The eerie, unearthly sight of polar stratospheric clouds

I am something of a nephophile — and before you get all snickery and snarky, it comes from the Greek nephos, for "cloud"* — and I truly enjoy seeing images and videos of interesting and unusual clouds.

I live east of the Rocky Mountain foothills, and the wind patterns here generate a lot of unusual-looking clouds. I've seen all manners of them, including fluctus (another snicker-inducing name), mammatus (a snicker-inducing formation), lenticulars, and more.

I've also seen my share of iridescen...