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Light Column below the setting Moon

Date:Mar.,1998 Instrument:f=28mm
Place: Pico Veleta, Sierra Nevada Observer:S. Kohle

© Copyright by the observers

The image above shows the setting full moon seen from the snowy 2920 m high Pico Veleta Radio-Observatory at morning dawn. The city Granada is illuminating the clouds from the valley.

The rare phenomenon of a lower light column can be seen below the moon. These columns are created by light reflection at horizontally oriented plate ice crystals in the atmosphere. Perfectly flat oriented crystals in a constant altitude below the observer and the light source would produce a reflected image of the moon. But the crystals show small deviations from the horizontal orientation and are also positioned at different heights. This leads to the elongated form of the reflection and if the light source has a low elevation above the horizon even to a column formed appearance. This effect is very similar with the light column that can be seen below the setting or rising sun on a water surface.

See also:
M.G.J. Minnaert: "Light and Color in the Outdoors", Springer-Verlag