Ahmad ibn Muhammad ibn KathÄ«r al-FarghÄnÄ«
Abu l - Abbas Ahmad ibn Muhammad ibn Kathir al - Farghani (Arabic أبو العباس أحمد بن محمد بن كثير الفرغاني, DMG ʿ Abbās Aḥmad Abu l - ibn Muḥammad ibn al - Katir Fargani, Latinized Alfraganus; † after 861 ) was a Persian astronomer the 9th century.
He came from Farghana in Central Asia, but lived mostly in Baghdad at the court of the Caliph al - Ma'mun. In Islamic culture, he was then under the name Hosib ( mathematician ) and Munadschim ar - Rais (main astronomer ) known in Europe by the Latinized form Alfraganus. He was an astronomer and engineer at Kalifenhof in Baghdad and later in Egypt, where he led the work on nilometer of Roda.
On behalf of his caliphs Farghani carried out a calculation of the circumference of the earth. To determine 2 ° of the circumference of the earth, he had the servants of the Caliph 224 km desert measured by hand. He was thus able to calculate the circumference of the earth with 99 % accuracy. He also led the calculations of the Almagest of Claudius Ptolemy ahead and tried to determine the diameter of the earth and the distance of the planets. Its elements of astronomy were translated into Latin.
The lunar crater Alfraganus was named after him.