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I don't have to explain the photo! It does *not* represent the situation where you are viewing a nebula with a filter. End of story.

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The photo shows that the leaking of light (not monochromatic light) may induce the algorithm for white compensation, and likewise the brain (it happes the same), to produce colors from nothing.
A filter with the red leak just do that: lets some red light from stars to leak into the field of view. I do not know if this might be an explanation, however I think that the red-leaking filter test might fail and should be regarded with care and replaced as soon as possible by a Ha test.

As for what concerns the views with different filters, the point is that if real red exists in one spot, it must be seen with both methods. I understand that red was seen in spots far away from the huygenian region with the red-leaking filters, the same spots were not visible at all in the red filter (red seen in the huygenian region and somewhat away it). Am I wrong?
If this is the case (a spot seen red with red-leaking filter but not seen with the red filter), it would be another proof (besides M27 and NGC1535) that at least those spot colors were not real. How is it possible to see red patches that disappears in a red filter?

The countrary is of course instead possible: it is possible to see red the huygenian region when a filter "isolates" the red components, yet that region being richer of OIII appears green.

To see red one must meet two conditions:
a) find a patch that emits Ha sufficient to stimulates L-cones. This is possible and a Ha or red filter will show all the candidates patches and they will be red (being detected by L-cones).
b) the same patch must emit very little or no OIII (otherwise OIII wins and that region is gray or even green depending on the amount of OIII). "Very little" is necessary because the sensitivity to OIII is a lot greater than that to Ha.

Conditon b is indeed the most difficult to meet. My plans are to identify the candidate patches with Ha filter... hopefully as soon as the whether permits.

Edited by Mauro Da Lio (12/14/07 02:11 PM)

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