This week’s constellation is a pure delight. Delphinus, the dolphin, is one of the smallest, faintest constellations in the sky, but once seen it is impossible to get the image of a celestial dolphin jumping up from the Milky Way out of your mind.

The chart shows the view looking south-west from London at midnight on Monday. Use the bright star of Altair in Aquila, the eagle, to orientate yourself. You will need to find a dark site as only Sualocin and Rotanev are above magnitude four in brightness.

Defined by Ptolemy in the 2nd century, Delphinus has several myths attached to it. In one tale, Delphinus is said to have been the go-between who brokered the marriage between Poseidon and the (eventual) sea goddess Amphitrite, when the latter fled from Poseidon’s advances. In gratitude for helping him land his wife, the god placed Delphinus among the stars.

In another story, the musician Arion was voyaging back to Greece and the sailors were plotting to rob him. Arion sang one last song, which summoned dolphins to the vessels. He then stepped overboard and was carried back to Greece by one of the animals. Apollo created the constellation in gratitude to the benevolent dolphin. From Sydney, Australia, look for Delphinus in the north-western sky.