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Paraselenae & Paraselenic circle - Sighted in Gloucestershire, England by Marcus Price. The moondogs were strongly coloured (see lower image) with their hues visible by eye. There is a hint of a 22 degree halo and upper tangent arc.    Images ©Marcus Price, shown with permission

Sundog/moondog colours arise from refraction and dispersion through what is effectively a 60° prism. 22° is a minimum deviation angle when the ray in the plate crystal is parallel to the intermediate side face. Other rays - as shown - are possible.

The result is colour overlap and sundogs/moondogs are never spectrally pure. Colours of shorter wavelength than reds overlap and become subdued.