Crystal type:
- Pyramidal crystals
- random
- Refraction at 2 pyramidal surfaces
Occurrence:
- very rare
Description
The 20° ring is a faintly colored ring of light with a reddish inner edge and a radius of 20° around the sun. It usually occurs with other halos such as the 9° ring , which are created by pyramidal crystals. The 20° ring is the third inner ring of the halo rings created by pyramidal crystals. It is also called Burney's halo.
Origin
The 20° ring is formed by randomly oriented pyramidal crystals. The light passes through two opposite pyramidal faces at the same end of the crystal, which enclose an angle of 56°. The graphic above shows the light path.
Photos
Pyramidal halos with 20° ring (Photo: Elmar Schmidt)
Pyramidal halo with 20° ring (Photo: Elmar Schmidt)
Pyramidal halos with 20 ring on 03/26/2013, Dresden (Photo: Alexander Haußmann)