Studying modern astronomy requires a thorough understanding of physics and advanced mathematics.
But in ancient times, when the Greeks were seeding the science, astronomy was grounded in observing and remembering. Astronomy was recording the methodical movement and occurrences within the universe that could be seen in the sky. Much of what was noticed was tied to another budding science - agriculture.
... when the Pleiades rise it is time to use the sickle, but the plough when they are setting; 40 days they stay away from heaven; when Arcturus ascends from the sea and, rising in the evening, remain visible for the entire night, the grapes must be pruned; but when Orion and Sirius come in the middle of heaven and the rosy fingered Eos sees Arcturus, the grapes must be picked; when the Pleiades, the Hyades, and Orion are setting, then mind the plough; when the Pleiades, fleeing Orion, plunge into the dark sea, storms may be expected; 50 days after the sun's turning is the right time for man to navigate; when Orion appears, Demeter's gift has to be brought to the well-smoothed threshing floor...
The above was written by Hesiad, one of the earliest Greek poets, around 700 BC. In those days, astronomy was time keeping. It reorganized that an astronomical events such as one day was a natural period of time. Then awareness of the periodic phases of the moon creates a larger natural time span. Knowledge of this approximate, yet reliable flowing length of the year was vital for food production.
Farmers began noticing the rising and setting of constellations, then base their planting strategies on them. For many hundreds of years astronomers would write works on such rising and setting of constellations indicating that the type of advice given by Hesiad continued to be used. One of the first was a weather-calendar, called a parapegma.
It was simply a list of dates of seasonally regular weather changes, listed next to the times of appearance of various stars and constellations. The parapegma was the precursor of something we still produce and use today - almanacs. The origin of the word almanac is obscure, but it is believed to have come from the Greek word, almenikhiaka, meaning ephemeris, which is a record of planetary positions.
An almanac is an annual publication containing lots of astronomical information, including daily rising and setting times of the sun and moon, eclipses, timing of high tides, festivals and more. It is still used by farmers today.

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