Just saw and managed to snap a beautiful 22 degree moon halo. They are caused by the moon's light refracting through the ice crystals in the high clouds. In this case almost certainly thin cirrus clouds which are presaging the arrival of bad weather. Halos are not the same as moonbows, although they are often called that in error.
Will write more about them tomorrow if I get the chance, but wanted to get the photo up while I could.
Last night I stumbled across a name I have been looking for since a sailing trip a couple of months ago, when I took this photo. I now know that the unusual phenomenon in this picture is called a 'fogbow'. It is similar to a rainbow in many ways, but the fog droplets are so small that instead of light being refracted it is instead diffracted, which leads to a white arc instead of the more familiar colours. Coloured and white bows can occasionally be seen at night, if there are the right atmospheric conditions and a bright…