On the night of 22 December I saw this very striking halo around the moon. It's a circumscribed 22-degree halo, where the more common circular halo is surrounded by an oval one. Apparently you get these when the moon (or sun) is high in the sky and also the ice crystals in the cloud are preferentially laying horizontally. At UK latitudes these criteria are not often met, so it was quite a rare sight for me.
The exposure was 15 seconds, f/5.6, ISO400, on 40D with the EF-S10-22mm at 12mm. Just above the moon are Castor and Pollux, and you can see Orion in the bottom right corner.
