What is the connection between Ptolemy, an ancient Greek astronomer, and constellations?

Constellations originated in Babylon, one of the four ancient civilizations, and the Babylonians put forward 30 constellations around 1000 BC. The Tigris River and the Euphrates River flow into the Persian Gulf from northwest to southeast, so it is also called the "two river basin" area.

After the culture of the two river basins spread to ancient Greece, it promoted the cultural development of ancient Greece. Ancient Greek astronomers supplemented and developed the Babylonian constellation and compiled the ancient Greek constellation table. In the 2nd century A.D., Ptolemy, an ancient Greek astronomer, synthesized the astronomical achievements at that time and sorted out 48 constellations.

After the Middle Ages, capitalism rose in Europe, and navigation got great development. Ships sailing at sea need navigation at any time, and stars are the best street lamps. Among the stars, this constellation has a special shape and is the easiest to observe. Therefore, constellations have aroused widespread concern. When Magellan sailed around the world in the16th century, he not only used constellations to navigate and orient, but also studied constellations.

1922, the General Assembly of the International Astronomical Union decided to divide the sky into 88 constellations, and their names basically followed the historical names. 1928, the international astronomical union officially announced the names of 88 constellations. These 88 constellations are divided into three celestial regions, 29 in the northern hemisphere and 47 in the southern hemisphere, near the ecliptic 12. And the constellation we usually say is the 12 constellation on the ecliptic.