The Rosette Nebula is usually referred to as NGC 2237, though
it includes areas designated NGC 2238, 2239, and 2246. All of these
parts were discovered visually during the 18th and 19th centuries,
before photography revealed them all to be parts of one, very large
object. At the middle of the Rosette Nebula is the young (4 million
years) open star cluster NGC 2244, whose intense radiation is clearing
out the middle part of the nebula and is setting the rest of it aglow.
Though the star cluster is visible to the unaided eye, the nebula is
very difficult to see visually even with a telescope because it is both
dim and spread out (its diameter in the sky is twice that of the full moon).
Throughout the nebula one can see dark lanes of dust and black "Bok
Globules," condensing dust and gas in the first stages of new star
formation. The Rosette Nebula is seen in the constellation Monoceros,
just to the East of Orion. It is about 5000 light years away, and
130 light years in diameter.

This image won the January 2008 Digital Astrophotography Group "Group Challenge" photo contest


Image data:
Camera: Canon 350 XT (modified)
Exposure: ISO 800, 5 minutes x 14, plus 5 minutes x 24 through 7nm hydrogen-alpha filter
Telescope: William Optics 66mm ZS, 0.8x reducer/field flattener
(this image has been cropped from the original)