Quote:Is a hydrogen beta worth the purchase? Does it make that big a difference?
Both the man of science and the man of action live always at the edge of mystery, surrounded by it. - J. Robert Oppenheimer
VISUAL -Orion XX12i -Orion 35mm Deep view, 26mm QC, 13mm Stratus -ES 9mm 100*
ASTROPHOTOGRAPHY -Nikon D700, too many lenses to count -Astrotrac -Atlas EQ-G
Quote:Although I think we're getting off topic... the original account was of color within IC434 (which personally, I've never seen any hint of).
David W. Knisely . . . . . . "If you aren't having fun in this hobby, you aren't doing it right." Hyde Memorial Observatory http://www.hydeobservatory.info Prairie Astronomy Club http://www.prairieastronomyclub.org
Quote:The $64 question is: Can the variation in color sensitivity among individuals amount to something of an order of magnitude, or a factor of ten? Specifically, can some enjoy a tenfold increase above the norm in red sensitivity? For that's about what it would take to permit red detection at all near to that claimed.
Quote:When different colors are present, the resulting color we see depends on the relative intensity. For any given image point, its color results from an admixture. The more dominant any particular wavelength, the more strongly the perceived color shifts to it. And so what red there is to be seen must 'fight' to get through the much more easily perceived blue-green.Photographically, the vast majority of emission nebulae are red dominant, but visually the red contributes essentially nothing. One does not find on offer visual H-alpha filters for a good reason; in only a tiny handful of all nebulae (including planetaries, of which Campbell's Hydrogen Star is a standout example) can any red be detected, and mostly with difficulty.The eye's poor red response, the visual dominance of other colors, the low surface brightness of most nebulae in the first place, and the light of the sky itself all conspire to make visual red detection in all but a few exceptionally bright examples impossible. Bias borne of familiarity with color images must to some extent be operating nowadays, else how to account for the lack of such reports in pre-color photography times, when even meter class and larger instruments were peered into? And knowing the numbers regarding the relative contributions of the light sources involved, and the human visual response, only reinforces this. It's so very easy to color the imagination with a combination of illusion and bias.The $64 question is: Can the variation in color sensitivity among individuals amount to something of an order of magnitude, or a factor of ten? Specifically, can some enjoy a tenfold increase above the norm in red sensitivity? For that's about what it would take to permit red detection at all near to that claimed.
A few thoughts:
- While informative, I think this thread is beyond the experience and reach a beginner. Any colors detected or perceived in nebulae are subtle at best.
- It is probably worth distinguishing between actually detecting a color and perceiving/seeing that color. The assumption here seems to be that perceiving/see red means that one was detecting a red color... I suggest that the fact that something appears red, particularly in the presence of other other colors, does not mean that it actually is red. The eye-brain is an amazing image processor but it is not fool proof.
A man is a small thing, and the night is very large and full of wonders.
Quote:I'm fully aware of the argument about the ability to perceive reddish hues in M42 as being due to visual contrast effects. What I don't understand is why the only times that I have been able to do so have been when large apertures were employed at very dark sites under exceptionally good conditions. I typically don't see any color at all in M42 from light-polluted locales, even when using a dome-enclosed 17" telescope.Dave Mitsky
Orion SkyView Pro 8" Equatorial Reflector Telescope
Orion Starblast6 Reflector Telescope
Celestron Eyepiece/Filter set
Sirius plossl 10mm,25mm,40mm
Orion Skyglow LP filter
Baader film solar filter (homemade)
Celestron 15x70 SkyMaster Binoculars
Every week I do something new to reduce light pollution. Eyes on the Sky is at 650,000+ views so far; more views = more awareness. Please consider sharing with others.
Scopes: 10" dob, 13" dob, 4" refractor
"Only gold is money, and nothing else. " - John Pierpont Morgan
Quote:There are two issues at play, with M42:1) lab studies show that when 2 gray squares, illuminated to *barely* the limit of scotopic vision, but one a tiny bit brighter than the other, are presented to the observer, we all see the fainter one as "reddish" or "pinkish" and the brighter one as "greenish". This alone says we should trust our eyes very little when used at or near the limits of vision, if color is seen.That we all see it is NOT a sign the color is there, merely that all of us have eyes that work the same way.2) when observing M42 (and heaven knows I've looked at this nebula with 2" to 60" aperture at least a thousand times over the years), sometimes more colors than simply greenish-gray or pinkish-gray present themselves.It seems that, on those nights, the nebula is SO bright in the telescope that a quick glance away from the scope shows that night vision has been damaged.And the range of colors seen extends to yellowish-beige, bluish, pinkish, purplish, reddish, mauves, and simple grays, and nearby NGC1977 appears quite blue. One such night, I drew a simple map of the nebula, indicating where I saw each color, and compared it to a color photograph of the nebula, and found I had correctly indicated where each shade was found. So I am certain that, under the right conditions, colors can be seen in the Orion nebula. My vision at the time was probably mesopic, and not purely scotopic.3) But these colors are not ALWAYS visible. As an experiment, I tried viewing the nebula through an H-alpha filter. Only the brighter sections could be seen, and the brightest part, even in H-a, was the central region.When using a filter that transmits H-b and O-III, the entire nebula can be seen. That's not surprising since every nebula that emits H-a also emits H-b at a lower level, and because our peak sensitivity at night hovers around 500nm (near the H-b wavelength).4) Recently, I've had a chance to compare narrowband filters that have substantial transmission at H-alpha with those that have zero transmission shorter than 700nm.It may very well be that the restriction of bandwidth creates a greater ability to see the reddish colors than a non-filtered view, because the non-filtered view didn't present them as strongly. Or that the diminishment in brightness of the entire field resulted in that red/green illusion at the limit. How to tell?It appears the reds I am used to seeing must be real, because they are visible in the filters WITH H-a transmission, but disappear with the filters that do not have H-a transmission.5) Different observers have different sensitivities to colors, but it seems that on the nights where I see many colors, or very strong colors, so does everyone else in the observing site, and with a wide variety of apertures. I did not record particulars about the observations, but a memory search recalls that these were nights of exceptional transparency (very low extinction) and darkness.So what can you say about the visibility of colors in M42/M43/NGC1977?--it varies from person to person--it varies from night to night--it varies according to the filter used--it varies by aperture (the reds were stronger in larger aperture)--if "at the limit", the colors may not be real.But if you have a night where you can see ANY tint to the fainter interior of the nebula, looks at those sections on either side of the central region and see if one side appears yellower than the other. If you see that, I believe you are seeing REAL colors in the nebula. Just don't expect to see them all the time.