Counter dawn
As a counter-dawn color are twilight phenomena in the sky above the sun opposite horizon - referred to before - the opposite horizon sunrise or after sunset by reflection of scattered sunlight in the atmosphere arise.
The orange-reddish and purple colors and their intensity can be quite different depending on the position of the sun, atmospheric components, altitude stratification, season and location. The reflection or counter-reflection in the sky above the opposite horizon comes about through backward scattering of the twilight light on air molecules. The path of this scattered light is particularly long, its strength low. Below the counter-twilight phenomena, the light-poor, gray-blue appearing earth shadow arc can be observed, blurred at the edge of the earth shadow by a purple color fringe, the main twilight arc or so-called Venus belt .
At a sun depth of 2 to 3 ° below the mathematical horizon , the counter-twilight usually reaches its highest intensity as the upper counter-twilight and the demarcation to the earth's shadow arc then blurs.
When the sun is 4 to 5 ° below the horizon, the rarer lower counter-dawn can be observed within the Earth's shadow arc. This is a pale reddish colored border that arises when a purple light that appears above the sunset or sunrise point is reflected in the opposite sky.
literature
- Brandt, Müller, Splittgerber: Observing the sky with binoculars. 2nd edition JA Barth-Verlag Leipzig 1984
- Marcel G. Minnaert: Light and color in nature . Birkhäuser Verlag, Basel 1992
Web links
- More photos in the weather dictionary at www.top-wetter.de
Individual evidence
- ↑ a b Marcel Minnaert: Light and color in nature . Birkhäuser Verlag, Basel 1992, ISBN 3-7643-2496-1 , p. 356ff.