[Prev][Next][Index][Thread][Search][Objects]
(IAAC) Obj: M46, n2438 - Inst: Newt 20" f/5
[Noted a lot of new subscribers lately, but not much new activity yet. To
get things started, here's a post from a WONDERFUL session I had this
weekend. Looking forward to reading everyone else's observations! Clear
skies, Lew]
Observer: Lew Gramer
Your skills (Beginner, Intermediate, Advanced): Intermediate
Date and UT of Observation: 1997-1-10/11, 04:00 UT
Location: Topsfield, MA, USA (42N)
Site classification (urban, suburban, rural): semirural
Limiting magnitude: 5.9
Seeing: 2 - good
Moon up: no
Instrument: Newt Reflector 20" f/5 (dob)
Magnification: 70x, 210x, 360x
Filters used: None, OIII
Object: M46, n2438
Category: Open cluster and planetary nebula
Constellation: Mon
Data: mag 6.1, 10.1 size 27', 66" (halo: ?)
RA/DE: 7h42m -14o49m
Description:
A stunning field at any power, this beautiful open cluster also
reveals something highly unusual to careful observation: a bright
planetary nebula superimposed on the cluster! In dark enough skies,
the planetary is visible in even very small telescopes. From this
site, at medium power (210x), the open cluster revealed some 170
stars (!) mags 8-14, just filling a 20' field of view. The dimmer
stragglers tended to give the cluster a somewhat elongated shape,
stretching rougly E and W. Surprisingly, on this night n2438 was
best seen at lower power (70x) as a faintish circuluar haze to the
NNW of the center of the cluser, perhaps 10' out. Averted vision
clearly showed the darker center, and a hint of obliquity in the
brighter ring. With the OIII filter in place, the ring shape was
obvious to direct vision, slightly elongated to the SSE-NNW, with
a "corner" on the SSE edge of the ring. At higher power (360x)
withOUT the OIII, a (false) central star of the planetary could
be seen directly. It was difficult to pinpoint this at the center
of the nebula, as using an OIII to heighten the annular nebulosity
resulted in the loss of the "central" star to direct vision!
===============================================================================
Karen Simmons & Lew Gramer dedalus@alum.mit.edu http://www.tiac.net/users/lewkaren
===============================================================================