Ursae Majoris. From there draw an imaginary line through the bowl of the Big Dipper towards Alpha (?) Ursae Majoris. From Alpha, extend this line for a distance that is equal to the distance Gamma to Alpha. When you do this, looking through your finder-scope, you should be able to see M 81 as a very faint patch of light. M 82 is a bit harder to see, due to its lower magnitude.

M 81 and M 82 were discovered by Bode in 1774. That's why they are sometimes called "Bode's Nebulae". Both galaxies are members of the Ursa Major Galaxy Group, the second nearest galaxy group to our own local cluster, lying at a distance of 10 million light years.

On photographs, M 81's size is 24' by 13', almost as big as the Moon, but through an amateur telescope only half of the size can be detected. Its visual magnitude is 6.9 and its surface brightness is 13.0. The coordinates of M 81 are 09h55.6m RA and +69deg 04' DEC. At low powers, M 81 fits in the same field of view with M 82. They are only separated by 38'. M 82 has a visual magnitude of 8.4 and a surface brightness of 12.8. It's size is 12' by 5.6' but from my own backyard I only managed to see a small part of it, about 8' by 2'. M 82 lies at RA 09h 58.8' and DEC +69deg41'. Probably you will not see any details in both galaxies when observing from a suburban area with moderate light pollution.

What you do see when observing M 81 and M 82 through binoculars or telescope, is the different shapes of the two galaxies. M 81 is large spiral galaxy (type Sa or Sb), slightly elongated north-south, looking more or less like an oval patch of light, while M 82, a irregular galaxy (type I0), oriented east-west, looks like a large cigar shaped object. However, if you really want to see some details, you have to travel to a dark-sky site.

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