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Fire Rainbow a.k.a Circumhorizon Arcs

At the very outset, I wish to mention that this image was not photoshpped.


Fire rainbows, scientifically known as circumhorizon arcs, can be seen during summer solstice when it is close to noon, around two handspans away from the sun.


The arc is produced by plate oriented crystals and is a close relation to the circumzenithal arc. Light rays enter the almost vertical crystal side faces and leave via the lower horizontal face (ray path 3-1).


The refraction of the almost parallel sun’s rays through faces inclined at 90° produces pure, bright and well separated prismatic colours ~ purer than those of the rainbow. The colours are at their best when the crystal tilts are smallest. Large crystal tilts produce more pastel hues.


Link www.atoptics.co.uk/halo/cha2.htm

www.atoptics.co.uk/halo/chaim0.htm --- Circumhorizon Arc Gallery


(Photo: Marc Sorensen)


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Taken on March 16, 2009