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NGC 246
Planetary Nebula
NGC 246, PNG 118.8-74.7, PK 118-74.1, ARO 43
Integrated Visual Magnitude: 8
Apparent Diameter: 8.2'
Magnitude of central star: 12
Distance: 1600-2500 ly
Actual Diameter: 4-6 ly

Minimum requirements to view: 4-inch scope and dark skies

NGC 246 is a reasonably bright, 8th magnitude planetary nebula that was discovered by William Herschel. Fairly large as planetaries go, NGC 246 is of relatively low surface brightness. It usually appears as a faint, round glow. McNeil classifies this nebula as having an "irregular disk with traces of ring structure."

The central star is HIP 3678, which is responsible for creating the nebula as it puffs it's outer layers out into space. It has a 14th magnitude companion 3.8" distant at PA 129o. The distance to this star system is 2100 light years, as measured by HIPPARCOS. This distance implies an actual size of 6 light years for the surrounding nebulosity. That's one and a half times the distance from our sun to the nearest star. There are two other 11th magnitude stars that lie within its glow. These are probably foreground or background stars not associated with the nebula.

The view in a 6" at 50x. North is down and east is right.

Although visible in telescopes as small as 4 inches to a trained observer under dark skies, most observers will require at least 6" to see it's faint, diffuse glow. Don't use too much magnification as this planetary is relatively large. Start by looking for a conspicuous group of four 11th magnitude stars. Once the field has been located, use averted vision to look for a slight haze. Small scopes may only reveal the brighter western half of the nebula. The central portion typically appears much fainter than the image below shows.

I logged NGC 246 with my 18" f/4.5 Dob without a filter:

"166x -- Very cool! Like a large bubble. Two bright stars inside, one centered. One bright star appears at the edge. The edges of the nebula appear brighter than the inside, particularly near the star. Not much sign of structure except for a rather strange appearance -- more of an impression -- that I can only describe as eerie."
Millennium Star Atlas Vol I Chart 316
Sky Atlas 2000 Chart 10
Uranometria 2000 Vol II Chart 261