I found a picture of the central region of M42 (the so-called Huygenian region). This area is more or less the area that is visible even with the red filter .
If there is a chance to actually see the colors this is the area where to look. In particular, the challenge is to capture the color of the point marked C in the link.
The photo of the central region of M42 is this.
This picture shows two areas where the prevailing issue of Halfa, which are: a right trapezius, the other a linear structure at the lower boundary of the brightest part.
must be said immediately that this picture combines emissions Halfa (red) and OIII (blue-green) pesandole about the same way. In fact, if we separate the three channels we see that the intensity of R, G, B respectively is this:
In fact the human eye is about 10 times less sensitive than Halfa allOIII. In fact, when you look at the nebula Halfa in the image seen through the red filter is much weaker. Something like this:
In fact with the red filter you see more. But OIII images are very much more intense (in fact you can see the entire nebula and not only in the central part OII). Grossmodo il rapporto di intensità fra il rosso e il verde dovrebbe essere rispettato con la figura modifica sopra (o al più è a favore del rosso visto che nel verde la nebulosa è abbagliante).
Se combiniamo il rosso così definito, con il verde e blu iniziali otteniamo una immagine che riproduce realisticamente i colori di M42, pesando l'emissione Halfa molto meno di quella OIII in accordo con il fatto che l'occhio è sensibile in maniera diversa alle dioverse lunghezze d'onda.
Il risultato è questo. Le due aree nelle quali l'Halfa è più intenso sono di colore verde con un po' di rosso. Cioè meno verdi, biancastre. ua va indirizzata la nostra attenzione.
E 'can see these areas pink or red? The answer to this question is simple: look at them in Halfa, then look at them in OIII. In which of the two filters are more intense? There is no doubt that much will OIII arrangements. So there's lots of green and little red and objectively can not hang on the side of red, will be at the "less green or white.
However, you may find that the dominant green of the nebula (the phenomenon of color compensation, also explained by Gasparri) we do not see green as green as rosy. The fact remains that we can easily ascertain that the OIII filter those areas that are brighter with the filter Halfa. For example also in this picture the linear structure appears reddish, but try to measure the RGB values \u200b\u200band find that it is only "less green."
I observed several times carefully the linear structure at the bottom of the picture and, in fact, has a green a little 'more conducive to white (if desired you can see the pink, but I would say that white is right in line with the relative intensity of Halaf and OIII).
I have never seen the second (and harder) area next to the harness (because I realized that only with this development there is also that possibility).
This is any trace of red (pale green) that you can see in the most brilliant nebuolsa brighter than the sky.
PS Halfa in the absence of a filter, you can use a red filter type W25 or W29. These are passed about 98% of red light and cut almost all the green.
PPS could also try a yellow or orange filter, which should depress the green to a level closer to red. In this way, although weaker, the image of the nebula should have the colors balanced.
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