I know the official position is to consider that human eye does not see the red color at night.
Unfortunately, or rather fortunately for me, as soon as I have a look at an emission nebula, this one becomes pink, then red, if:
- the nebula is sufficiently bright,
- I watch through the eyepiece for a long time, sometimes half an hour,
- and of course, with a filter which let pass the H aplha.
I'm sure, some of you won't believe me, but what can I do ? Here are two recent examples.
First, the Rosette nebula, through my 25" dobson, with the new filter Duo Narrowband, from Clycops Optics. I saw it in pink, because I was in a hurry. The nebula was much after the transit, and was falling down towards the horizon. So, I didn't stay a long time at the eyepiece, but I'm sure the pink would become more pregnant if I had spent more time at the eyepiece.
Secondly, Barnard's Loop, through a 4" refractor, at weak power. The filter I used is a Lumicon UHC fromm de last century, which let pass all the red.
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