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 as the basis for computations. Since most
zījes generally followed earlier theory, their principal contributions reflected improved trigonometrical, computational and observational techniques. The content of
zījes were initially based on that of the "Handy Tables" by
Ptolemy, known in Arabic as
al-Qānūn, the
Zīj-i Shāh compiled in Sasanian Persia, and the Indian
siddhantas by
Āryabhaṭa and
Brahmagupta. Muslim
zījes, however, were more extensive, and typically included materials on
chronology, geographical
latitudes and
longitudes,
star tables,
trigonometrical functions, functions in
spherical astronomy, the
equation of time, planetary motions, computation of
eclipses, tables for first visibility of the
lunar crescent, astronomical and/or
astrological computations, and instructions for astronomical calculations using
epicyclic geocentric models. Over 200 different
zījes have been identified that were produced by
Islamic astronomers during the period from the eighth to the fifteenth centuries. The greatest centers of production of
zījes were
Baghdad under the
Abbasid caliphs in the ninth century, One of the most famous Indian
zījes was the
Zīj-i Muhammad Shāhī, compiled at
Sawai Jai Singh's
Jantar Mantar observatories in the
Kingdom of Amber. It is notable for employing the use of
telescopic observations. The last known
zīj treatise was the
Zīj-i Bahadurkhani, written in 1838 by the Indian astronomer Ghulam Hussain Jaunpuri (1760–1862) and printed in 1855, dedicated to
Bahadur Khan. The treatise incorporated the
heliocentric system into the
zīj tradition. ==List==