are visible much more often than rainbows, usually at least once or
twice a week. To find them successfully, shield the eyes from excessive
glare and know their sizes in the sky.
Shield the sun
Halos are much more easily seen when the sun is shielded. Use a building,
a tree, a post or a hand. Always shield both eyes and never look directly
at the sun.
22� halo and fragment of upper tangent
arc. Sun 20� high 27th April 01. �Bob Fosbury
The most common is the 22� radius circular halo. It is easily found
in the sky. Stretch out your arm and spread your fingers wide. The
distance from the thumb to the tip of the little finger is then about
20�. Cover the sun with the thumb and the 22� halo will be near the
tip of the small finger.
circular halo and circumscribed halo. 21st May 01
Sun elevation 57�. Photo Les Cowley