Risala fi da'irat al-mu'addil (al-Wafa'i)

Risala fi da'irat al-mu'addil (al-Azhar Library no. 533/88225) by Abd al-Aziz al-Wafa'i concerns an instrument he devised in the fifteenth century, which according to the book astronomers class as a multi-purpose instrument; its name literally means "the equatorial circle". ^{1 2}

It consists of a semicircular frame fixed at the ends of its diameter to a horizontal base, which can be set parallel to the celestial equator at any latitude, with a sighting device mounted radially on the frame, so that the hour-angle of any body whose declination is less than the obliquity of the ecliptic can be measured; the base carries lines giving the qibla for different places. ² It attracted commentaries, among them al-Mufassal fi da'irat al-mu'addil by Abu al-Fath al-Sufi al-Misri. ² The Azhar copy, from the "Turkish gifts" collection, has five folios. ²