“Cassiopeia was the wife of Cepheus, the Ethiopian king of Joppa (now known as Jaffa, in Israel), and the mother of Andromeda. The queen was both beautiful and vain, and the story of how her vanity caused great distress is told in relation to the constellation Andromeda. After promising her daughter in marriage to Perseus, Cassiopeia had second thoughts. She convinced one of Poseidon’s sons, Agenor, to disrupt the ceremony by claiming Andromeda for himself. Agenor arrived with an entire army, and a fierce struggle ensued.
In the battle Cassiopeia is said to have cried “Perseus must die”. At any rate it was Perseus who was victorious, with the help of the Gorgon’s head. Perseus had recently slain Medusa, the Gorgon, and had put its head in a bed of coral. He retrieved the head and waved it in midst of the warring wedding party, instantly turning them all to stone. In the group was both Cepheus and Cassiopeia.
A contrite Poseidon put both father and mother in the heavens. But because of Cassiopeia’s vanity, he placed her in a chair which revolves around the Pole Star, so half the time she’s obliged to sit upside down. ”