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© Copyright 2000, Jim Loy
Astronomy books often contain very colorful photos of
stars, nebulas, clusters, and galaxies. Look up in the sky and it is mostly
black and white (with a few reddish points). Look through your telescope and
you still see mostly black and white. Why is this?
There are two reasons for this. One reason is that your eyes cannot detect color of very dim light. The color photoreceptors (cones) in your eye cannot respond very well to dim light. See Color Vision. The other reason is that the colors are very subtle, and must be enhanced. This is normally done by freezing the film. Amateur astronomers can buy cameras into which they carefully put dry ice (solid carbon dioxide, which can freeze your skin in seconds).