Comet Catalina was discovered in October 2013 by researchers working on a project designed to find comets and asteroids that might collide with Earth. This is your one and only chance to see this comet because it is now on its outbound journey to out of the Solar System. Once it leaves it’s gone forever. Binoculars are needed to see this comet. It will make its closest flyby in Northern Hemisphere on 17 January 2016. Comet Catalina is expected to move within 0.4 degrees. If you take your fist and hold it out at arm's length up against the sky, from the top knuckle to the bottom knuckle that's about 10 degrees, so about a fist's width above Venus, that's where the comet will be". Comet Catalina will be bright in the dark sky and you might be able to watch it naked eye but you have to prepare yourself with some kind of binoculars or a small telescope.
The Sky and Telescope website has an incredible map of the night sky that’ll help those of you in the Northern Hemisphere find it easily.
Plait explains that where Catalina has been for the past million years. He says “Catalina is coming from very deep space, probably out in the Oort cloud. Its orbit may have originally been millions of years long. Perhaps a star that passed a couple of light years away a million years ago, or the tides from the galaxy itself - and dropped it toward the Sun. That means it has enough energy to escape from the Sun and is on its way out of the Solar System forever (this is technically called a hyperbolic orbit)."
If you want to see this particular comet it is the time to do this. So don’t let this one go because it’s not coming back.