Tuesday, January 13, 2015

Sun Dogs


The recent mass of arctic air over Indiana has kept me away from the scope, but there are still interesting things to see in the sky. This image was snapped last Friday while I was driving southbound. The sun is low in the SE and  the sun dogs and arc are clearly visible, despite the fact my camera insisted on focusing on the windows, rather than at infinity. Hexagonal ice crystals in the atmosphere act as prisms and bend the sun's light. The geometry of the crystals bends the light witha minimum deflection of 22 degrees. Random orientation of the crystals produces the 22 degree halo that can be seen extending from the dogs.