A 22° Halo like this is visible when thin cirrus clouds made of ice cover the sky and the ice-crystals in the clouds are oriented properly.
To the lower left of the Halo you can see the constellation Orion.

Camera	Nikon D200
Lens	Tokina 12-24 /4 at 12mm
Exposure	15sec. at f/4 ISO 360
Date:	21 February 2010