Heiligenschein (German for ‘halo’ or ‘aureola’, literally ‘holy (or saintly) appearance’, pronounced [ˈhaɪlɪɡənˌʃaɪn]) (see also the article for halo, the optical phenomenon) is an optical phenomenon which creates a bright spot around the shadow of the viewer's head.
In photogrammetry and remote sensing it is more commonly known as the hotspot, and is due to the reduction in the proportion of shadows viewed at angles close to the backscatter direction. It may also be created when the surface on which the shadow falls has special optical characteristics. Both dry dusty surfaces and dewy grass are known to exhibit these characteristics. Nearly spherical dew droplets act as lenses to focus the light on the surface beneath them. Some of this light backscatters in the direction of the sunlight as it passes back through the dew droplet. This makes the antisolar point appear the brightest.
The glory creates a similar halo effect by a different mechanism.
- Aureole effect
- Subparhelic circle
- Opposition effect, the brightening of a rough surface, or an object with many particles, when illuminated from directly behind the observer
- Brocken spectre, the apparently enormous and magnified shadow of an observer cast upon the upper surfaces of clouds opposite the sun
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