Elliptical halos ~ "Really difficult to shoot, fleeting stratus fractus kept crossing the Moon and, of course, a corona was visible."
Elliptical halos, here ~1.5x2.5° (moon 45° high) remain enigmatic. They are rare and their size varies between occurrences and moon/sun elevation. They can be modeled - but not very well - by invoking very flat pyramidal crystals but these are not crystallographically realistic. Larger cluster or sterically hindered/strained dendritic crystals are other possibilities. The 6-pointed star is a camera aperture blade artifact, the lens had to be considerably stopped down.