M 46 is a rich open cluster in the constellation Puppis.
It covers an area in the sky just a bit smaller than the
full moon. This cluster is about 5400 light years from earth,
and is 300 million years old. Perhaps the most interesting aspect
of this cluster is the small planetary nebula (NGC 2438) which is
seen near the bottom of the cluster in this image. That nebula,
however is not part of the cluster itself, and is probably a
foreground object.

Image data:
Camera: Canon 350XT (modified)
Exposure: ISO 800, 2 minutes x 19
Telescope: 10" Schmidt-Newtonian, Baader MPCC, IDAS LPS filter