UK High Sun Halos

The sun has been a rare UK sight this summer. High sun halos come much rarer. This bright display was captured by Michael Coupar over Lancashire, England at around noon on 9th August '12.
 ©Michael Coupar, shown with permission.

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The sun in the cirrus streaked sky was 49° high.

A bright white parhelic circle from plate and column crystals passed through the sun and extended some 120° around the zenith.

The coloured arc curving around the sun is a fragment of a circumscribed halo. Horizontal column crystals make the halo which is the high sun version of upper and lower tangent arcs.

Showing weakly inside the circumscribed halo is a 22° halo fragment.

The slanting prismatic patch on the parhelic circle is a sundog. The high sun and consequent skew angles through plate crystals has shifted it well away from the 22° sun distance oft quoted for sundogs.

At right a HaloSim ray tracing shows what a more complete cirrus sky coverage might have shown. But beauty often comes from incompleteness and asymmetry. The Lancashire display was of enough rarity and beauty.