I was in Cambridge (England) yesterday, on a clear bright and almost-but-not-quite cloudless day. I was wandering along back streets and alleys with my camera, looking up at the roofs for non-tourist things to photograph (and risking a serious push-bike accident). In one particularly tall and dark alley (don't know the name, but close to King's College) I saw, almost overhead and in the same direction as the sun, a streak of rainbow. It was wide enough to show all the colours and about three or four times as long. These rainbows are caused by ice-crystal clouds. I'm not sure of the fine details of how it works, but the angles are very different from the rain-generated rainbow and the colours can be the wrong way up, with red on the inside of the curve. I think this is what's called a "sun-dog". I don't know where they can appear -- when you get a double rain-rainbow, the two bows are very cose together, the second one outside the main one and the colours upside down.

I didn't photograph it, because it was faint and I didn't think it would show up well.

Steve