"Mark De Smet" wrote in message
...

I recently got an orion XT10 IS, and although I have not had a chance to
get to a dark site, I did have a chance to take a peek at the orion
nebula from my porch.

From my highly light polluted porch (chicago suburbs), the nebula
appears very clearly green.

In my experience:
In an 8" SCT, the central glow of M42 appears grey.
In a 10" F5 Newtonian, the central glow appears grey, with a hint of very
pale green
In a 12.5" F4.8 Newtonian, the central glow appears grey, with a hint of
very pale aqua.
In a 16" F4.5 Newtonian, the central glow appears pale aqua and the area
along the edge appears ever so slightly tinted toward red (looks sorta
pink).

I don't think that it ever appears "green", although I once made that claim.
Supported by the results above, over time I've come to the conclusion that
with the increased brightness of increasing apertures the response of the
eye is most sensitive first in green, then blue and then red. I have no idea
if that tracks with what other science indicates about the response of the
human eye.

A second piece of empirical data would be that when surrounded by red light,
the eye has less trouble reverting back to its former state of dark
adaptation than it does under blue and green respectively (green being the
worst of the three, and second only to white).

Stephen Paul (as always, willing to be wrong)