As the title of the photograph suggests, this picture is of a full-moon and a circular “rainbow” circling the moon with concentric rings of light and colour. While the effect on a clear night is simply beautiful, the physics behind the photo are very simple.
According to Wikipedia, the optical phenomenon which produced this “werewolf rainbow” is known by meteorologists as a corona. It is produced by the diffraction of light (in this case, from the Moon) by tiny ice crystals and water droplets in the clouds. Apparently, these only occur when there is a certain amount of water or ice in the atmosphere; if too much moisture is present, the corona will be obscured, while if too little is suspended, insufficient amounts of atmospheric diffraction will occur.
In any case, the corona certainly brought one particular photographer/physicist some amusement, fascination, and frozen fingers on a cool November night.