From the bank of river Moselle in Germany (Mosel), the town and spectacular castle of Cochem (Reichsburg, from the 12th century) appear at night. A colorful lunar corona forms as the night proceeds. The bright moonlight is diffracted by water droplets in thin clouds drifting in front of the lunar disk. This atmospheric phenomena have an intensely bright central aureole which is white-blue and fringed with yellows and reds. The corona can be 15 degrees or so in diameter and often it shrinks and swells as different clouds move in front of the moon.