This was considered a science in ancient days. Schools of learning were built just to interpret the celestial bodies amongst the stars. It was believed that these signs were communications from the heavens. It was mainly a priest class that would keep a record of this information for themselves or to warn the people of upcoming events.
Astrological readings were about large-scale events. This could be war, famine, or the death of a ruler. It was said that an astrological reading by the Aztecs predicted the coming of the Spanish. The Aztecs knew they would bring death but were still complacent. They thought they were dealing with human beings like themselves.
Some astrologers calculated where the celestial bodies would be in the past at the time of great events. They would then calculate when the same pattern would happen again. This could predict a specific type of event reoccurring sometime in the future. They understood that human behaviour is stuck in a continuous repeat cycle.
It is said that astrology is still used by those who run this world. This is to calculate the success of any events that are to take place. It is one of the reasons why occult symbols and numeracy are used. The events can have a positive or negative affect on the populace at once. Astrology is a worthwhile endeavour for the exoteric type.
There are people who use Horoscopes, but these are incredibly inaccurate and are based on wishful thinking. If they told the truth, nobody would read them. Mainstream Tarot readings are the same. It is always best to learn occult sciences to make your own interpretations or at least honest ones for others. Accuracy takes a lot of time.
There are many books on Astrology. In ancient times, astrology only used the Sun, the Moon, and those planets that could be seen in the sky. The planets, Mercury, Venus, Mars, Jupiter and Saturn. Later ones included Uranus and Neptune.
Eventually, Pluto was added. Then, when Pluto was downgraded to a dwarf planet, rather than disregard it, other dwarf planets were added. It has become bizarre. It is best to stick to the original Astrology as ancient charts can be used for accuracy or verification.