Al-Farghoniy

      Ahmad ibn Mohamad ibn Kathir Al-Farghaniy, born in Farghana, was one of the most distinguished astronomers in the service of Khalif al-Mamun and his successors. He wrote "Elements of Astronomy" (Kitab fi al-Harakat al-Samo wa Jawami Eilm al-Nujum i.e. the book on celestial motion and thorough science of the stars), which was translated into Latin in the 12th century and exerted great influence upon European astronomy before Regiomontanus. He accepted Ptolemy's theory and value of the precession, but thought that it affected not only the stars but also the planets. He determined the diameter of the earth to be 6,500 miles, and found the greatest distances and also the diameters of the planets.

       Al-Farghaniy's activities extended to engineering. According to Ibn To'ri Birdi, he supervised the construction of the Great Nilometer at Al-Fustat (old Cairo). It was completed in 861, the year in which the Caliph Al-Mutawakkil, who ordered the construction, died.

     The "Fihrist" of Ibn al-Nadim, written in 987, ascribes only two works to al-Farghani: (1) "The Book of Chapters, a summary of the "Almagest" (Kitab al-Fusul wa Ikhtiyar al-Majisti ) and (2) "Book on the Construction of Sun-dials" (Kitab 'Amal al-Rahamat).

   'The Elements' was Al- Farghanyi's best-known and most influential work. Abdulaziz al-Qabisi wrote a commentary on it, which is preserved in the Istanbul manuscrip. Two Latin translations followed in the 12th century. Jacob Anatoli produced a Hebrew translation of the book that served as a basis for a third Latin version, appearing in 1590, whereas Jacob Golius published a new Latin text together with the Arabic original in 1669. The influence of 'The Elements' on medieval Europe is clearly vindicated by the presence of innumerable Latin manuscripts in European libraries.

     References to it by medieval writers are many, and there is no doubt that it was greatly responsible for spreading knowledge of Ptolemaic astronomy, at least until this role was taken over by Sacrobosco's Sphere. But even then, 'The Elements' of Al-Farghaniy continued to be used, and Sacrobosco's Sphere was evidently indebted to it. It was from 'The Elements' (in Gherard's translation) that Dante derived the astronomical knowledge displayed in the 'Vita nuova' and in the 'Convivio'.