|Subtle Corona ~ Pictured by Victor von Salza (photostream) at Vista House, Oregon on a foggy Autumn morning. ©Victor von Salza, shown with permission.
Light diffracted by small water droplets produces a corona. Each point on a drop periphery scatters light to form outward going trains of spherical waves. The waves from different points overlap and constructively or destructively interfere to form, at some distance away, the coronal diffraction pattern of a central aureole surrounded by rings.