Re: (IAAC) Obj: M 42, Trapezium - Inst: 25" Obsession

Interestingly, I noted color in M42 from a very dark site with as small an 
instrument as 10x50 binocs (see IAAC archive). It seems generally that color is 
either visible in M42 from a given site, or it isn't:  I've even missed the 
faint green hues with the 20" from only moderately dark sites!
As for reds, I remember reading (probably in Roger Clark's book) that much of 
what we often note as "pale green" is actually other colors (such as red) 
stimulating the rods JUST over the threshold for color perception. This effect 
is very common in meteor observing, where meteor "heads" or persistent trains 
are most frequently seen as pale green, if color is seen at all.
I've seen red tinges with the 20" at very dark sites, but suspect they probably 
would have been visible even in smaller scopes. Todd Gross (an active poster to 
IAAC) has also logged "red/pinks" with a 16" dob:
Clear skies!

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