Double Lunar Halo
What causes a double halo around
The halos around the moon and the sun are caused by
light reflecting through water droplets or ice
crystals in the atmosphere.
These halos form when light is separated into its
various colours by the prism effect of the six sided
ice crystals found in cirrostratus clouds. These
clouds are very high up in the atmosphere, usually
around twenty thousand to fifty thousand feet high.
Light is bent by the ice at an angle of twenty two
degrees, and so when they converge at the observer, he
sees a ring of twenty two degree diameter around the
sun or moon. The halo is pale, faintly coloured ring,
usually with red on the inside and blue on the
On rare occasions, a double halo can be seen,
sometimes with faint spokes, and it is caused by light
reflecting off water or ice.
Thanks for asking NEWTON!
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Update: June 2012