Some of my earliest stargazing memories involve the same seven stars. Whether you call it the Plough or the Big Dipper – or even the saucepan, the panhandle or the wagon – the stars that form this asterism are ones I think many people learn to recognise from an early age. But just because most people can recognise the Plough, and, by extension, Ursa Major, the constellation in which it lies, doesn’t mean we have explored everything in this patch of the sky. And May is as good a time…