The Rosette Nebula is a very well known example of an emission nebula surrounding an open cluster. Its photograph has adorned many a book or slide show on astronomy. Situated in Monoceros, it can be an ellusive object unless the skies are very dark. Then it can be observed with as small as a 6" telescope. Low magnification provides the best view as the nebula is quite large.
The nebula has 2 NGC designations, 2237 and 2238. These designate 2 of the brighter regions. The cluster in the middle has its own designation, NGC 2244. In the telescope the cluster appears as 2 parallel lines of stars.