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Observing Orion Nebula (M42)
The Orion Nebula is a diffuse nebula in the Milky Way situated south of Orion's Belt in the constellation of Orion, and is known as the middle "star" in the "sword" of Orion. It is one of the brightest nebulae and is visible to the naked eye in the night sky with an apparent magnitude of 4.0.
What Orion Nebula is
The Orion Nebula is a diffuse nebula in the Milky Way situated south of Orion's Belt in the constellation of Orion, and is known as the middle "star" in the "sword" of Orion. It is one of the brightest nebulae and is visible to the naked eye in the night sky with an apparent magnitude of 4.0. It is 1,267.0 ± 5.4 light-years (388.5 ± 1.7 pc) away and is the closest region of massive star formation to Earth. M42 is estimated to be 25 light-years across. It has a mass of about 2,000 times that of the Sun. Older texts frequently refer to the Orion Nebula as the Great Nebula in Orion or the Great Orion Nebula.
How to observe it
This is a naked-eye or binocular object under a dark sky. Any telescope shows it, and a low-power, wide-field eyepiece gives the most pleasing view.
It lies in the constellation Orion. 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.
This object is the brightest nebula in the sky, visible to the naked eye below Orion's belt, which makes it a rewarding target once you have found it.
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 Orion Nebula and Bow Shock, from JPL.
Astronomers using NASA Hubble Space Telescope have found a bow shock around a very young star in the nearby Orion nebula, an intense star-forming region of gas and dust.
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 | H II region |
| Constellation | Orion |
| Apparent magnitude | 4.0 |
| Catalogue | Messier 42 (M42) |
Object data from Wikidata (CC0) and standard Messier catalogues.
What magnification suits M42?
Open the Fit My Telescope toolSee the true field and exit pupil each eyepiece givesFind telescope eyepiece on eBayaffiliateRelated
Sources: Orion Nebula (Wikipedia, CC BY-SA) · Wikidata (CC0) · NASA Image and Video Library: PIA04227 (public domain)