BBC Sky at Night Magazine
3. SOUTHEAST AND EAST
As we cross into the southeast, we’re in the rising part of the sky, where the newcomers are. Here, we’ll find the Great Square of Pegasus. Its eastern-most star is Alpheratz, which is the brightest star in the constellation of Andromeda, the mythological princess. Andromeda’s main stars lie more or less parallel to the horizon, like they’re underlining the upper sky. Two star hops east (toward the left) of Alpheratz is Mirach (not to be confused with the Plough’s Merak).
If you have a pair of binoculars, aim them about 7˚
– a bit less than a fist at arm’s length – above Mirach. Hiding 2.5 million lightyears away in that seemingly empty patch is the Andromeda Galaxy, M31. Under city and suburban skies, it looks like a thumbprint on the sky and might surprise you the first time you spot it. Once you see it, though, you’ll go back again and again.