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.
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