details are unclear. Astronomy Khaqani Zij Al-Kashi produced a Zij entitled the Khaqani Zij, which was based on Nasir al-Din al-Tusi's earlier Zij-i Ilkhani. In his Khaqani Zij, al-Kashi thanks the  Timurid  sultan and mathematician-astronomer Ulugh Beg, who invited al-Kashi to work at his observatory (see Islamic astronomy) and his  university  (see  Madrasah) which taught Islamic theology as well as Islamic science. Al-Kashi produced sine tables