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The Trapezium is a group of stars and not nebulosity. A red filter should show them as red. There is also some reflection nebulosity intermixed with the emission nebula in M42, so scattered red continuum light from the stars may also play a slight role (along with H-alpha). The area immediately around the Trapezium (the "Huygenian" region) is somewhat bluish or bluish-green to me, with slight variations in saturation and hue. I have to look much farther away to note the pinkish or faint reddish coloration. One area which shows it to some degree is the southeastern "wing" of the nebula. There is a strip or filament just off the southwest edge of the southeastern wing which is sometimes seen as reddish. The other areas are again subtle pinkish tones which appear in vague patches somewhat outside the Huygenian region but not all the way out to the outermost edges. In scopes larger than 10 inches, on a good night, some subtle pinkish tones are visible, although again, as I pointed out, not everyone will be able to see them. Most people can see the bluish-green core of M42 even in some fairly modest apertures, but often much beyond that, there is usually little distinct coloration visible unless the aperture is considerable.

As for NGC 7662, that object is mostly an OIII emitter, and I don't see any red in it, at least in my 10 inch. As I indicated, the planetary nebulae which tend to show at least a little red are IC 418 and Campbell's Hydrogen Star. Most of the rest tend to have either a bluish-green color or no prominent color at all.

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My experience has been almost exactly the same as David's with the exception that the smallest aperture that I have seen blue, green, and muted pink hues within the previously stated areas of M42 has been 14.5 inches. It's far easier with 20 and 25-inch apertures. Every time that I've detected such color the conditions have been exceptional.

When using a 30-inch on a very good night a couple of years ago, I noticed a faint pink glow within M8.

I've also seen IC 418, the Raspberry Nebula, display a hard-to-describe ruddy color through large apertures on some occasions.

The Homunculus Nebula that surrounds Eta Carinae was a very distinct orange color as seen through a 22-inch Starmaster at an altitude of 4,000 meters in Bolivia.

Planetary nebulae such as NGC 6543, NGC 6572, and NGC 7662 seem far more colorful to me through large apertures.

Dave Mitsky

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