Gegensonne (EE17)

On the horizontal circle, in rare cases, a brightening can be seen opposite the sun. This whitish brightening is called counter sun.

The formation of the anthelion is still disputed. According to the view of W. Tape, the anthelion is not an independent type of halo. The brightening comes about because several halos intersect at the point opposite the sun. It involves the circumhorizontal arc, the diffuse anthelion arcs, as well as the anthelion arcs of Tricker and Wegener. Except for the circumhorizontal arc, these types of halos require almost ideally horizontally oriented column crystals. Therefore, according to this theory, the anthelion should appear together with other column halos if the ice crystals are dispersed across the sky. However, the anthelion has also been observed without other column halos. This could mean that the anthelion is indeed an independent type of halo. According to Visser, the anthelion forms in quad prisms with two vertical side faces. In this process, the sunlight is reflected twice externally on the prism surfaces and then reflected back at an angle of 180°. Another explanation comes from Greenler, suggesting that the anthelion forms in column prisms, where the light is reflected twice inside the crystal.