From time immemorial, humans have imagined the stars in the form of any animals or humans, divided them into groups and added interesting stories. Using the constellations made it easier to find the stars and remember their positions. Therefore people used constellations to navigate while sailing or having a long journey using constellations as a map. That’s why people called constellations a map of the night sky or a storybook of the sky. These storybooks of the sky have interesting stories behind related to greek mythology. Here are 3 constellations that have interesting myths beyond.
Perseus
In Greek mythology, Perseus was the son of Danaë, who sent by king Polydectes to bring the head of Medusa. Medusa has winged human females with living venomous snakes in place of hair. Those who gazed into her eyes would turned to stone. Perseus rescued Andromeda from the monster by killing it with his sword. When Perseus proved his mission success by showing Polydectes the Medusa’s head, Polydectes and his wedding guests all turned to stone. Perseus gave to Medusa’s head to Athena, who attached in to the front of her shield. 
Perseus lived to a great old age and became the king of Mycenae, and married Andromeda. After his death, Zeus gave Perseus a place among the constellations next to his beloved Andromeda.
Aries
Athamas, the king of Thessaly, and his remarried wife Ino had two children named, Phrixus and Helle. Unfortunately, Ino treated her children very badly. Hermes saw kids treated cruelly by their stepmother and sent a magical ram, Aries, to help children escape their stepmother’s wrath. Children flew over land and sea to the east. Unfortunately, Helle failed to get a good hold on ran’s fleece. She fell off and drowned. Phrixus landed safely on the edge of the Black Sea, Colches. 
In gratitude for his safe deliverance, Phyrixus sacrificed the ram and gave its golden fleece to the king of that country. Zeus placed the ram’s constellation, Aries, who had great sacrifice in saving the children in the night sky.
Orion
Orion was a great skilled hunter, and he provided meat each day for the gods. One day the moon goddess, Artemis, asked to hunt together with him. On their hunt, Orion shot deer with his arrow perfectly and pleased Artemis. At dinner, Artemis told everyone including Zeus, about Orion’s great skills with the bow. All of them praised and pleased Orion, and he vowed to impress Artemis, even more.
The next day, Orion shot every animal he found. He put a large pile of dead animals to Artenis’ house. Then, he shows Artemis the dead animals to impress her. Artemis was horrified. She is the protector of animals and punished those who killed more than they could eat. Artemis stomped her foot on the ground, and a great scorpion appeared. It stung Orion, causing him to die in great pain. However, in honour of his great service to the gods, Zeus placed his constellation in the sky.
You can find out more interesting stories beyond the constellation from these sites:
http://www.tcoe.org/scicon/instructionalguide/constellations.pdf
https://www.windows2universe.org/mythology/const_nav.html