This week, track down the asterism known as the Great Diamond. Asterisms are patterns of stars that exist alongside the officially defined constellations. In this case, the Great Diamond consists of four stars. Cor Caroli in Canes Venatici, the hunting dogs; Denebola in Leo, the lion; Spica in Virgo, the virgin; Arcturus in Boötes, the herdsman.
The chart shows the view looking west at midnight from London tonight. The best way to find the Great Diamond is to identify the Plough asterism in Ursa Major, then follow the curve of the handle across to Arcturus. From there, find the bright jewel of Spica, then the more subdued Denebola, and finally the fainter Cor Caroli.
Observers in the southern hemisphere will find the asterism in the north-west during the night. Spica will be at the greatest altitude, and Cor Caroli at the lowest. Having located the asterism, look inside to identify the faint constellation of Coma Berenices, Berenice’s hair. It was named after Queen Berenice II of Egypt, who sacrificed her hair as a votive offering to the gods.
