Inzilbêth of the Dúnedain

I was on the road very early this morning, a good hour before the first hint of dawn appeared in the sky, as I had to take two steers to the butcher. It was pouring with rain but the moon was almost a full one and it wasn't obscured by the rain clouds. Suddenly, up ahead, I saw a rainbow, or rather what i thought was a rainbow except of course there was no sun. Then I realised it could only the moonlight which have caused it to form. It's obvious really, but this is the very first time I've ever seen what is apparently called a moonbow, inspite of, over the years, spending a good deal of time outdoors after dark . The photo is a googled one but the beam looks exactly like the one I saw.

It got me wondering just how common or otherwise these things are and how often other people see them.