Astrology?
That’s an interesting question.
In reality, our ancient cultures saw a sky (that we’ll never see again) full of stars and found pictures in them - they placed in the sky their gods, heroes, animals. In most places the changing night sky began to determine important agricultural dates. That relation to time easily led to associating the time of one’s birth with ascendant celestial objects.
That’s what happened here.
Imagine, instead, a magical world, where our Babylonian, Grecian, or Mayan sages knew for a fact that stars expresses some sentience we only barely understand; that a multitude of very real monsters came travelling from those stars. Their own Sun, an expression of Law and Good, but only by virtue of it’s ownership of our planet - each other star’s Law inimical to our survival.
On top of that, their cultures are ascendant only by long, bloody struggle, against millennia of crushing oppression from alien invaders; first in the form of the Snakemen, second in form of the First Men and Half-Elven Princes, the last’s yoke only thrown of by virtue of them become bored with rulership.
That is what the stars and planets bring them - horrors, oppression, knowledge that only leads to ruin. They learn to harness the force of Law from the Sun in defense of civilization, against those who learn darker secrets from further stars.
Would people in that world look up at a clear night sky with a sense of wonder or dread? Would they connect their heroes to those dreadful lights? Would horoscopes from those stars be anything but a curse, or merely some silly game to scare children, like a Ouija board?
A sad world, under that baleful sky, that cannot look up and hope.
In our world, the scariest thing in the skies were the things that merely changed - comets, let’s say, whose appearance was often twisted to facilitate terrestrial plans. Or variable stars, like Algol (The Demon Star, Arabic name, just an eclipsing binary star system). In this modern age if we suddenly had proof that alien life not only existed but could contact and occasionally visit us, the near-space of Earth would be weaponized in the blink of an eye.
So - TL;DR - astrology. Probably, in certain forms. But I’d bet it’d be an underground sort of thing; a practice of cults and dark magics; an astrological arithmetic meant less to predict first loves and more to facilitate communing with minds beyond.
