Why Muslim Scientific Discovery Slow To a Trickle After Roughly 950 AD?
… corrections like orbits within orbits, known as epicycles, and geometrical modifications.
Al-Tusi found a way to restore most of the symmetry to Ptolemy’s model by adding pairs of cleverly designed epicycles to each orbit. Following in al-Tusi’s footsteps, the 14th-century astronomer Ala al-Din Abul-Hasan ibn al-Shatir had managed to go further and construct a completely symmetrical model. – New York Times
Other accounts contradict this, that Islamic discoveries had stopped by the end of the 12th century. But they greatly slowed after 950 AD. This means the Islamic Golden Age was closer to …