I saw a pocket rainbow today. Its span was only 40m and it was in a field just 30m from me. Unfortunately, my cameras were 100m away where I'd put them down while I hunted rock art. By the time I'd got back to them and back to the spot the sun had gone in and didn't return :-(

I got to thinking that if this is a common occurance at this spot it could be the reason why someone marked it with some rock art ...