Al-Battani's Astronomical Tables

Around 900 CE, Arab astronomer Al-Battani completed 'Kitāb az-Zīj' (Book of Astronomical Tables), which improved upon Ptolemy's astronomical calculations. Based on observations at ar-Raqqah in Syria, Al-Battani provided more accurate values for the length of the solar year, the precession of the equinoxes, and the inclination of the ecliptic. He proved the motion of the solar apogee relative to the stars, which Ptolemy had considered fixed. Al-Battani's tables and trigonometric methods were translated and used throughout Europe for centuries, influencing later astronomers including Copernicus, who cited Al-Battani's work 23 times.