Telescope Reviews: Re: Is it possible to see the nebula with colour?

I also found those pics yesterday late night (here in Italy).

I took the OIII and Ha pics and combined them respectively in R and G channels and the result is the color picture also shown in the site. Then I did the following check: I reduced the lightness of the Ha image until only the huygenian region and arches remained (what is reported to be seen in the Ha filter). This is to reproduce (somewhat) the reduced sensitivity to Ha (which is 10% wrt to OIII). In other words I got a new Ha image showing grossly what is reportd by Nils and Don... (but let us wait after the nex week end).
Then I combined the two pics together, to get a "natural" color image (see many of the links already posted about "natural" color images. I will post the results in my blog. What happens is that the image is overall geenish, with the huygenian region gray (geer+red makes gray).
I see gray the huygenian region (or at least pale green). But I recall that I saw that region red with a W23A filter (and also Nil reports seeing that region red in Ha filter). Thus it is possible that I see that region gray because i see both OIII and Ha and my personal sensistivity to OIII and Ha are such that they form gray. If I were less sensitive to red I would see green. In other words the greener one sees the huygenian region the lesser he is sensitive to Ha. This explains to me clearly why I do not see that much green in the huygenian region despite it is in the mesopic range: I do in fact see a lot of red too and that is whay the resulting color is gray form me.

Surprise surprise. If that exlanation is correct people who see gray the huygenian region are actually those we see better the real red!!

The fainter regions are not colored for me (not that much). I see the arches pale red and since they are grey and given the fact that I do see real Ha in the huygenian region I suspect that the reddish is a contrast effect.
The regions that are more reddish are M43 and the filament. But that happens only when OIII and Ha are combined with the same wheight. If Ha is wheighted according to eye sensitivity those regions are not red. Anyway those two are the best candidates for real red vision.
I will carefully look at the M43 and the filament. If I cannot see them in Ha and they look reddish (they are fainter than the arches) I will know that the most red part of M42 is not enough red and bright to be seen as real red.

So... the point is: there are maybe two parts in M42 at the edge of red vision. M27 was undobutley seen with inverted colors (the contrast effect described in papers, I see the same effect on the arches, and the same effect is going to be a lot stronger for people whe see greener the huygenian region) and that is still a relatively brigh nebula. What about reports in fanit parts of other nebualsa or, for example, in the Veil?

Edited by Mauro Da Lio (12/04/07 03:28 AM)

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