The 13th Zodiac sign

[Kiskimos]

perhaps i have come to the wrong place to ask this question, ill go ahead anyway ...the other week i looked up into the sky and the moon perfectly central in a large circle of space in which there was no cloud, surrounding it (obvioudly) was cloud. i tried to take a photo of it but i havent got the film developed yet.the moon was perfectly Horoscope and edge of the circle around it was crisp and neat .i wondered if anyone might know the name of such an occurance or anyone else had seen one ?