 There are two types of astronomical sextants, mural instruments and frame-based instruments.The first known mural sextant was constructed in Ray, Iran, by Abu-Mahmud al-Khujandi in 994.To measure the obliquity of the ecliptic, al-Khujandī invented a device that he called al-Fakhri sextant (al-suds al Fakhrī), a reference to his patron, Buwayhid ruler, Fakhr al Dawla (976–997).