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Upside down 'rainbow' spotted in the sky

Rachel Sanders An upside down "rainbow" seen against a clear blue sky.Rachel Sanders
The upside down "rainbow" is more common that you would think

An upside down "rainbow" has been spotted in the sky above Essex.

Rachel Sanders spotted the circumzenithal arc in Gosfield, near Halstead, on Monday.

The Met Office said the phenomenon was a type of halo formed when sunlight refracts through horizontal ice crystals, at such an angle that light enters through a flat top face and exits through a side prism face.

It said the arcs were "actually quite common", being commonly associated with Cirrus clouds that form throughout the year. "However, we only sometimes see them as they are usually obscured by clouds underneath," it added.

Rachel Sanders An upside down rainbow seen against a clear blue sky. There are treetops showing to the left and right of the image.Rachel Sanders
The arc is not rare, but is often obscured by clouds
Rachel Sanders An upside down rainbow which is an optical illusion, seen against a blue sky with wisps of white clouds. Rachel Sanders
Best of luck finding the pot of gold that high up

While they may be relatively common, a special set of circumstances are required for them to form.

The sun needs to be more than five and less than 32 degrees above the horizon, in order that the sunlight can refract in the correct way through the ice crystals to form the smiling, rather than frowning, halo.

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