In the following picture you will see a very interesting phenomena. The plane is above the clouds with the sun behind. You can see a shadow of the plane, but the more significant thing is the perihelia around the shadow. It was the day for that image. I had several opportunities for pics and I took a little film as well. You can see two distinct rings in the pic. The plane has a relatively sharp edge and the diffraction caused by the plane produces a nice series of rainbows projected on the clouds, I think. Very nice.
