Life
Al-Battani (c. 858–929) conducted decades of careful astronomical observation, refining the value of the solar year, the precession of the equinoxes, and the orbits of the sun and moon, and introducing key trigonometric methods and functions. His tables and treatise, translated into Latin, influenced European astronomers including Copernicus, who cited him. He is regarded as one of the greatest astronomers of the medieval world.