Solar Halo Over Boca Raton
July 13, 2005
While out to lunch in Boca Raton, Florida on May 17, 2005, I noticed a dazzling solar halo directly above me in the noon sky. I couldn't wait to get back to my office and get my camera to capture it. I took numerous pictures, trying to get just the right exposure. A full halo can only appear when hexagonal ice crystals in cirrus type clouds are more or less randomly oriented and the Sun's elevation above the horizon is greater than the angular radius of the halo (in this case 22 degrees). The minimum deviation of sunlight through the 60 degree prisms (crystal faces) creates the 22 degree halo.
Photo details: A Canon Digital Rebel XT camera was used, with the kit 18-55 lens, at 18 mm (35mm equivalent = 28mm). It was taken at 1/4000s of a second (I believe) at f/11, with an ISO of 100. I used a circular polarizer, UV filter, and a neutral density filter. In Photoshop, I tweaked the levels and contrast, as well as added a bluish cast to create the final effect.Related Links: