Overview: Astronomers always get excited about comets and in December they are looking forward to something rather special. The snappily-named Comet C/2012 S1 ISON has travelled from the very edges of our solar system on a one way ticket around the sun. As it heats up there is intense speculation about whether it will develop a beautiful tail or just break apart. On the Canary island of La Palma the team use both the Liverpool and Issac Newton telescopes to go comet chasing.