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Pollen Coronae in February 2019

On February 24, th 2019, the weather at Trier was very clear and windy, after a period of exceptionally warm days. The press and internet forecasts reported very high pollen levels, especially from alder and hazel. In the early afternoon coronae could be observed, they got even stronger in the evening. They were clearly oval with characteristic patches. Pollen corona are formed by the scattering of light by small airborne particles.They are an interference phonomenon. The dimensions of the coronae agreed well with corona calculations based on diffracting particles of alder pollen size (see www.atoptics.co.uk/fza168.htm). I was able to examine alder pollen with the help of a microscope a few days later. The pollen is bun-shaped when it is fresh and later on shows roughly pentagonal detail.


Leica M, Summarit-M 90 mm f/2.5, 1/3000 sec at f/4.8.


Alder pollen, already drying.

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