Pollen Corona About the Moon
November 19, 2008
This impressive lunar corona was photographed near Vallentuna, Sweden on May 20, 2008. Tree pollen rather than minute water droplets are responsible for its formation. Coronae result from the interference of sunlight or moonlight diffracted around the outside edges of tiny particles. Note that irregularly shaped pollen grains produce irregular rather than circular shaped coronae. Pollen counts greater than about 2,000 particles per cubic meter are needed in order for pollen coronae to be observed.
Photo details: Canon EOS 450D camera; 75-300 mm Carl Zeiss objective lens; at 107 mm; ISO 400; f/5; exposure of 2.5 seconds - 1/4000s; combined in Adobe Photoshop CS2 Windows.