Jamshid al-Kashi

Ghiyath al-Din Jamshid Mas'ud al-Kashi, known as Jamshid al-Kashi, was an astronomer and mathematician born about 1380 in Kashan, Iran, who died in Samarkand on 22 June 1429. He observed a lunar eclipse at Kashan in 1406 and wrote astronomical works including The Stairway of Heaven, on determining the distances and sizes of the heavenly bodies, and the Khaqani Zij, a book of astronomical tables dedicated to Ulugh Beg. Those tables gave sine values, transformations between ecliptic and equatorial coordinates on the celestial sphere, and detailed tables of the motion of the sun, moon and planets, along with tables of parallax, eclipses and lunar visibility. He worked at the court and school of Ulugh Beg in Samarkand, where an observatory was begun in 1424, and was regarded by a later historian as a second Ptolemy. He also calculated pi to sixteen decimal places and used decimal fractions in his Key to Arithmetic.