This halo measures circular and its colours are pastel and diffuse. The sun was 53° high. It is fairly certain therefore that it is a 22 degree halo from hexagonal prisms of some type randomly oriented in the high cirrus cloud.

When the sun is high, the circumscribed halo generated by horizontal column crystals is often mistaken for a 22 degree halo.

Unless there is a 22 degree halo actually present for comparison it can be difficult to detect the circumscribed halo’s departure from circularity. A better guide is sharpness and intensity of colour – the circumscribed halo has brighter and more distinct colours.

22° Halo imaged by Aurélien Astoux in Antibes in the South of France. ©Aurélien Astoux, shown with permission.


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