22 Degree Halo Above Martinique

May 28, 2005


Provided and copyright by: Philippe Taieb , Centre de decouverte des sciences de la Terre
Summary authors & editors: Jim Foster; Philippe Taieb

This magnificent 22 degree halo was photographed on April 19, 2005 from Saint-Pierre en Martinique. Though cumulus clouds clutter the sky, high altitude cirrus clouds, composed of hexagonal ice crystals, are responsible for this halo, as well as most all halo phenomena. If these crystals are relatively randomly oriented, a 22-degree halo may be observed, as was the case this afternoon. When sunlight passes through crystals not having a preferred orientation, there's a concentration of light rays deviated by angles of approximately 22 degrees. So in order to see a 22 degree halo, you need to look about 22 degrees away from the Sun -- about 2 fists held at arm's length. Note that because the colors are so bright, this may actually be a circumscribed halo (see Atmospheric Optics link below).

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