The Unicorn is a faint constellation in the lower half of Winter Hexagon. Its brightest star shines at only 3.9m, but the constellation makes up for the lack of distinctive stars with a variety of deep-sky objects.
M 50 is a 2,900 light-years distant open cluster, whose light is attenuated about one order of magnitude by dust clouds. Therefore, most of its stars blur into a shimmering patch of light between Sirius and Procyon, in which about half a dozen stars are embedded. One of these stars shines clearly red. If you start at Sirius and go to Procyon, you‘ll find M 50 after about a third of the way. The 100 to 150 million year old star cluster has a diameter of 16 arcmin, which corresponds to about 14 light-years.
The 5.0m bright star 5 Monocerotis is the brightest sun in the loose open cluster NGC 2232, whose 20 members are spread over a 10 × 30 arcmin large area – almost the size of the full Moon. Since the cluster is too broad for many telescopes, it is not mentioned in many star charts. Most of its stars have eighth to tenth magnitude and concentrate into two loose groups. The 1,300 light-years distant star cluster is still quite young with an age of 20 million years.
NGC 2244 is a loose cluster with about 20 minutes of arc in diameter, which is difficult to distinguish from the Milky Way stars. The 5.8m bright 12 Monocerotis is a good help when looking for the cluster, although this only 520 light-years distant star stands in no physical relationship to the approximately 5,000 light-years distant open cluster. NGC 2244 contains about 40 stars that are still embedded in the Rosette Nebula, from which they originated some 500,000 years ago. About a dozen stars reach seventh to tenth magnitude and can be resolved in binoculars, while the Rosette Nebula itself remains mostly invisible. Only with averted vision you may be able to glimpse it. Anyway, you need a truly dark sky to spot it with a pair of 10 × 50 binoculars. The Nebula is very large with 60 × 80 arcmin and has a low surface brightness. In reality, it has a diameter of 90 light-years, so that it is three times as large as the visible part of the Orion Nebula.
The Christmas Tree Cluster NGC 2264 is also a combination of a very loose star cluster and an emission nebula. It forms an arrow-like structure around the about 4.7m bright variable star S Monocerotis. The 30 arcmin large star cluster can already be partially resolved in 10 × 50 binoculars and shows around 20 stars. Several hundred fainter stars remain hidden in binoculars. The 20 light-years large Christmas Tree is facing south and is 2,600 light-years away from us. The nebula, in which the cluster is embedded, remains invisible. Even the famous Cone Nebula near the tip of the star cluster is visible only in photographs.
Harrington 5 is a seven arcminutes large triangle of six stars of eighth magnitude, which form an arrow pointing to the north. The asterism is located 3.5° southeast of β Monocerotis and almost exactly 7.5° north of Sirius. A large triangle of 5 to 6m bright stars can help you to find it – Hrr 5 is located on the northwest tip of this about 1° wide triangle.