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  • For light to enter the cirrus cloud crystals at just the right angle to make a circumhorizon arc, the sun must be at an angle of at least 58 degrees above the horizon.

    Celestial Phenomena

  • A circumhorizon arc only forms when the clouds contain a specific, hexagonally shaped ice crystal.

    Celestial Phenomena

  • Several very specific conditions must exist in tandem for a circumhorizon arc to occur.

    Celestial Phenomena


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