A couple of days ago birch started flowering in Southern Finland and pollen coronae appeared in the sky. I photographed this corona yesterday and here is a composite of six individual images taken in one F-stop intervals and merged together with the HDRI-technique. The photo was enhanced rather heavily by applying unsharp mask and hue adjustment.
More natural version of the same photo is here. Another HDR-image of birch pollen corona, taken by Timo Kuhmonen, is here. See also the pollen corona around the moon by Jari Luomanen.