Living in a world without electric lights, most ancient people were much more familiar with the night sky than we are, and the stars and planets were very important to their view of the universe.Many believed that events in the sky were closely linked to events on earth; a belief that developed into the pseudo-science of astrology. In Sumerian cuneiform writing, a star and crescent is theideogram for "incantation" or magical spell.

At least four different Greco-Roman goddesses had a lunar connection: Hecate, Selene, Artemis (Diana), and Aphrodite (Venus). The star and crescent appears as a powerful symbol with many meanings,and it is often found on ancient coins.

Uranopolis and Byzantium
The small town of Uranopolis ("sky city") in Macedon was dedicated to the sky goddess Aprhrodite Urania. On its bronze coins (c. 300 BCE), the goddess appears seated on a celestial globe. The starand crescent are depicted on the reverse, in a pattern that will be repeated on coins for centuries to come: the "horns" of the crescent point upward, and the star is a pellet with six or eightrays.

The Greek city of Byzantium (which would become Constantinople in 330 CE, and, Istanbul after 1453) adopted this symbol on its coinage in the first century BCE. According to legend, in 340 BCE,when Philip of Macedon (father of Alexander the Great) besieged Byzantium, the appearance of a sudden light in the sky warned the defenders in time to prevent a surprise night attack on the walls. Ingratitude to the lunar goddess Hecate, the city placed a star and crescent on its local coinage. This custom continued well into the Roman era.

Roman Imperial
Many Roman emperors took astrology seriously; some even employed court astrologers. Beginning with the first emperor, Augustus, the crescent symbol with one or more stars appears repeatedly on thecoinage, probably at times when significant lunar events were observed and taken as favorable omens.

To read the complete article, see:
The Star and Crescent on Ancient Coins (http://coinweek.com/ancient-coins/star-crescent-ancient-coins/)