in general, as exemplified in the works of Ibn al-Shatir, al-Qushji, al-Birjandi and al-Khafri. [92] [93] [94] Ibn al-Shatir ‘s model for the appearances of Mercury , showing the multiplication of epicycles using the Tusi-couple , thus eliminating the Ptolemaic eccentrics and equant . Other achievements of the Maragha school include