Well, Mauro's logic is inescapable given the premises. The response of the eye under low light conditions is, indeed, what is explained in the articles. There is a counter-argument, though, and it is a strong one: In large scopes (I've had the privilege of looking at many nebulae in 28-32" scopes), the colors that appear as the nebulae appear larger and brighter, are reds and shades of red. The Orion Nebula appears gray with no color in small apertures. In larger apertures, the central area appears greenish. In still larger apertures, the fainter areas appear shades of pale rose and peach and the "arches"(or "wings") section now has a greenish tone like the central area. All of those comments are consistent with the vision experiments and conclusions about false color. But, with still larger apertures, the "arches" become reddish and have streaks of deep red color in them, and the very faintest parts of the "diamond ring" (the opposite side of the nebula where the arches come together to form a large ring shape) appear greenish. The brightest parts of the nebula (except the central area) now appear reddish and the fainter sections appear greenish-gray. Could this be a contrast effect? Possibly. However, I've noticed that, after staring at the nebula for a while in a 28-32" scope, my night vision is ruined and it takes quite a while for perception of really faint objects to return. The nebula is bright enough to damage my night vision! I strongly suspect that my vision at that point is mesopic, and that the color perception has strengthened because I am, indeed, seeing "real" and not "perceived" colors.
Another problem I have with the assumptions in the articles is color perception in objects. I see faint pinks in M20, M8, M17, which is consistant. But I see faint blues and greens with no reds in most planetary nebulae. Now perhaps they are bright enough in surface brightness to activate the brighter perception which would shown greens. But all of these nebulae display outer shells and details which should show red because they are much fainter. But they don't.
Another problem is that several individuals, when looking through the same scope on the same night at the same object do not all perceive color in the same way, in the same amount, or even at all. This implies a greater range of variation than the conclusions of the articles referred to.
So what is the truth? High visual sensitivity occurs in some individuals. Some individuals perceive colors better and at lower levels of illumination. Some individuals see much better in the dark. That most do not does not prove that no one does. Lab tests form conclusions about the subjects tested. Tetrachromaticism exists in some women--imagine the "skew" of a lab test with such an individual as part of the "N". The only way to form a valid conclusion about vision is to have a large test group. How large is required to form conclusions applicable to general humanity? I don't know.
But I suspect that one of the things that may lead people to astronomy in the first place is an improved ability to see in low levels of illumination. It would be interesting to test a group of experienced astronomers and compare the findings with the general population. Now that would be illuminating! (sorry for the pun).
The premise that all humans see things the same is where, I think, the most valid criticism lies. I participated in a test of hearing several years ago in which hearing sensitivity and range were tested in over 400 individuals. The assumptions about hearing, especially in frequency range, proved to only be an approximation with huge deviations above and below the "norm". 20KHz is often cited as the highest frequency of human hearing. In our test, the range was 12KHz to over 23KHz. I suspect the range in vision is equally as broad. David cited the individual whose vision extended into the near infrared. Such individuals have problems maintaining night vision even when red monochromatic light is used. Some individuals simply see better in the dark. Others always need some illumination to see.[I remember someone who was amazed that I could look up the chart number in my Uranometria atlas with only the light from the sky--he couldn't see the black ink on the page and could barely make out the outline of the book. We were both amazed at each other's vision. ]
Still, Mauro's logic is inescapable. I suspect the truth lies somewhere between the conclusions of the researchers and the experience of astronomers. But how to set up a test........
-------------------- Don Pensack
12.5" Truss Dob, 5" Maksutov
Sustaining Lifetime IDA member, TeleVue junkie
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