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Observing Messier 81 (M81)
Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a grand design spiral galaxy about 12 million light-years away in the constellation Ursa Major. It has a D25 isophotal diameter of 29.44 kiloparsecs (96,000 light-years).
What Messier 81 is
Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a grand design spiral galaxy about 12 million light-years away in the constellation Ursa Major. It has a D25 isophotal diameter of 29.44 kiloparsecs (96,000 light-years).
How to observe it
This target is within reach of a small telescope of 70 mm to 130 mm from a reasonably dark site. More aperture and darker skies show more of its structure.
It lies in the constellation Ursa Major. To find it, learn the constellation first, then star-hop from its brighter stars with a finder or a wide-field eyepiece before switching to more magnification.
Magnification is your telescope's focal length divided by your eyepiece's focal length. For an extended object like this, start low to frame it, then step up in power only if the object takes it. Use the Fit My Telescope tool to see the exact magnification, true field and exit pupil each of your eyepieces gives.
How it looks at the eyepiece
What you see at the eyepiece is fainter and less colourful than a photograph, because the eye takes in light in an instant while a camera builds it up over minutes. Expect a grey glow rather than the vivid colours of an image, and let your eyes dark-adapt for at least twenty minutes to see the most.
Frame it at low to medium power first with a wide true field, then step up the magnification only if the object stays sharp and the sky is steady. The Fit My Telescope tool shows the magnification, true field of view and exit pupil each of your eyepieces gives in your telescope, so you can pick the one that frames the object best.
| Property | Value |
|---|---|
| Object type | active galactic nucleus |
| Constellation | Ursa Major |
| Apparent magnitude | 6.9 |
| Catalogue | Messier 81 (M81) |
Object data from Wikidata (CC0) and standard Messier catalogues.
What magnification suits M81?
Open the Fit My Telescope toolSee the true field and exit pupil each eyepiece givesFind telescope eyepiece on eBayaffiliateRelated
Sources: Messier 81 (Wikipedia, CC BY-SA) ยท Wikidata (CC0)