Circumscribed Halo Above Curitiba, Brazil

November 06, 2018

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Photographer: Fabiano B. Diniz
Summary Authors: Fabiano B. Diniz; Jim Foster

Shown above is a 22 degree halo and a colorful circumscribed halo as observed from Curitiba, Brazil. The oval-shaped circumscribed arc can be seen tangent to the inner, circular 22 degree halo directly above and below the solar disk, once the Sun climbs higher than about 29 degrees above the horizon. But the shape of the circumscribed arc varies with change in the solar altitude. Like nearly all such halos that change shape as the Sun moves higher or lower in the sky, it's formed by spinning ice crystals in cirrus clouds.

A careful analysis of this image also reveals a dim fragment of an infralateral arc (at far left) and a faint portion of the parhelic circle (extending from the Sun to the upper left corner). Photo taken on September 29, 2018.

Photo Details: Camera: Canon EOS 6D; Software: Adobe Photoshop CS6 (Windows); Exposure Time: 0.0016s (1/640); ISO equivalent: 100.