Ancient
Aristotle
Eratosthenes
Democritus
Hipparchus

Medieval
Abd Al-Rahman Al Sufi

Renaissance
Tycho Brahe
Copernicus
Galileo
Johannes Kepler

Age of Enlightenment
Giovanni Cassini
Edmond Halley
Sir William Herschel
Christian Huygens
Sir Isaac Newton

Modern
Albert Einstein
Williamina Fleming
Edwin Powell Hubble

Today
Stephen Hawking
Clyde Tombaugh