Astronomy is learning about the solar system and all of the universe. Galaxies! Stars! Planets! Black Holes! Quasars! Pulsars! Planets! Moons! Asteroids! Dark matter?! The speed of light! Gravity! Gravitational lensing! Spectrometry!

Astrology is thinking that the current position of mercury is the causal reason your girlfriend cheated on you. Or that the month you were born determines your personality.