| Planetary
Nebula
aka PNG 231.4+04.3, PK 231+04.1 Integrated Visual Magnitude: 14-15 Apparent Diameter: 30" Distance: 8400 ly Minimum requirements to view: 14-inch scope, OIII filter and very dark skies |
The
open cluster M46 is famous for the fine planetary nebula that lies superimposed
upon it. But did you know that another planetary lies a mere 30'
north of the cluster center? Minkowski 1-18 is small and faint, and
few people know about it. Without an OIII filter it is out of reach
of even an 18-inch telescope under dark skies. But the OIII (and
UHC) have brought this planetary within reach of larger amateur instruments.
It's not clear what the minimum aperture is required to see it, but based
on my observations I'd say that it should be detectable in a 14-inch scope,
if not a 12 inch. It should be a real treat for those with access
to 20-inch or larger scopes.
Here is my log entry from January 2001 with my 18-inch f/4.5:
With the OIII in place M 1-18 became readily apparent at 166x and just bright enough to sustain 430x with averted vision. It appeared round and very diffuse; no obvious structure was seen. I had the impression at times of a fairly sharp, slightly ragged, edge. With the OIII removed I saw nothing.
The field in an 18-inch at 94x. M46 is at the top with NGC 2438 marked as a green oval. North is down and east is to the right.
| Millennium
Star Atlas Vol I Chart 295
Sky Atlas 2000 Chart 12 Uranometria 2000 Vol II Chart 274 |
