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Observing Triangulum Galaxy (M33)
The Triangulum Galaxy is a spiral galaxy 2.878 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC 598.
What Triangulum Galaxy is
The Triangulum Galaxy is a spiral galaxy 2.878 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC 598. With the D25 isophotal diameter of 18.74 kiloparsecs (61,100 light-years), the Triangulum Galaxy is the third-largest member of the Local Group of galaxies, behind the Andromeda Galaxy and the Milky Way.
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 Triangulum. 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.
The object in NASA imagery
NASA has imaged this object. One example in the NASA Image and Video Library is titled Triangulum Galaxy Imaged by Herschel, Planck, IRAS, COBE, from JPL.
This image of the Triangulum galaxy, or M33, includes data from the ESA (European Space Agency) Herschel mission, supplemented with data from ESA's retired Planck observatory and two retired NASA missions: the Infrared Astronomical Satellite (IRAS) and Cosmic Background Explorer (COBE). Operated from 2009 to 2013, Herschel detected wavelengths of light in the far-infrared and microwave ranges, and was ideal for studying dust in nearby galaxies because it could capture small-scale structures in the dust clouds in high resolution.
NASA imagery is in the public domain. What you see through an eyepiece is fainter and mostly grey, since the eye does not accumulate light the way a long-exposure camera does, but knowing an object's true shape helps you recognise it at the telescope.
| Property | Value |
|---|---|
| Object type | flocculent spiral galaxy |
| Constellation | Triangulum |
| Apparent magnitude | 5.7 |
| Catalogue | Messier 33 (M33) |
Object data from Wikidata (CC0) and standard Messier catalogues.
What magnification suits M33?
Open the Fit My Telescope toolSee the true field and exit pupil each eyepiece givesFind telescope eyepiece on eBayaffiliateRelated
Sources: Triangulum Galaxy (Wikipedia, CC BY-SA) · Wikidata (CC0) · NASA Image and Video Library: PIA25165 (public domain)