where is the red stuff?

I don't know, this was about 15 years ago or so, and it wasn't very
prominent, just a sort of pinkish overlay over the much stronger green.
Perhaps it was an illusion of contrast (red being the compliment of
green), but I had seen it on several occasions. At my current age I
doubt I would see it now, at least not thru a 10 incher.

"urban astronomer" wrote in message
oups.com...
I don't know, this was about 15 years ago or so, and it wasn't very
prominent, just a sort of pinkish overlay over the much stronger green.
Perhaps it was an illusion of contrast (red being the compliment of
green), but I had seen it on several occasions. At my current age I
doubt I would see it now, at least not thru a 10 incher.
My own experience of seeing colour, was largely some years ago. I strongly
suspect that my eyes now, do not give quite the same sensitivity, and the
irises, don't open so far. The commonest colour was green, and this was
visible in several objects, which makes sense, given the relative
sensitivity of the eye. I did feel that I saw some other colours in Orion
though. A few 'wisps', of a pinky red, and some slightly yellowy brown
hints. However just like all colours this faint, these were 'hints',
rather than a strong colour. These were from what was then a dark site in
north Essex (now unfortunately badly light polluted), in good seeing, and
with very well dark adapted eyes. At the time I can remember having
'contests', with myself, regarding how many stars I could see in the
Pleiades, and reckoning that it was about fifteen.

Best Wishes

"Chris L Peterson" wrote in message
...
On Tue, 24 Jan 2006 08:48:22 +0000, Martin Brown
wrote:


We sometimes see green in the Orion nebula because it is so bright, even
though it isn't primarily an OIII source. Under dark skies, I even see
the green color when viewing the nebula unassisted. I've never seen red
in a telescope of any size, however.

The red isn't at all as it appears in a photograph, but there is definitely
a visible pink hue to the dark line between the area surrounding the
Trapezium, and the three bright stars to the west(?) of the core.

I first saw this in a 12.5" Dob, and then a 16" Dob. Interestingly enough,
it is not visible directly, but with averted vision (of a kind). I know that
doesn't seem to make sense as we understand averted vision to be a
stimulator of the contrast sensitive b&w sensors in the eye, but hear me
out.

I'm thinking it's possible that the brightness of the Trapezium core is
enough to stimulate the eye, such that when you are looking directly at the
Trap, the outer edge of the main core of the nebula falls within the field
of view of the main color receptors in the eye. If you look away from the
Trap area (even slightly), the light falls off enough that the color
receptors are deactivated. So, it is only when you look directly at the
Trap, that you can detect the pink hue at the averted position. Of course,
this color activation also allows you to see the central glow as a pastel
green.

On Tue, 24 Jan 2006 13:19:43 -0500, "Stephen Paul"
wrote:

The red isn't at all as it appears in a photograph, but there is definitely
a visible pink hue to the dark line between the area surrounding the
Trapezium, and the three bright stars to the west(?) of the core.

The interesting thing about color in M42, and around the Trapezium
specifically, is that there is so much reflected light. The Trapezium
region doesn't even show much red in images, because it is flooded with
white from nearby stars. Images of the larger nebula generally show a
very unsaturated red compared with most Ha regions, again because there
is so much reflected light.

It makes me wonder if the appearance of red in M42 has more to do with
an illusion caused by contrast effects (a white core surrounded by
green) than it does with actually seeing Ha emissions. The eye is really
insensitive at 656nm- rods are about 1000 times less sensitive than they
are at 500nm, and cones are about 20 times less sensitive than they are
at 550nm.

In general, I remain skeptical whether any DSOs are sufficiently bright
in Ha to stimulate color vision. I don't doubt that some people see red,
I'm just not convinced they are seeing Ha emissions as opposed to some
sort of visual illusion.


I first saw this in a 12.5" Dob, and then a 16" Dob. Interestingly enough,
it is not visible directly, but with averted vision (of a kind). I know that
doesn't seem to make sense as we understand averted vision to be a
stimulator of the contrast sensitive b&w sensors in the eye, but hear me
out.

When you use averted vision, a question arises as to how your brain
interprets color. Now most of the signal is coming from rods, and the
cones that are present have different densities depending on class, with
blue being the lowest.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peerson wrote:

In general, I remain skeptical whether any DSOs are sufficiently bright
in Ha to stimulate color vision. I don't doubt that some people see red,
I'm just not convinced they are seeing Ha emissions as opposed to some
sort of visual illusion.

Well, if you don't have any red sensitivity in low light levels with
your eyes, you obviously won't see any red in DSO's, but to generalize
that experience to others may be inaccurate and perhaps a little unfair.
There are a number of Deep-Sky objects which will show reddish color
in moderate to large apertures, but the effect is generally fairly mild.
The one which comes to mind as the most vivid is the planetary nebula
IC 418, "The Pink Planetary", as it has a rather rosy-looking outer
shell. I have seen this reddish shell in my 10 inch, although seeing
that red color is considerably easier in a larger apertures. The
reddish hues in parts of M42 are fairly well known, but tend to be
somewhat elusive. I had an older Lumicon OIII filter that had a huge
"red leak" secondary passband, and with the rest of the nebula toned
down, it showed considerable faint red coloration in some parts of M42
and M8. My H-Beta filter has a considerable red passband, so much of
M42 tends to look reddish, although some of this isn't H-alpha but
rather scattered continuum that has merely been filtered by the red
secondary passband. Another little red wonder is the tiny planetary
Campbell's Hydrogen Star, which looks a little like a faint carbon star
in moderate to large apertures. Red coloration is not often seen (and
when it is seen, it is usually quite marginal), but it is definitely
possible for the human eye to pick it up under certain conditions.
Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 13th Annual NEBRASKA STAR PARTY *
* July 23-28, 2006, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

On Tue, 24 Jan 2006 16:08:43 -0600, David Knisely
wrote:

Well, if you don't have any red sensitivity in low light levels with
your eyes, you obviously won't see any red in DSO's, but to generalize
that experience to others may be inaccurate and perhaps a little unfair...

How so? I'm certainly not saying that some people don't see red in some
DSOs, I'm only saying I'm skeptical that the red is associated with Ha
emission. We are talking about something at the threshold of perception,
and which only a minority of people seem to see. Odd visual effects are
very much a possibility.

"Skeptical" doesn't mean I consider it impossible that people are
actually seeing Ha emissions, it just means I'm, well, skeptical g.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peterson wrote:

How so? I'm certainly not saying that some people don't see red in some
DSOs, I'm only saying I'm skeptical that the red is associated with Ha
emission. We are talking about something at the threshold of perception,
and which only a minority of people seem to see. Odd visual effects are
very much a possibility.

"Skeptical" doesn't mean I consider it impossible that people are
actually seeing Ha emissions, it just means I'm, well, skeptical g.

OK, I kind of misread what you were saying. Still, in the cases I
cited, the red is mainly due to H-alpha emission. Campbell's Hydrogen
Star is notable in that the only filter that seems to work well with it
is the H-Beta filter (one of the few that do work with the H-Beta).
However, with just higher power, the reddish hue of the H-alpha emission
is quite noticable, as is the red H-alpha emission from the outer edge
of IC 418. M8 also looked somewhat red to me in an older Lumicon OIII
filter that had an odd "red leak" passband that allowed H-alpha to get
through almost undimmed. In the case of M42, it is a bit different, as
the core region looks a pale greenish-blue without a filter but a
definite bright bluish-green with the Lumicon UHC filter. I don't see
much in the way of red in M42 with my 10 inch Newtonian unless I use
that old Lumicon OIII filter with that red secondary passband or the
Lumicon H-Beta which also has a red passband (although not as well
placed for H-alpha as my older OIII has). Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 13th Annual NEBRASKA STAR PARTY *
* July 23-28, 2006, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

well I can see red in my C8 and Meade Mak. Whatdoes that tell ya?
The same in my Cave 8" newt,

David Knisely wrote:

Well, I'm afraid that you will see very little red coloration in M42.
The human eye is very insensitive to red light at the low light levels
present in many deep-sky objects, so the brilliant reds you see in
photographs are usually not visible. In some fairly large apertures
(usually above 10 inches) some very faint hints of reddish coloration
may be seen in M42, but they are pastels. The best powers to use on M42
are those between about 40x and 150x, as they allow you to see much of
the fainter outer detail (especially with narrow-band nebula filters).
The most color you will usually see in nebulae is a sort of bluish-green
hue in the brighter parts, as most of the outer sections will be fairly
colorless. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 13th Annual NEBRASKA STAR PARTY *
* July 23-28, 2006, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

Wait for a crisp clear night. You'll see it. This isnt rocket "appliance"!
I see red via my C8, Meade Mak, 8" newt.... all the time. But my eyes are
the best available (and I have land in Nebraska for sale!). Just keep
lookin.
You'll see it. Look against the larger white and bluish background. If you
pick
up some green the red is there.
Good luck...



pascal wrote:

I am new in Astronomy. I have recently purchased a newton 8" telescope
and have spotted some of the Messier objects and yesterday night for
example got to see M42 with a magnification of 200x. I saw everything
that is in the usual photos except the red color that we usually see in
pictures even of amateurs.

Can someone tell me what's type of telescope you need to see the red
color that makes a real plus.

Thanks