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(IAAC) Re: M1-79

Subject: 
         Re: [Fwd: Fwd: Obj: M1-79 (PK93-2.1, png93.3-2.4) - Inst: 20"
f/5 dob]
   Date: 
         Sat, 19 Jun 1999 16:02:41 -0500
  From: 
         "Julian McNeil" <icnebula@primenet.com>
     To: 
         "Barbara Wilson" <bwilson2@ix.netcom.com>


Barbara,

   Minkowski 1-79 is indeed an interesting PN.  As you can see from the
DSS
image, the outer structure is very elongated ~E-W with much off-axis
stratification (esp. across the minor axis).  From a research point of
view, M 1-79 is typically classified as a Type I PN.  These normally
have
either very massive or binary progenitor central stars, and they are
almost
always associated with PNe having bipolar characteristics and/or quite
exotic outer envelopes (presumably from much interaction during the PPN
phase between the central star component(s) and the multi-speed
winds/material previously released).  Though contained in a recent paper
(not yet scanned onto ADS), I have yet to see any really nice high-res
images of this object.  I do, however, suspect that the nebula is
morphologically markedly similar to IC 4406 in Lupus, which happens to
have
basically the same elongated/stratified shape in really deep images.

   As you know, IC 4406 presents a wonderful E-W bipolar nebula (usually
over 1' in length) through moderately large scopes under good skies. 
However, it is my experience that smaller instruments (~10-inchers or
less)
and/or less favorable conditions only show the very core of this nebula,
which happens to consist of a relatively small (<30" in length) and
bright
"waistband" or torus of material oriented in a N-S manner.  Therefore,
under "not so good" conditions, even a larger instrument may only show
this
small "bipolar" nebular core oriented to the N-S!  In contrast, the same
instrument on a better night will show the nebula's fainter "true"
bipolar
nature with it's E-W orientation (and over 1' length) along with the
previously mentioned N-S oriented core nestled neatly at it's center. 
This
same contrast-effect can also usually be demonstrated by blinking the
nebula with a UHC/OIII filter, as the filter will easily bring out the
fainter bipolar wisps along the "true" major axis of the nebula and
therefore change the "apparent" elongation of the entire object!

   In short, I feel that this is probably what Lew is experiencing (just
on
a somewhat more difficult scale with M1-79).  He is probably just seeing
the nearly edge-on inner torus of rather dense material that creates the
overall E-W bipolarity of the nebula itself.  I suspect that the other
observers mentioned were probably observing the true E-W bipolar nature
of
the nebula, which would naturally appear at a right angle to the core
elongation and would also appear somewhat larger and more diffuse.  My
only
notes on this object are from 1994 using a 10" f/5 Cave.  At powers from
141x to 264x, it appeared quite small (<20") and very faint.  It did
react
to the OIII filter, however, the filter seemed to have made the
appearance
of the nebula more diffuse and amorphous.  Otherwise, I didn't note any
particular shape/orientation with the 10".  Either way, Lew's
observation
was quite nice and very informative.  Hope this helps...

Jay
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"Great spirits have often encountered violent opposition from mediocre
minds!!!"    ~Albert Einstein
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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