What is "al-saghani"

Abu Hamid Ahmed ibn Mohammed al-Saghani al-Asturlabi (meaning the astrolabe maker of Saghan, near Merv) was a Persian astronomer and historian of science. He flourished in Baghdad, where he died in 379-380 A.H/ 990 A.D.

An inventor and maker of instruments, he worked in Sharaf al-Dawla's observatory and, perhaps, constructed the instruments which were used there. Worked on the trisection of the angle.