NGC 2264 indicates a bright open cluster surrounded by a large system of diffuse nebulosities, within the constellation of the Unicorn.
In fact, the first striking feature 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 pointed towards the south, a feature that in the southern hemisphere (where the top appears to be pointing upwards) makes it similar to a Christmas tree (the latter is the proper name of the cluster).
In the southern apex of the cluster, if observed with a Newtonian telescope with the aid of a filter, a nebula becomes evident, in the edge of which there is a dark patch in the shape of a cone with the tip directed towards the apex of the shaft of Christmas; this structure has made the cloud famous with the proper name of the Cone Nebula. A vast fainter nebulosity also extends to the northwest of the cluster, clearly visible in long-exposure photos.
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Optolong Blue 2″: 19×300″(1h 35′) (gain: 100.00) f/7 -10°C bin 1×1
Optolong Green 2″: 19×300″(1h 35′) (gain: 100.00) f/7 -10°C bin 1×1
Optolong H-Alpha 3nm 2″: 21×600″(3h 30′) (gain: 100.00) f/7 -10°C bin 1×1
Optolong Luminance 2″: 30×300″(2h 30′) (gain: 100.00) f/7 -10°C bin 1×1
Optolong OIII 3nm 2″: 25×600″(4h 10′) (gain: 100.00) f/7 -10°C bin 1×1
Optolong Red 2″: 19×300″(1h 35′) (gain: 100.00) f/7 -10°C bin 1×1