Therefore, when al-Tusi complained that his astronomical 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, including Muhyi al-Din al-Maghribi, Qutb al-Din al-Shirazi, Mu'ayyid al-Din al-'Urdi from Damascus. Furthermore, the influence of Chinese astronomy was brought by Fao Munji, whose astronomical experience brought improvements to Ptolemaic system used by al-Tusi; traces of the Chinese system may be seen in Zij-i Ilkhani.