I just saw one! Obviously, it wasn’t bright like a daytime rainbow, but looking carefully, you could definitely see a spectral effect. I don’t remember ever seeing that before.
To try and describe the size, imagine looking up at a record album (you know, those things we listened to before CDs). With the full moon as the spindle hole, the rainbow was out at the edge. The moon itself also had an aura around it.
It’s slightly overcast here, so I know it has something to do with light refraction through water vapor. Does anyone know any better details as to the cause of this, or any links for information? Has anyone else ever seen this?