The current list of constellations recognised by the International Astronomical Union is based on those listed by Claudius Ptolemy, Greek-speaking mathematician, geographer, astronomer, and astrologer who lived in the Hellenistic culture of Roman Egypt. He may have been a Hellenized Egyptian, but he was probably of Greek ancestry, although no description of his family background or physical appearance exists, though it is likely he was born in Egypt, probably in or near Alexandria.

Greek astronomy was built on Mesopotamian foundations. They defined the Zodiac and at least another 18 constellations taken over or adapted by the Greeks:

The earliest direct evidence for the constellations comes from inscribed stones and clay writing tablets dug up in Mesopotamia (within modern Iraq)... It appears that the bulk of the Mesopotamian constellations were created within a relatively short interval from around 1300 to 1000 B.C...

The Mesopotamian groupings turn up in many of the classical Greek constellations. The stars of the Greek Capricorn and Gemini, for example, were known to the Assyrians by similar names - the Goat-Fish and the Great Twins. A total of 20 constellations are straight copies. Another 10 have the same stars but different names. The Assyrian Hired Man and the Swallow, for instance, were renamed Aries and Pisces.

In more recent times, Ptolemy's list has been added to in order to fill gaps between Ptolemy's patterns. The Greeks considered the sky as including both constellations and dim spaces between. But Renaissance star catalogs by Johann Bayer and John Flamsteed required every star to be in a constellation, and the number of visible stars in a constellation to be manageably small.

The constellations around the South Pole were not observable by the Greeks. Twelve were created by Dutch navigators Pieter Dirkszoon Keyser and Frederick de Houtman in the sixteenth century and first cataloged by Johann Bayer. Several more were created by Nicolas Louis de Lacaille in his posthumous Coelum Australe Stelliferum, published in 1763.

Other proposed constellations didn't make the cut, most notably Quadrans Muralis (now part of Boötes) for which the Quadrantid meteors are named. Also the ancient constellation Argo Navis was so big that it was broken up into several different constellations, for the convenience of stellar cartographers.

Source : www.wikipedia.org