Did Babylonian astronomers read the sky as omens or as science?

They did both, and the mix is what makes it so interesting. Babylonian astronomers watched the sky because they believed the gods used it to send messages. It was a common Mesopotamian belief that the gods indicated future events through omens, most often readable in the sky. Yet by watching carefully for centuries, they created what has been called the first successful attempt at a refined mathematical description of astronomical phenomena.

The omens came with a catch: they were avoidable. Omens from the planets were seen as more powerful, because they happened without any human action. But the events they foretold could be avoided. Eclipses were seen as the most dangerous kind. A major series of 68 or 70 tablets, Enuma Anu Enlil, collected an estimated 6,500 to 7,000 omens that interpret the sky in terms relevant to the king and state. It was the main source for the regular reports scholars sent to the Assyrian king, and well over 500 of those reports have been published. One omen reads: "If the moon at its appearance wears a crown: the king will reach the highest rank."

Now the science. The Babylonians were the first civilization known to possess a functional theory of the planets. The oldest surviving planetary text is the Venus tablet of Ammisaduqa, a 7th-century BC copy of a list of Venus observations that probably dates as far back as the second millennium BC. Using base 60, they also divided the 360-degree sky into 30-degree sections and assigned 12 zodiacal signs to the stars along the Sun's yearly path. And an ivory prism found in Nineveh, first thought to be a game, was later deciphered as a unit converter for calculating the movement of celestial bodies.

The records mattered most. Systematic astronomical diaries allowed the observation of a repeating 18-year Saros cycle of lunar eclipses. Only fragments survive, but they show that later scientific astronomy in the Greek world, India, Islam and the West depends on the Babylonian kind in fundamental ways.