Al-Battani

Al-Battani lived and worked for most of his life at Raqqa, now in Syria, producing his Kitāb az-Zīj aṣ-Ṣābi' around 900 - the earliest surviving astronomical table in the Ptolemaic tradition nearly untouched by Hindu or Sasanian influence. He refined Ptolemy's Almagest with new ideas and his own tables, and his observations of the Sun revealed the nature of annular solar eclipses while yielding precise values for Earth's obliquity, the solar year, and the precession of the equinoxes at one degree per 66 years. A Latin translation by Plato Tiburtinus between 1134 and 1138 carried his work west, where it became foundational: Christopher Clavius used his tables to reform the Julian calendar, and Tycho Brahe, Kepler, Galileo, and Halley all drew on his data. He also replaced Greek geometrical methods with sines and tangents, creating a trigonometric equation to find the qibla that held until al-Biruni improved it a century later. He died in 929, leaving calculations accurate enough to light the path to a new cosmology.