I stepped outside to let the dog out last thing at night on the 17th February to be greeted by the spectacular sight of a huge Moon halo. This is not a rare phenomenon, especially given the propensity for high hazy cloud in Wiltshire, but I have rarely seen such an impressive one. I nipped back inside, grabbed a camera and took a variety of shots - this is my favourite one. The halo, also known as a 22° halo as it covers about 22° of sky, is caused by the refraction of moonlight in millions of hexagonal ice crystals suspended in the atmosphere.