Delphinus and Equuleus
the Dolphin and the Foal

Mythology - Poseidon was looking for a wife and chose Amphitrite, one of the Nereids. She refused him and hid herself in the Atlas mountains. Poseidon sent a dolphin to plead his case and she agreed to marry the sea god. She bore him three daughters: Triton, Rhode and Benthesicyme. The dolphin has since been immortalised as this small but cute constellation. Poseidon had many affairs and the offspring of one, Arion was a beautiful and talented bard. While in Sicily for a competition he won first prize and the envy of the sailors who were to bring him home to his patron, the tyrant-king of Corinth, Periander. Stealing his wealth and preparing to throw him overboard, Arion begged to be allowed to die as a bard, singing and playing his lyre. The music drew a school of dolphins to the surface to listen. Arion jumped into the water after singing his last and the dolphins allowed him to ride on their backs. They returned him to the shores of Corinth before the ship could reach port. The dolphin who transported him even threw itself onto the beach to be sure he was safe and died in the process. Periander erected a monument to the dolphin on the beach and when the ship returned with the thieving sailors he had them crucified on the beach. Equuleus is simply the "little horse" and has no mythological connections.
Stars - Gamma delphini is a nice telescopic double star with coloured components, described as yellow and emerald green. Keep an eye on this constellation, which despite its small size has played host to more than its fair share of novæ, the most famous being George Alcock’s 1967 discovery of HR delphini.
Visibility - Both of these constellations are best seen between July and October