Last updated at 09:42 07 August 2007

So where, you might wonder, would you find the crock of gold?

That's what the myth says you will discover at the end of the rainbow. But sadly for treasure-hunters, this one has no end. It is a perfect circle.

This awesome sight in the skies over Malaysia yesterday wasn't really a rainbow at all but a rare optical illusion called a sundog.

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These appear when the sun is low in the sky and its rays catch the thin vapour formed of ice crystals which lies in the atmosphere six miles above the Earth's surface.

The rays are refracted by the crystals to produce what looks like a halo round the sun.

Sometimes, as here, they display a spectrum of colours from red closest to the sun to a pale blue furthest from it, which has led to them being mistaken for full circle rainbows.

In centuries past, they were thought of as signs of ill omen. These days they are most often mistaken for UFOs.