I was in the French Alps the other day, high in the mountains (not sure if this is relevant), and, on the night of a full moon, with mist in the sky, there was a circular ring of light around the moon. The ring subtended an angle about 5 times that subtended by the moon (that is to say, it looked about 5 times as wide as the moon), and, the colours were split up (though not as well as in, say a rainbow - they sort of merged together a bit). The inside colour was (I think - may have forgotten) red. Rainbows appear on the 'other side' of the sun, due to the geometry of the spherical raindrop, so it certainly wasn't a standard rainbow. Also, it subtended far too small an angle (I could easily see the whole ring, with the moon at the centre) Any ideas what was happening?