NGC 2264 The Cone Nebula

NGC 2264 indicates a bright open cluster surrounded by a large system of diffuse nebulosities (the Cone Nebula) within the constellation of Monoceros.

In fact, the first feature that strikes you when exploring this area of the sky with binoculars is a group of about twenty blue stars, dominated by the star S Monocerotis, of magnitude between the fifth and ninth, arranged in a triangle, with the vertex pointing southwards, a feature that in the southern hemisphere (where the top appears upwards) makes it similar to a Christmas tree (the latter is the proper name of the cluster).

At the southern tip of the cluster, if you observe with a Newtonian telescope with the help of a filter, a nebula becomes evident, in the edge of which there is a dark cone-shaped patch with the tip pointing towards the top of the Christmas tree; this structure has made the cloud famous with the name of Cone Nebula. To the northwest of the cluster there is also a vast fainter nebulosity, clearly visible in the long exposure photos.