Another corona around the Moon

 

The Moon was shining through high cloud producing a clear corona. To my eye, there was a clear red outer edge to it but viewing the photos, you'd take some convincing. I re-read this article about the phenomenon. I'm not sure I'd noticed before that this diffraction pattern is an Airy Disc. I know the Airy Disc as the bright central view through a circular aperture such as a telescope. Unlike with the refraction halos, there is not set angular width here apparently, as it depends on the droplet size. Given that the Moon subtends 0.5 degrees at the eye, I'd say here the corona subtends 1.5 degrees.