The book contains tables for calculating the positions of the planets and the names of the stars. It included data derived from the observations of the stars and planets over 12 years in the Maragha observatory, completed in 1272. The planetary system of Tusi was the most advanced of his period and was used extensively until the development of the heliocentric model in the time of Copernicus.
The book also describes a method of interpolation between the observed positions, which in modern terms may be described as a second-order interpolation scheme.
History
Hulagu Khan believed that many his military successes were due to the advice of astronomers (who were also astrologers), especially of al-Tusi. Therefore when al-Tusi complained that his astromical tables were 250 years old, Hulagu gave permission to build a new observatory in a place of al-Tusi's choice (he chose Maragheh). A number of other prominent astronomers worked with al-Tusi there, such as Muhyi al-Din al-Maghribi, Mu'ayyid al-Din al-'Urdi, from Damascus, Qutb al-Din al-Shirazi, and Hulagu's Chinese astronomer Fao Munji whose Chinese astronomical experience brought improvements to Ptolemaic system used by al-Tusi - traces of the Chinese system may be seen in Zij-i Ilkhani. The tables were published during the reign of Abaqa Khan, Hulagu's son, and named after the patron of the observatory. They were popular until the 15th century.
