Pollen coronas are produced by light scattering at pollen grains. The shape of the corona patterns depend on the geometrical form of the pollen grain.

The photograph was taken by Jari Piikki near Juva, Finland at a day of high pine pollen concentration. Sorry for the bad reproduction quality. The sketch shows the MickyMouse-like form of pine pollens.

Approximating the form by three ellipsoids we calculated the Frauenhofer diffraction amplitude for strong vertical orientation of the pollen body axis (see sketch) for different altitudes of the Sun.

There are still a few reprints of the paper with all plates of the special issue "Light and Color in the Open Air".

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Eberhard Traenkle

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