RE: (IAAC) Object: M42/M43 Instrument: 16" Newtonian f/4.59

Hi Todd:
	I believe light throughput does impact color perception when viewing
deep-sky objects, and can vary from person to person. It may also be
related to limiting magnitude and seeing conditions. For example, in
most of the telescopes I observed M-42 in it appeared as a bright green
color. However, when I began observing with a 6" f/9 AP refractor a
number of years ago it appeared more blue-green then green, and on one
night when the seeing conditions were quite good and limiting magnitude
was est 5.6 I saw a reddish tinge along the bottom of the nebula. On
nights where the seeing conditions and limiting magnitude were not very
good it appeared more it's usual green color with no hint of red along
the bottom. Noted similar results in my 20" Obsession, except of course
the colors were far more pronounced and vivid, and much more fine detail
was visible. So there may be a threshold of where the light throughput
from the telescope is strong enough to activate certain color receptors
in the eye, and once again it does seem to vary from person to person.
From: Todd Gross
To: netastrocatalog@atmob.org
Subject: (IAAC) Object: M42/M43  Instrument: 16" Newtonian f/4.59
Date: Friday, September 05, 1997 8:27AM
Observer:  Todd Gross
Your skill:  Intermediate
Date and UT of observation: 09/05/97 0815 GMT
Location & latitude: 22 miles west of Boston, Ma. 42.3N
Site classification: Suburban
Limiting magnitude (visual): 5.2 (estimated) 4.7 (est) in vicinity of
Seeing (1 to 10 - worst-best):  4-5
Moon up (phase?): No
Instrument: 16" Newtonian-dob w. 96/99% coatings
Magnifications: 98x, 210x, and 210x with binoviewer
Filters used: none and UHC
Object: M42/M43
Constellation: Orion
Object data:  Emission nebula
This is by far the best astronomical object in this scope. In fact, the
view is
so good, it far exceeds the beauty seen in photographs. The nebula is
a huge emission nebula with filamentary arms, clouds of gas, and dark
Separated by M43 by a broad, glow-free area. I will not try to describe
nebula in detail at this time. Here is an overview though.
In my slightly light polluted skies, the 19mm Panoptic at 98x brought
the best wide view. At first glance, the entire complex looked strong,
electric (radiant) blue-green ( a bit closer to green ). This is the
colorful object I have ever seen bar some doubles and perhaps Jupiter.
Color was best maintained at 98x, but was also seen clearly at 210x...
through the binoviewer, also approximately working at 210x.
On closer inspection, I could "derive" that the arms, particularly the
more well defined arm, using a UHC filter.. was actually reddish. This
more of a grey, but the mere subtraction of green from this area, does
give one the impression that with more light throughput, red would
be more clearly seen. Color was seen both with and w/o the UHC filter,
which mainly enhanced the outer regions of the nebula, nearly doubling
it's nebulosity.
In the bright center area, (rectangular) surrounding the Trapezium, that
is so often seen "burnt-in" to photographs, there were included
lacy threads of gas, and a nearly complete "canal" or dark lane cutting
all the way through it, (bisecting it , but offset)  opposite from M43,
opp. from
the dark wedge that pokes into it. This was not at all like any photos,
better resolution.
The outer arms were lacy, and delicate, very clearly seen, similar to
nearly colorless the further out you go.
The Trapezium stars, at the core of the brightest part of the nebula
 were a bit bloated, due to seeing . 4-5 stars were
clearly noted. More on the Trapezium stars (6) was reported on in a
observation report.
M43 looks like it is included in M42, a roundish piece cut off from the
 - Todd
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