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NGC 2242

Planetary Nebula
aka NGC 2242, PN G170.3+15.8
RA: 06h34m07.4s Dec: +44°46'37" (Auriga)
Integrated Visual Magnitude: 14.5

Magnitude of central  star: 17.6
Angular Diameter: 22"
Mean Surface Brightness: 20.9 Mag/arc-secē

Minimum requirements to detect: 10-inch? under dark skies

NGC 2242 is a faint, little-known planetary nebula in Auriga that provides a nice challenge for users of larger telescopes.  This planetary nebula is considered to be a "galactic halo object" which lies high above the galactic plane.  It has also been found to be extremely hot with a subsequent high degree of ionization as compared to most planetary nebula.  The ionization state is critical to the success of UHC and OIII filters; too high or too low and these filters will not enhance the visibility of the object being viewed.

According to Shaw and Bidelman (1987PASP...99...27S), "The nebula NGC 2242 was discovered in 1886 November 24 by Lewis Swift (1887) at the Warner Observatory in Rochester, N.Y., with a 16-inch (41-cm) refractor."  He described the nebula as, "exceedingly faint, very small, and round."  Long thought to be a galaxy, it was Shaw and Bidelman who determined in 1987, some 100 years after discovery, that NGC 2242 is in fact a planetary nebula. 

The integrated visual magnitude is listed as 14.5, but don't let that stop you.  The surface brightness indicates that NGC 2242 should be readily visible in mid-sized (perhaps as small as an 8-inch) telescopes.  My impression is that the truth lies somewhere in between these extremes (it may perhaps be visible in a 10-inch).

NGC 2242 was not visible in my 18-inch at 97x.  At 260x it appeared, looking like a round, hazy, diffuse glow.  In my log entry one word sort of sums up what I saw, "indistinct."  No sign of a central star was seen.  As expected the OIII filter does not enhance the view.  In fact, it killed it completely as did the H-Beta filter.  Interestingly, Kent Wallace reports "Good response to the O-III and UHC filters" in his 20-inch.  It may well be that these filters are more useful with apertures of 20-inches or larger.


The field in an 18-inch at 95x.  North is down and east is to the right.
Millennium Star Atlas Vol I Chart 90
Sky Atlas 2000 Chart 5
Uranometria 2000 Vol I Chart 67
Herald-Bobroff Astroatlas B-05 C-22