NGC 2264 is a large and scattered cluster easily visible in finder scopes and binoculars. It is composed of about 20 bright stars arranged in a pattern that resembles a Christmas tree, which measures half a degree long. The “tree” is seen upside-down in the sky, but is reinverted by most astronomical instruments. Because of its large size, low power is needed to see the entire cluster in a single field of view.
To find the Christmas Tree Cluster start from the 3rd-magnitude star Xi Geminorum, and then move three degrees to the south. Once you’re there take a close look at the cluster. Can you see the triangular shape that resembles the tree?
You will also notice a brighter star that stands out from the others. This is the giant S Monocerotis, a variable star that fluctuates only slightly between magnitudes 4.2 and 4.6.
Long-exposure photographs show faint nebulosity surrounding NGC 2264. At its southern edge is the famous Cone Nebula, a very faint haze around and to the south of the star V427 Monocerotis. Only a few observers can claim to have spotted the nebula visually, however the rest of us will always have the magnificent photographs like the one to the right.
Finder map – field width 15 degrees, stars to magnitude 9.