ETX-125 and M43

Well, practically no scientific images are true color, because the filters
being used....

I think my point was simply to make sure that the OP and others were aware that
the beautiful color photos they see, many from the hubble, some from amateurs,
are not accurate reproductions of what they human eye would see. In the case
of amateur photos, the colors are probably mapped rather accurately but with a
wider/different band width. With the Hubble, the color/wavelength mapping is
arbitray with IR and UV mapped into the visual spectrum.

jon

(SaberScorpX) wrote in message ...

The combined nebulousity of m42/43 is a naked-eye
object from even moderately light polluted skies.

I am skeptical about that statement, and my skepticism
has been bolstered recently by some reports from several
highly experienced observers who looked very carefully
for M42 under pristine skies and failed to see it
naked-eye.

I'm quite sure that what most people mistake for M42 is
the smeared out light of the various components of Theta1
and Theta2 Orionis, which are all just a little too close
together for normal eyes to resolve. Certainly, when I
look at the area in binoculars, it's the components of
Theta1 and Theta2 that reach out and grab my eyes. The
nebulosity isn't hard to see, but I can easily imagine
overlooking it, as Galileo did.

If people report seeing Theta1 distinct from Theta2, and
M42 clearly distinct from both of those, then I'll believe
that they've really seen M42. And I also believe people who
report seeing M42 as red. But the former feat would require
exceptional acuity, the latter would require exceptional
red sensitivity, and both (I believe) would require dark
skies.

Another way of looking at this is that if you can't see the
bright open cluster NGC 1981 one degree north of M42 naked-eye,
then you *certainly* can't see the nebulosity of M42 -- which
has to be considerably fainter than that cluster.

- Tony Flanders

The combined nebulousity of m42/43 is a naked-eye
object from even moderately light polluted skies.

I'm quite sure that what most people mistake for M42 is
the smeared out light of the various components of Theta1
and Theta2 Orionis

I have no problem discerning m42 from Theta1 and 2.
However, I have no problem ammending the statement to:

'Many see the combined nebulousity of m42/43 as a
naked-eye object from even moderately light polluted skies.'

The
nebulosity isn't hard to see, but I can easily imagine
overlooking it, as Galileo did.

We don't know that Galileo (and every other pre-telescopic
observer) simply overlooked it.
It's also possible that m42 hadn't brightened and expanded to
naked-eye visibility until many decades after it's discovery.
In fact, no recorded naked-eye observation was made until
1810 by Herschel.
(Not really caring to rehash an old debate.)

SSX

...some reports from several
highly experienced observers who looked very carefully
for M42 under pristine skies and failed to see it
naked-eye.
And I also believe people who
report seeing M42 as red.
But the former feat would require
exceptional acuity, the latter would require exceptional
red sensitivity.

Interesting. I've never considered it especially difficult to see
the separate fuzziness of m42 or occasionally seeing the
nebula tinted red thru a scope under the right conditions.

"Jon Isaacs" wrote in message
...
Well, practically no scientific images are true color, because the
filters
being used....

I think my point was simply to make sure that the OP and others were aware
that
the beautiful color photos they see, many from the hubble, some from
amateurs,
are not accurate reproductions of what they human eye would see. In the
case
of amateur photos, the colors are probably mapped rather accurately but
with a
wider/different band width. With the Hubble, the color/wavelength mapping
is
arbitray with IR and UV mapped into the visual spectrum.


OK, I misinterpreted your post. Sorry about that! And your point is a very
good one.

I'd like to mention that there is also the factors of (1) that at low light
levels it's been said that the faint light receptors in the eye often have
shades that look more like dark pale greens as interpreted by the brain, and
(2) that at brighter light levels due to the way the color receptors in the
eyes respond a lot of observers see pinks, apple greens, and faint blues on
hydrogen emission nebs. I've observed this, along with a host of others,
looking at M42 using a 60-inch Cassegrain.
--
Sincerely,
--- Dave
----------------------------------------------------------------------
It don't mean a thing
unless it has that certain "je ne sais quoi"
Duke Ellington
----------------------------------------------------------------------

(SaberScorpX) wrote in message ...

I have no problem discerning m42 from Theta1 and 2.

Wow! We're talking naked-eye, right? At 2' separation between
the closest components of Theta1 and Theta2, that is genuinely
extraordinary acuity. Can you separate the components of
Theta2 as well?

It's also possible that m42 hadn't brightened and expanded to
naked-eye visibility until many decades after it's discovery.

No, not really -- not without a drastic change in our understanding
of astrophysics. As someone who finds M42 not at all prominent in
small instruments, at low magnifications, and and in instruments
with a lot of scattered light, I find it *much* easier to assume
that it was simply overlooked. In fact, given the quality of
Galileo's scope, it would have been amazing if he *did* see it.

- Tony Flanders

Tony Flanders wrote:
(SaberScorpX) wrote in message ...


I have no problem discerning m42 from Theta1 and 2.

Wow! We're talking naked-eye, right? At 2' separation between
the closest components of Theta1 and Theta2, that is genuinely
extraordinary acuity. Can you separate the components of
Theta2 as well?

I can't split Theta1 & 2. But on a good night I can split eps Lyrae.

But I do find that the M42 patch is obviously non-stellar in the same
sort of way that M13 appears naked eye fuzzy. It is only the very
brightest square central bit that can possibly show up in urban lit skies.

And I have seen this from central Manchester, UK on the few very clear
nights in a sky that is rarely good to 5th magnitude. In decent dark
skies it is for me obviously diffuse around the star.

It's also possible that m42 hadn't brightened and expanded to
naked-eye visibility until many decades after it's discovery.

No, not really -- not without a drastic change in our understanding
of astrophysics. As someone who finds M42 not at all prominent in
small instruments, at low magnifications, and and in instruments
with a lot of scattered light, I find it *much* easier to assume
that it was simply overlooked. In fact, given the quality of
Galileo's scope, it would have been amazing if he *did* see it.

Are you by any chance partially red-green colour blind? The central
patch of M42 in a small scope seems pretty bright to me.

M1 and other very young SNR are pretty certain to have become dimmer
with time since Messier catalogued them. However, as you say regions
with active star formation and many bright high mass stars in them are
unlikely to have changed very much over a couple of hundred years.

Regards,
Martin Brown

I have no problem discerning m42 from Theta1 and 2.

Wow! We're talking naked-eye, right? At 2' separation between
the closest components of Theta1 and Theta2, that is genuinely
extraordinary acuity.

No. No bionics.
Just saying that I, and many I have observed with,
have little trouble distinguishing the fuzziness of m42
from the glow of Theta1-2 under good conditions.

It's also possible that m42 hadn't brightened and expanded to
naked-eye visibility until many decades after it's discovery.

I find it *much* easier to assume
that it was simply overlooked. In fact, given the quality of
Galileo's scope, it would have been amazing if he *did* see it.

Given their skies, I find it amazing that anyone missed the
obviously naked-eye oddity/nebulousity of m42 at it's current
size and brightness. Especially gifted and obsessed observers
like Brahe and Bayer.
Herschel for one, by comparing his and others' previous observations
and size estimates, was convinced it had dramatically brightened
and expanded over the prior 170 years.
Makes for a good debate anyway.

Hey, did the OP find m43 yet?

Martin Brown wrote in message ...

Are you by any chance partially red-green colour blind? The central
patch of M42 in a small scope seems pretty bright to me.

No, my color vision is perfectly normal, as far as I know.

The central part of M42 seems quite bright to me in a small
scope at high magnification. But that central area is truly
tiny, probably no more than 4' across, and at low magnification,
as in 7X or 10X binoculars, it just looks like a haze around
the brilliant Trapezium stars, much as though the optics were
fogged up.

- Tony Flanders