Snake Valley Halo - Imaged by Ken James (Snake Valley Astr. Assn.) at Snake Valley, Victoria, Australia on Jan 9, 2009 when the sun was a summer's 73° high. ©Ken James, shown with permission.
It is a 22� halo rather than a high-sun circumscribed halo because at the solar altitude of 73� the latter would be measurably oval. Another guide is that its colours are diffuse and pastel. Those of the circumscribed halo are slightly sharper and more saturated.
The halo nicely shows the 'hole in the sky' effect. Rays passing through hexagonal ice prisms and contributing their glints to the halo are deviated a minimum of 22�. Many rays are deviated through greater angles but none less. The absence of crystal glints within 22� of the sun makes the sky noticeably darker there - a hole in the sky.
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