How to find Hydra, the biggest constellation in the sky

Named after a water snake, Hydra is a large constellation, but it isn’t very bright. Finding it will take really dark skies – and tapping into some of astronomy’s top visualising tips, says Abigail Beall

MAKE a fist with your hand, then hold it out to the sky at arm’s length. The width covered by your fist will be around 10 degrees. Now imagine 10 of these in a row. The biggest constellation in the sky, Hydra (pictured right), stretches across this huge expanse, covering 102 degrees.

Named after a mythical water snake, the constellation’s head sits in the northern celestial sphere while its tail stretches into the southern one. This means that the entire constellation can be seen from many places around the world, anywhere located between 54 degrees north and 83 …