Distortions of the Rising or Setting Sun and Moon

Verformungen von Sonne und Mond beim Auf- und Untergang 

Sun rise and strong distortions above atmospheric inversation layer.
Photo: © Harald Wochner

At low elevations the sun, or even more seldom, the moon often show up strange distortions. Even planets like Jupiter or Venus sometimes are distorted in shape of a line when they rise or set. The reason for this is nothing more than a mirage caused by two or more layers of air of different density which kind of �bend� the ray of light coming from the sun at the dividing line between these two layers of air.

There are two different kinds of these mirages:

• If the lower layer of air is warmer than the upper one (e.g. in case of a ground inversion) the reflection of the sun first lies on the outside of the reflecting line and later merges with the sun. Finally the sun and its reflection disappear behind the horizon.
• If the air on the ground is colder (e.g. over watery or icy surfaces) the line of sight is bent in such a way that you can look beneath the horizon. So the sun and the moon can still be visible when they are already behind the horizon from the astronomical point of view. In this case it is characteristic that there is a so�called �vanishing line� because the observer does not receive any light rays from this angle.