Messier 46 and Planetary Nebula NGC2438
Messier 46 is an open star cluster located approximately 5,500 light years away in the constellation of Puppis. The cluster is around 300 million years old and contains up to 500 member stars within its diameter of 30 light years.
The cluster was discovered by Charles Messier on 19th February 1771. It is notable because of the planetary nebula NGC2438 that was discovered by John Herschel in 1833 and seems to lie within its boundaries near the bottom in this image. This is the remains of a very old star that has shedded its outer layers and become a faint white dwarf visible as the small blue point in the very centre of the nebula.
The planetary nebula has a different velocity through space than the cluster and is also closer to us at a distance of 3,000 light years, so it is not a true member of the cluster but just happens to lie in the same direction.
Date: 1st January 2013
Exposure: LRGB: 44:12:10:10m, total 1hr 16mins @ -27C
Telescope: 10" Serrurier Truss Newtonian f/5
Camera: QSI 683wsg with Lodestar guider
Filters: Astrodon LRGB E-Series Gen 2
Taken from my observatory in Auckland, New Zealand