Qushji improved on Nasir al-Din al-Tusi 's planetary model and presented an alternative planetary model for Mercury. He was also one of the astronomers that were part of Ulugh Beg 's team of researchers working at the Samarqand observatory and contributed towards the Zij-i-Sultani compiled there. In addition to his contributions to Zij, Ali Kuşçu wrote nine works in astronomy, two of them in Persian and seven in Arabic. A Latin translation of two of Qushji's works, the Tract on Arithmetic and Tract on Astronomy, was published by John Greaves in 1650.