Quote: Also, the "H-alpha test" was done for you by me (and others) using a variety of filter combinations to rule out a contrast effect. Red was seen in parts of M42 when a narrowband filter with H-alpha and OIII/H-Beta passband was used and was not seen when a filter that had only the OIII/H-Beta passband was used. Red was seen when an H-Beta line filter with a high red transmission secondary passband was used on M42 but not when an OIII filter *without* any red transmission was used. This is clear evidence that the red is not a contrast effect, as the red vanished when the filters without any red transmission were used. Why can't you understand this? Although it can be difficult to do, it is definitely *possible* to see reddish hues in M42, M8, IC 418, and Campbell's Hydrogen Star. It is your contention that it is not possible which is "dead".
The test must be made with a Ha alpha filter. It might be that the OIII with read leak passes the star field lights in a different way that without the leak (thus color constancy effects work differently). Given the examples that one can see red through a OIII filter without the red leak, who can say what happens in those critical condition.
You are so convinced that "every color must be real" that you prefer to question the colors of a photo (nor you point any other photo). But, let us suppose that the real red is really seen in some parts of M42 and IC418. Can we say that "every reported color is real" where there is the evidence that starting at 17-18 there are false color perception in *perfect* agreement with the experiments by Pokorny et al? How many real reds are there? I said I think zero, but if it turns out they are 2-4 is that very different?. If you clearly state that except for those few cases red is not seen then we will focus on those four candidates and see if they survive the Ha filter test. To see red, red must be not only above L-cones threhold (which happens in the hygenian region for example) but also *a lot lot lot* stronger than OIII to prevail on it.
As for what concerns the red in the outer fringe of NGC1353, I am afraid but the central part is brighter an richer of Ha (comapred to OIII which still is dominat). Thus there are two unbeatable points against your theory that someone very sensitivy to red might have perceived it:
1) in order to perceive red which is fainter than OIII one should have a sensitivity to Ha *greater* than *his owns sensitivity* to OIII. People sensitivity to Ha is 10% than that to OIII. You imagine somebody who has 200% sensitivity to Ha compared to *his own* OIII (a completely reversed perception of colors!)
2) If somebody would be really able to sense the red in the fringe he *should* also see the brightness and richer in red centre as red too. Not green.
There are serius experiments that fit very well the reports. Why not at least reading and evaluating them? Why ignoring them? How can one say they are not valid without even having read?
PS I google many NGC1535 oics: none shows any trace of red at all. Note that the following picture shows the centre less blue than the outer fring (in agreement withn the fact that the centre has *more* red than the fringe, so why the fringe is seen red and the centre green?).
Do you think that all the pictures are wrong? You probably will rebut the pictures (all?!?) because they do not represent the real perceived colors. The point is however that pictures are more sensitive to red than the eye.
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Re: Is it possible to see the nebula with colour?
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