It can appear greenish. Part of this is the human eye response. If enough
photons hit the eye to activate the color receptors, the eye is tuned to see
greens better than reds. Also, I've heard where many people perceive some
shades of grey as greenish, but this is hearsay.

Remember that if hydrogen is the predominant light emitter, and if it is
excited enough, you will get the three visible wavelength color lines being
produced; red, green, and blue. Due to the way the eye responds to colors
when the lighting is bright enough, your eye will favor seeing greenish
shades. I've also seen this effect in a lot of diffuse nebula images with
my single-shot color camera, whose CCD has a spectral response that mimics
the eye's.

Through a 60-inch Cassegrain, I've seen shade of just about every color in
the Orion nebula except perhaps purple, but even there the colors were not
bold, but shades of colors, more like pastels.

--- Dave

"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. Having only seen it before in lower quality and
much smaller apperature scopes, it always appeared as a grey fuzzy.

From my highly light polluted porch (chicago suburbs), the nebula
appears very clearly green. (I am not using any filters) None of the
pictures I have seen show it as green.

Is this the real color? (visible wavelengths) Or perhaps is it that my
eye is just more sensitive to green and not getting enough light to see
the other parts of the spectrum? Or possibly just a funny result of
light pollution?

Mark