Battani, abu-'Abdullah Muhammad ibn-Jabir al-(also Albategni, Albategnius, Albatenius)

Al-Battani was an Arab astronomer/astrologer and mathematician.

850 - Al-Battani was born in Harran near Urfa, which is now in Turkey.

His best-known achievement was the determination of the solar year as being 365 days, 5 hours, 46 minutes and 24 seconds.

Calculated the values for the precession of the equinoxes (54.5" per year, or 1° in 66 years) and the inclination of Earth's axis (23° 35').

Used a uniform rate for precession in his tables, choosing not to adopt the theory of trepidation attributed to his colleague Thabit ibn Qurra.

923 - Al-Battani died in Syria.

The Albategnius crater on the Moon was named after him.