Rainbows & Antisolar Rays

Image by Jürg Alean (Swisseduc.ch, Stromboli online) over the Rhine at Eglisau, Switzerland.

©Jürg Alean, shown with permission
A bright primary rainbow bridges the Rhine with fragments of an outer reverse colour secondary bow. The sky is dark between the bows - Alexanders dark band.

Dramatic antisolar rays and shadows converge down towards the rainbow centre, the antisolar point. At left the shadows form rainbow spokes.


Raindrops near the surface of the 'rainbow cone' form the primary bow's outer coloured rim. The cone axis extends from the eye towards the antisolar point.

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Long parallel shadows cast by clouds with bright sky between them generate the antisolar (anticrepuscular) rays and shadows. Their apparent convergence is purely due to perspective.

Sometimes a cloud shadow intersects the rainbow cone. Raindrops within the shadow cannot contribute to the rainbow. Part of the bow is blotted out and a dark 'spoke' can extend inwards towards the bow centre. Several clouds and spokes make a wheel which often revolves as the clouds move.