Sometimes something wonderful happens when you least expect it. If I had gone looking for this I never would have found it. But a viewer called at work, asking what the black ring around the sun was. I ran outside and here it was! The ring is called a 'halo' - and is caused by sunlight passing through the ice crystals that make up the cirrus clouds which occasionally pass through the upper part of the atmosphere. The ice crystals act as prisms, bending light and separating it into it's component colors. Because the sun's rays spread out in a cone shaped pattern, we see the resulting effect as a 'ring.' Thanks for the explanation, Jeff Renner! And thanks for the phone call Patty!