Yes unfortunately all the vibrant colours you see in astrophotography are very much enhanced, either by the use of long exposure, or often using a colour such as red to represent non-visible light like infra-red, or purple for x-ray light.
That said, it is possible to see colour with the eye, but just not a lot of it. Some nebulae have a blueish tint to them, others green, others a slight pink, but certainly they don’t jump out like they do in the images.
One of the reasons they seem so grey is because they’re so diffuse. The colours are there, but there’s so little light hitting your eye that it isn’t enough to trigger the cone receptors (which deal with colour) in your retina, so you see the image with your rod receptors instead.
That’s also why with a large telescope it can be easier to pick out colour – since more light is collected and focussed, it has more chance of triggering the cones and so enabling you to see the hues a bit better.
- This reply was modified 3 years, 8 months ago by Mark Galvin.
Arthur Dent: "But what is it? What’s worth a statue fifteen miles high? "
Bird: "It was of great symbolic importance to our ancestors, it’s called ’Arthur Dent Throwing the Nutrimatic Cup’. "
Arthur: "Sorry, what did you say?"