MONOCEROS (pronounced moh-NOSS-er-us), the Unicorn

Chart showing Monoceros

Monoceros, the unicorn, has been attributed to Jakob Bartsch, a German mathematician, and son-in-law of Johannes Kepler, who brought it into general use on his star charts of 1624. However, it seems to have been formed much earlier, Scaliger having found it on a Persian sphere in the previous century. Its location in the Milky Way ensures that it is well stocked with nebulae and clusters.

To find Monoceros look towards the north to find the "Pot" of Orion. Find the bright stars Sirius and Procyon and look at the area between them.

Chart showing Monoceros as seen to the northwest about 10 pm towards the end of March.

When Monoceros is due north, rotate the chart clockwise so that Monoceros looks like an upright capital M.

Monoceros and surrounding constellations

Constellation Canis Major Constellation Puppis Constellation Hydra Constellation Canis Minor Constellation Cancer Constellation Gemini Constellation Orion Constellation Lepus

Details of some of the objects shown in the chart.

α Monocerotis is a magnitude 3.9 orange giant star 180 light years away.

β Mon is a beautiful white triple star. William Herschel discovered it in 1781 and thought it 'one of the most beautiful sights in the heavens'.

The smallest of telescopes should separate the three components of magnitudes 4.5, 5.2,and 5.6, on a good night. They form a curving arc of blue-white stars, the faintest two being closest together. There is evidence that one component is a spectroscopic binary, and as well a close speckle companion was discovered to another component in 1988. This is probably a quintuple star system.

δ Mon is a magnitude 4.2 blue-white star 210 light years away. It has a wide unrelated unaided eye companion of magnitude 5.5.

ε Mon is an easy double star for small telescopes, consisting of yellow and blue components of magnitude 4.3 and 6.7, 180 light years away.

M 50 (NGC 2323) is a large splendid open cluster of about 100 stars, visible in binoculars and small telescopes. Many of the stars are in pairs, triplets and small groups, while a bright orange star is close to the centre of the group.

NGC 2232 is a scattered irregular open cluster surrounding the 5th magnitude blue-white star 10 Mon. It is visible in binoculars and small telescopes.

NGC 2244 is a bright scattered cluster, lying mostly in a dark space around which is a large band of luminosity - the Rosette Nebula (NGC 2237/46). The cluster is visible in binoculars or small telescopes. Large apertures or an OIII filter are needed to be able to see the Rosette Nebula.

NGC 2261 is a fan shaped nebula known as Hubble's variable nebula. It has the variable star R Mon at the apex. Changes in its form have been observed for more than a century. These are partly caused by the variability of the star which varies between magnitudes 9.5 to 12

NGC 2301. This bright open cluster in a beautiful field is well suited for binoculars or small telescopes. There is an orange star in the roughly round central region.

NGC 2264 is a combination of star cluster and nebula. The cluster is visible in binoculars or small telescopes, contains about 20 members, including the 5th magnitude star S Mon - an intensely blue-white slightly variable star with a close companion. The nebula is known as the cone nebula, because of its tapered shape. It shows up well on long exposure photographs, but is visually very difficult to see, requiring a Hb filter


Monoceros straddles the celestial equator and can be viewed in the evening from the beginning of the year until early June. It is due north at about 11.30 pm in mid February and 2 hours earlier mid March. When due north, Monoceros is to the right of Orion and below Canis Major.