The best-known (and coolest) of these phenomena is the rainbow
but there are lots of others - some of them are every bit as common as the
but they are not as well known.
Sun dogs: These are most commonly seen at sunrise or sunset and take the form of two (sometimes only one is visible) phantom suns - one on either side of the real sun. The phenomenon is caused by refraction of the sunlight through ice crystals in high cirrus clouds.
photo courtesy of Wikipedia article.
If there is enough cloud, the sun dogs sometimes extend to form a complete arch or ring around the sun - you can see parts of the arch in the above photo.
Many people haven't seen (or even heard of) sun dogs, but they are very common - more common than an 'ordinary' rainbow. If you want to see them for yourself, wait for a day with mostly clear skies and just some high wispy cloud and look out for them around sunset or sunrise. As always, avoid looking directly at the sun itself as this can cause permanent eye damage - use a piece of paper or similar to cover the sun while looking for the sun dogs on either side.
Atmospheric optical phenomena
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