Zij
A () is an Islamic astronomical book that tabulates parameters used for astronomical calculations of the positions of the sun, moon, stars, and planets. Etymology The name zīj is derived from the Middle Persian term or "cord". The term is believed to refer to the arrangement of threads in weaving, which was transferred to the arrangement of rows and columns in tabulated data. Some such books were referred to as , derived from the equivalent Greek word, . Historically significant zījes The Zij-i Sultani, published by the astronomer and sultan Ulugh Beg in 1438/9, was used as a reference throughout Islam during the early modern era. Omar Khayyam's Zij-i Malik Shahi was updated throughout the modern era under various sultanates. were updated by different empires to suit their various interests, such as the simplified version of by the Mughal Empire. History Some of the early zījes tabulated data from Indian planetary theory (known as the Sindhind) and from pre-Islamic Sasanian models, but most zījes presented data based on the Ptolemaic model. A small number of the zījes adopted their computations reflecting original observations but most only adopted their tables to reflect the use of a different calendar or geographic longitude