Quote: I have used Hydrogen gas discharge tubes and spectrometers, so I can see what the H-alpha line looks like visually. Even when not using a spectrometer, I can see the gas discharge tube as a nice bright pink, which is very similar to (but quite a bit brighter) the shades of pink I see in M42.
This is contradictory in itself: you say that H-alpha at high intensity looks exactly the same color (hue and saturation) that when you supposdely see it at very faint level!! There is a huge amount of proofs that hue perception and saturation and chroma varies.
You simply do not read anything because you already know. I will no longer reply to you at least until you accept to read and discuss the points as is doing Don.
PS have you ever studied the sensor fusion processes that happen in the brain? Here there are lots of false color detection that happen at full illumination (figure at dim lights). But... you are sure that the dime faint pink is exactly 656 nm.... and therefore you se H-alpha.
http://www.purveslab.net/seeforyourself/ Look the effects of color dominants. why do they happen? because the brain, in attempt to evaluate the reflectance curve of an object has to subratct the spectrum of the incident light, which the brain evaluates with an algorthm that makes a long different processing path until high level object shape color recognition. BTW red is the color that happens when compensating a green dominant. A similar algorithm (google retinex) is used in automatic white balance in many camera. Look what happens throu a OIII filkter with NO red leak:
Surprise surprise you can see (and visually that happens) colors through the filter!! Not only: there is red, the black "K" is RED. I bet you would say that you saw the real red, in fact the letters are red... you see red, hence you see the real color... (well let us ignore the discrepancies in the K).
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