Planetary Over M46 Open Cluster

Constellation: Puppis
Ra: 7hr 41m 50s
Dec: -14d 44m 5s
Distance: 2,900 light years
Image Size: 38' x 38'
North: Lower left



The ring-shaped mag. 10.8 planetary nebula, NGC2438 (Herschel H IV.39) is a 1.3′ dia. planetary nebula in the constellaiton Puppis that appears within the larger 20′, mag 6.1 open cluster, NGC 2437 (M46). NGC2438 is superimpsed on M46 but is not a member of the open cluster. It is 2,900 light years distant and was discovered by Herschel in 1786, whereas M46 is thought to be 300 million years old and is 5,000 light years distant. The bright star near the center of the nebula is not the proginator star, which is likely to be the adjacent small, bluish star that SEDS indicates is a mag 17.2 star. The planetary nebula color and detail were augmented with 1 hour of Astrodon 3 nm OIII and 1.3 hrs of 5 nm H-a. The OIII has the shape of a complete ring whereas Ha forms an horseshoe shape with the opening toward th north (lower left). There is an extended halo ~2.5′ in diameter surrounding NGC 2438 that is brought out by the narrowband data.

Exposure: 3.33 hrs Total: 1 hr RGB, 1 hr OIII, 1.33 hrs H-a
Telescope: 14.5" f/8.2 Classical Cass. in RCOS truss
Mount: Software Bisque Paramount ME
Oag: Astrodon MonsterMOAG
Acquisition: CCD AutoPilot4
Calibration: CCDStack2
Observatory Site: Riverland Dingo Observatory, Moorook, S. Australia
Camera: Apogee U16M
Filters: Astrodon 5 nm H-a, 3nm OIII, Gen 2 RGB
Guider: SBIG ST-402
Camera Operation: MaximDL5.08
Processing: Photoshop CS3
Image Date: 12/30/2009

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