Azij (Persian:زيج,romanized: zīj) is anIslamic astronomical book that tabulatesparameters used forastronomical calculations of thepositions of the sun, moon, stars, and planets.
The namezīj is derived from theMiddle Persian termzih orzīg "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 asqānūn, derived from the equivalent Greek word,κανών.[1]
TheZij-i Sultani, published by the astronomer andsultanUlugh Beg in 1438/9, was used as a referencezij throughout Islam during theearly modern era.[2]Omar Khayyam'sZij-i Malik Shahi was updated throughout the modern era under various sultanates.[2]Zijes were updated by different empires to suit their various interests, such as the simplified version ofZij-i Sultani by theMughal Empire.[2]
Some of the earlyzījes tabulated data fromIndian planetary theory (known as the Sindhind) and from pre-IslamicSasanian models, but mostzījes presented data based on thePtolemaic model. A small number of thezījes adopted their computations reflecting original observations but most only adopted their tables to reflect the use of a different calendar or geographic longitude as the basis for computations. Since mostzījes generally followed earlier theory, their principal contributions reflected improved trigonometrical, computational and observational techniques.[1][3]
The content ofzījes were initially based on that of the "Handy Tables" byPtolemy, known in Arabic asal-Qānūn, theZīj-i Shāh compiled in Sasanian Persia, and the Indiansiddhantas byĀryabhaṭa andBrahmagupta. Muslimzījes, however, were more extensive, and typically included materials onchronology, geographicallatitudes andlongitudes,star tables,trigonometrical functions, functions inspherical astronomy, theequation of time, planetary motions, computation ofeclipses, tables for first visibility of thelunar crescent, astronomical and/orastrological computations, and instructions for astronomical calculations usingepicyclicgeocentric models.[1] Somezījes go beyond this traditional content to explain or prove the theory or report the observations from which the tables were computed.[1] Due to religious conflicts with astrology, many astronomers attempted to separate themselves from astrology, specifically intending for theirzījes not to be used for astrological computations. However, manyzījes were used this way regardless, such asibn al-Shatir'sal-Zij al-jadīd.[4]
Over 200 differentzījes have been identified that were produced byIslamic astronomers during the period from the eighth to the fifteenth centuries. The greatest centers of production ofzījes wereBaghdad under theAbbasid caliphs in the ninth century,[1] theMaragheh observatory in the 13th century, theSamarkand observatory in the 15th century, and theConstantinople observatory of Taqi ad-Din in the 16th century. Nearly 100 morezījes were also produced in India between the 16th and 18th centuries.[5] One of the most famous Indianzījes was theZīj-i Muhammad Shāhī, compiled atSawai Jai Singh'sJantar Mantar observatories in theKingdom of Amber. It is notable for employing the use oftelescopic observations.[6] The last knownzīj treatise was theZīj-i Bahadurkhani, written in 1838 by the Indian astronomer Ghulam Hussain Jaunpuri (1760–1862) and printed in 1855, dedicated toBahadur Khan. The treatise incorporated theheliocentric system into thezīj tradition.[7]
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