Orion wheels into view this time of year bringing along tiny blisters of beautiful nebulae and knots of silver-blue stars. Trailing Orion to the east, you’ll find the faint constellation Monoceros (the Unicorn), which holds a treasure chest of its own superb deep-sky sights. Perhaps the most beautiful is the Rosette Nebula, an achingly beautiful blossom of glowing gas and dust where new stars are being born. While hard to see visually, even in large telescopes, the Rosette Nebula is an excellent photographic target, and it contains a fine young open cluster that’s easy to see in binoculars.
The Rosette is an immense nebula, some three times larger than the Orion Nebula and three times farther away. The nebula overlaps the star cluster NGC 2244 forming within. Here’s a map to help you find the nebula and cluster. Look towards the southern horizon if you’re in the northern hemisphere, and almost directly overhead if you’re south of the equator.
You won’t see the nebula in binoculars… just the cluster. But it’s a fine cluster. NGC 2244 is only a million years old, having recently formed inside the nebula. This gaggle of blue stars shines at magnitude 4.4, so you can see it without optics in dark sky, which is impressive because the stars are some 4,900 light years away. So they must be intrinsically quite bright.
As for the nebula itself… well it’s quite a bit harder to see. It was discovered piecemeal in the 19th century by observers with large telescope, including a 48-inch reflector. The nebula is therefore cataloged in pieces: NGC 2237, NGC 2238, and NGC 2246. These are all parts of the same star-forming complex, which, because of the non-uniform illumination and sinuous dust lanes, displays an astonishing degree of complexity.
Here’s a lovely image made by Terry Hancock at the Down Under Observatory that shows you the full glory of the Rosette Nebula:
An image of the Rosette Nebula (courtesy Terry Hancock). Click to enlarge.
You won’t need a 48-inch scope to see the Rosette. But you will need very clear sky and good relief from light pollution… it’s not an easy object to see. The nebula was barely seen with a 16-inch scope by Ottawa-based amateur Rolf Meier and Fred Lossing in the 1970’s. Others have spotted it with a 4 or 5-inch scope. And the eagle-eyed Stephen James O’Meara has– amazingly– reported seeing it with his unaided eye and in 7×35 binoculars. Good dark sky is essential. And make sure your eyes are fully dark adapted. An OIII or UHC filter may help, too.