M46 and NGC2438 Open Cluster and Planetary Nebula in Puppis

Uploaded 4/3/10

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 There are only a few clusters among tens of thousands in the sky that have such a prominent planetary nebula superimposed on them. This is the best example in the entire sky. M46 is a moderately rich cluster, spanning some 30 arc minutes of sky - equal in size to the full moon in angular extent. At 6.1 magnitude it is barely seen with the naked eye on a dark night, and contains over 100 known cluster members. There are two additional objects in this image superimposed on M46. Foremost is the small blue green planetary nebula (a dying star) NGC2438 just north of the clusters center seen here as a round object just below the center of the cluster. It is a bright 10th magnitude, and a whopping 64 arc seconds in size (large for a planetary). Its central star is 18th magnitude and not seen here in this image.

The color of the planetary nebula is teal with a red rim. This is from triple ionised Oxygen for the green and hydrogen for the reds. I could never get the color right with my CCD on this one. It always shot as blood red, probably because of the edges of the filters band pass was too close to the green emission lines. I am thrilled to get the actual color here!

The second superimposed object is an 18th magnitude galaxy, located a few ring diameters to the lower right of the nebula. Its recorded as a dull orange color in this image.

Optics: 8" f/4 Newtonian Astrograph w/Baader MPCC Coma Corrector Platform: Astrophysics AP1200 Camera: Hutech Modified Canon XTi @ ISO800 Exposure: 12 x 5m = 1 hour Location: Payson, Arizona Elevation: 5150 ft. Sky: Seeing 4/10, Transparency 9/10 Outside Temperature: 35F Processing Tools: Photoshop CS2, Images Plus 3.82 HOME GALAXIES EMISSION NEBS REFLECTION NEBS COMETS GLOBULARS OPEN CLUST PLANETARIES LINKS