Author Topic: nebula/ color  (Read 925 times)

caheadhilldea

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Re: nebula/ color
« Reply #15 on: January 16, 2018, 11:01:29 PM »
Cannot recall seeing any color but equally never actually looked for it either. May have been there.
General reading of reports seems to be that for M42 you need 14", maybe 12" in suitable conditions. They seem the most common instances.
Have read one maybe two who said color observed with an 8" but if so it is, or seems, rare, very rare.

Devon Dank

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Re: nebula/ color
« Reply #16 on: January 18, 2018, 01:00:04 AM »
Gunny, at our age the chances of seeing red/pink are slim and none. Had you a set of young eyes, you would see gray, green, bluish undertones and a hint of red or pink here and there in M42. I know of no other object in this hemisphere that will offer any other colors other than grey or green in DSO's. Should you ever be fortunate enough to go to Chile and visit the observatories there, you might indeed see a hint of pink or red in the Carina Nebula, a monster that dwarfs M42. But hey, you're retired now. Maybe you'll do it one of these years...

Semper Fi
STARKID2U

Eric Shaffer

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Re: nebula/ color
« Reply #17 on: January 23, 2018, 02:31:24 AM »
Nope, I've never seen any nebula colors. They all look gray to me.

Zack Tucker

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Re: nebula/ color
« Reply #18 on: January 23, 2018, 04:23:27 PM »
I have looked a number of times for color in M42/43 with the 16" premium Dob, Naglers, Ethos and Orthos without ever having seen any at all except that gray/green commonly on view. Incredible detail, amazing extension and Trapezium alphabet stars through G but never any color.
Late summer and into fall this year i used the visibility of M57's CS to predict the night's conditions. Held steadily via averted half the time at 600x and steadily >50% of the time in direct at 839x, I expected good conditions. Less than those results meant less beneficial conditions. But I've never seen color in the nebular ring. And I've looked hard for it.
But NGC7009, NGC6905, NGC6543, NGC6818, NGC7662, NGC2392, NGC3242, and NGC6210 which are all bright planetary nebulae have all appeared with color. Mostly blue, green or blue-green.
Nebulae in which I have failed to see color though I have tried include N2022, M20, IC418, N2359, N2371/2, N2438, N4361, N6309, N6826, any number of prominent emission nebulae and likely more I forgot and cannot find notes on.
My 67 year old eyes may explain some of the failures to see color even in objects whose names imply color like IC418, the Raspberry Nebula. Others have seen it in objects I have not.
But I will not be terribly surprised to hear some day that an observer has seen a red Rosette Nebula w/o filters in a 6" mass-market Dob. I won't believe it but I won't be surprised to hear it.
Astrophotographs can inform our observations constructively and they can mislead our expectations.

sdelbapaglo

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Re: nebula/ color
« Reply #19 on: January 25, 2018, 05:00:14 PM »
Firstly, let me say that I concur with Tony's post upstream about the colors he sees. I've only detected color in a handful of objects and for most of them the colors were quite subtle, even with my 20" under Bortle class 1-2 skies. Planetaries can be the exception, however, with their bluish and greenish coloration being quite distinct even with relative small scopes.

I would also like to point out several other situations that newer hobbyists may not be fully aware of, some of which can influence what you think you are seeing. The first of these is that the colors seen in both amateur and pro images have usually been greatly enhanced through lengthy processing until the colors are often rendered incredibly over done. Such intense color simply do not exist in these objects when viewed by the human eye, even were one to have use of a telescope 10x larger than the largest in existence today at their disposal.

Subjective colors can be imagined if the observer goes to the eyepiece too familiar with those color images of the particular object that he's seen on line or in the magazines. This can even be true if he's simply read here too often that such and such a color is commonly reported on by folks on CN. The human mind is easily influenced and prior knowledge of something can create the illusion of something being there that truly is not.

Then there is also the problem of complimentary colors, those that can created mentally in areas adjacent to stronger colors. Thus, a green shade in a nebula may cause the illusion of a seemingly reddish hue in an area nearby which is really white if viewed in isolation. This is extremely common in regard to double stars, where the primary is say orange and its truly white but fainter companion seems distinctly bluish, or greenish.

BrooksObs

Justin Prasad

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Re: nebula/ color
« Reply #20 on: January 25, 2018, 08:10:52 PM »
Some good stuff. My experience:

- Large exit pupils mean brighter images, a better chance of seeing color. That means lower magnifications.

- Larger scopes allow both large exit pupils and higher magnifications, useful in seeing color.

- Planetary nebulae can be very bright and show color. NGC-6572 is magnitude 8.0 and about 12 arc-seconds in diameter. It's surface brightness is about 13.2 mpsas. At low magnifications, it appears as a green star, maybe slightly fuzzy. By comparison, the Eskimo Nebula is magnitude 8.6 and about 3 times larger in diameter, that means it's surface brightness, it's intensity, is 15.7 mpsas, or about 1/10th a bright. Any planetary with blue in it's name will likely show some color.. The Blue Flash, the Blue Snowball, the Blue Racketball, which happens to be NGC-6572.

- Brooks Observatory(among others) makes some excellent points. The familiarity with published images can affect what one sees. Any DSO colors other than bright planetary nebulae will be subtle.. I rarely look at images of the DSOs I am observing and if I do, they're generally viewed through a red screen so I am hopefully not using averted imagination.

As Brooks says, complimentary color perception is also an issue, is what I am seeing real of just an artifact of the way the eye sees and the brain processes that image. When viewing M42 in a relatively large aperture scope, I often see the area around the trapezium as neon green and parts of the wings as sort of a dim rust red. But, as real as they seem, they may well just be artifacts.

Even with a large scope like the 22 inch, I am not expecting to see color, the rods see in gray scale so the dark adapted eye has a hard time seeing color.

Jon

ermaudyvi

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Re: nebula/ color
« Reply #21 on: January 30, 2018, 08:28:12 AM »
Being deeply dark adapted can actually be disadvantageous for discerning color. Any object having sufficient surface brightness to elicit a response from the retinal cones (color receptors) will do so with slight or even no real dark adaption having been undergone. Indeed, some folks have exposed their eyes to pretty bright white light at intervals to ensure little dark adaption occurs while observing colorful objects.

From my own experience, at dark sites and as the night progresses my color response becomes worse, with the colors getting ever subtler compared to their more obvious intensity earlier in the evening. After a spell in the observatory warm room under fairly bright incandescent light reading maps/charts or engaged in chin wagging  , upon stepping back outside the color intensity of sky objects is refreshingly boosted.

If an object has surface brightness some 2 magnitudes, or 6 times brighter than the sky, its color will not be much 'washed out' by the color of the sky; the object color will sufficiently dominate. For objects having SB of 18 MPSAS, which is near the color detection threshold, the sky should therefore be no brighter than 20 MPSAS. A blazingly bright nebula of 14 MPSAS will have its color seen through terrible sky glow of 16 MPSAS. Now, the sky color itself, if bright enough to be discerned and not so much different to the object color, will offer little color contrast and therefore likely make the object as appearing 'colorless.' But nonetheless the retinal color response is in operation.

As to astro images, and particularly of nebulae. Many folk describe them as having the color greatly 'exaggerated' or 'intensified.' Not necessarily. Emission nebulae shine at very discrete wavelengths of line emission, which colors are as pure as can be found. Where a particular color of emission greatly dominates, it will record as quite intense.

A final point, to augment BrooksObs' comments. Prior familiarity with an object's photographic aspect is a potentially deadly source of bias. And combined with the well-known red-green color illusion, can make for spurious detection of reds where green is seen. Just be aware of these sources of potential false detection.

Troy Clayton

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Re: nebula/ color
« Reply #22 on: January 31, 2018, 01:06:41 AM »
I would argue that perhaps the best and happiest way to observe color in astronomy is to expect none. Then when you do notice color it is probably real and quite exciting.

Drew Bullets

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Re: nebula/ color
« Reply #23 on: January 31, 2018, 01:36:16 AM »
Quote

Many astro images, particularly the Hubble images are pseudo colors, the colors are assigned to wave lengths far from the visual spectrum. Even if pseudo colors are not used, cameras can capture a much broader spectrum than the human eye so the colors can be captured at wave lengths that are invisible to the eye.

Jon

Jim Parker

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Re: nebula/ color
« Reply #24 on: January 31, 2018, 05:59:28 AM »
Indeed, Jon. Such color schemes as employed like the 'Hubble palette' can and will have even fairly similar-color, adjacent mission line wavelengths assigned rather different color in the interest of highlighting their contribution in both intensity and location. This is certainly misleading visually, but most useful astrophysically.

Nicholas Becker

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Re: nebula/ color
« Reply #25 on: January 31, 2018, 11:44:21 AM »
Quote
Quote

The Orion Nebula is incredibly colorful imo with a 12 inch scope. Ive seen all sorts of color in the Orion Nebula. I’ve also green and orange in the ring nebula, with a 12 inch scope.

Your color vision must be much more sensitive than most people's.

I have never seen colors in the Ring, though I do see many of the more intense planetary nebulae as strikingly bluish or greenish. NGC 2392, the Eskimo, in Gemini, is a good example.

As for the Orion Nebula, I see a subtle but pretty obvious pastel green in modest-sized scopes. In big scopes, the Huygenian region has reddish veins. Very striking, though still quite subtle.

I've never seen color in any other emission nebula.
M42 under dark skies is very colorful in my 12.5" Cave, the first time I viewed M42 it was absolutely stunning with greens and reds being very obvious. Before my 12.5" scope I had a 6" Cave and I don't remember ever seeing much color but my Meade 8" shows quite a bit of color. It may be that my eyes have better color perception than others as my daughter seems to see less color than I do even though her young eyes are more sensitive than mine when looking for faint objects.

Tim Jauregui

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Re: nebula/ color
« Reply #26 on: February 02, 2018, 03:32:59 PM »
Hummmmm...I tend to see color in everything in my old eyes. Dark skiesJack

linghetade

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Re: nebula/ color
« Reply #27 on: February 09, 2018, 01:29:48 AM »
Quote
<p class="citation">QuoteAs to astro images, and particularly of nebulae. Many folk describe them as having the color greatly 'exaggerated' or 'intensified.' Not necessarily. Emission nebulae shine at very discrete wavelengths of line emission, which colors are as pure as can be found. Where a particular color of emission greatly dominates, it will record as quite intense.


Many astro images, particularly the Hubble images are pseudo colors, the colors are assigned to wave lengths far from the visual spectrum. Even if pseudo colors are not used, cameras can capture a much broader spectrum than the human eye so the colors can be captured at wave lengths that are invisible to the eye.

Jon[/quote]
Indeed. They edited the hubble site and removed the part about the images being made, not taken.
The truth can be so disappointing.
But regardless, there are viewable phenominuminums that are way beyond Amebic human explanations, and those are what fascinate me.
No matter what color they appear to be.

Mohamed Wiest

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Re: nebula/ color
« Reply #28 on: February 09, 2018, 10:28:47 AM »
I've been able to detect somewhat vivid colors in M42 from very dark sites under exceptional conditions and with apertures of 14.5 inches and larger. From mediocre sites like the orange-zone ASH Naylor Observatory, I see very little color, just a pale greenish-white, within M42 using a 17" classical Cassegrain housed in a dome.

I've also seen the characteristic ruddy (if that's the right word) colors of IC 418 and Campbell's Hydrogen Star. M57 has never been more than a very pale blue for me. On a few occasions, I've detected color in M27 (John Vogt's 32" ATM Dob at Cherry Springs State Park) and a faint pink once in NGC 6960 (John Vogt's 32" ATM Dob at Stellafane). One of the most colorful nebulae (other than bright blue, aquamarine or green planetary nebulae such as NGC 3242, NGC 6572, and NGC 7662) that I've ever witnessed was the bright orange Homunculus Nebula (22" Starmaster Dob from Lake Titicaca in Bolivia).

There's a list of DSOs that display color to one degree or another athttps://www.cloudyni...hat-have-color/

Dave Mitsky