What size of a telescope is need to see the color in Orion Nebula?

Question

I saw kinda of greenish glow in Orion with 10 inch telesocpe. However, I expect to see much more in color and brighter. I know it won't look exactly like in the photograph, but I would like to see it as close as it can get like in the photograph.


What size of Dobsonian telescope would do it?

Answer 1

No telescope, no matter how large, can let your eye alone see those colors. Even if you were in a space ship right next to the nebula you could not see those colors. The light is too dim for human color vision to work. Only long exposure photography can capture color in such faint light.

Answer 2

The human eye's ability to see color in nebulae is limited to the nebulae with the highest surface brightness. The human eye is most sensitive in the green region of visible light. So most nebulae that are bright enough to show color beyond shades of grey will show some blue-green hue.



Back in the '90s when I was younger and lived in very dark skies with a 10" scope, I routinely saw blue-green in the Orion nebula. *Occasionally* I saw a little more like purple-pink, but it was *very* subtle.



Those who say that you cannot see any color in M42 with only a 10" are either wrong or less sensitive to seeing color than others might. But it will NEVER be like in the photographs or even close in terms of color saturation.



Color aside though, the human eye often sees more structure in the nebula's central regions than in many photographs because the central region gets overexposed.



Many bright condensed planetary nebulae will show a distinct blue-green color. These include the "Blue Snowball" mentioned by Thomas, as well as NGC 6543 the Cat's Eye nebula, as well as NGC 7009, the "Saturn Nebula" and several others.

Answer 3

The photographs are greatly exaggerated if not outright false colour. The red that's often in the photo, for example, is from a specific wavelength of light called hydrogen alpha, and that's in reality a very deep red that our eyes can't see well. We see the green oxygen III and blue hydrogen beta wavelengths much better, which is why the nebula can look greenish to our eyes.



As GeoffG mentioned, very few nebulae show colour. Your best bet is with bright planetary nebulae, since they have higher surface brightness (their light comes from a smaller apparent area). People have reported NGC 7662, the "Blue Snowball Nebula", was indeed distinctly blue in an 8 inch scope for example.

Answer 4

In 58 years of observing, I have seen colour in a nebula exactly THREE times, but never in the Orion Nebula. In each case I was using a very large telescope: 18-inch (Eta Carina Nebula), 22-inch (Dumbbell Nebula) and 74-inch (Snowball Nebula). It was so unusual that I vividly remember each observation. Unfortunately, I have never observed the Orion Nebula with any aperture larger than 12-inch, so can't say how much is required. Adjust your expectations, if you don't want to be disappointed all your life!

Answer 5

You are not going to see color in the Orion nebula no matter how large of a telescope you have, at least in terms of what is practical for amateur astronomers. You could, however, improve the contrast of the object using a narrowband nebular filter. The Orion Ultrablock filters are a popular choice, and they are currently on sale. See http://www.skiesunlimited.net/SPD/orion-ultrablock-filters--ia1364411545780.jsp