English: Footer: The observe only sees light coming from a specific group of crystals that are at an angle of about 22° relative to the line of sight towards the sun or moon. No angles in this image have been exaggerated

In this illustration the hexagons represent a cloud of ice crystals. Only a specific group of them direct light of any significant intensity toward a given observer. The dotted lines in the illustration represent light that is not entering the eye of the observer while the two solid red and two solid blue lines represent the light at the two extreme edges of the spectrum that do enter the observer’s eye.
The group of ice crystals directing light into the observer’s eye, while appearing circular from the point of view of the observer, in fact have a three dimensional cone shape stretching into the cloud of crystals. This group of crystals can be further divided into smaller groups depending on the color of the light they direct into the observer’s eye. The cone of crystals directing blue light toward a given observer has a slightly larger internal angle than the cone directing red light, this is because blue light is bent more by a given ice crystal.

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