A Guide for the Perplexed on the Drawing of the Circle of Projection


The author of this work, Ibn al-Majdī (1366-1447 [767-850 A.H.]), was a renowned mathematician, geometrician, and astronomer. He was linked with the influential Marāgha School through his teacher, Jamāl al-Dīn al-Māridīnī, who in turn had studied with Ibn al-Shātir al-Dimashqī’. As a descendant of a powerful local family with Mamlūk ties, Ibn al-Majdī served as the official astronomer and timekeeper at Al-Azhar. The work is divided into three chapters and a conclusion. Chapter 1 covers the procedure for projecting the circle of projection (fadl al-dā’ir) onto planes that run parallel to the horizon, each one of which is known as a simple plane (basīta). Chapter 2 is devoted to a discussion of planes that run perpendicular to the horizon, and which are referred to as planes of declination (munharifāt). Chapter 3 considers the same problem as the previous chapter in the case when intersecting planes are not perpendicular to the horizon. The conclusion deals with such questions as locating the North Pole and determining one’s latitude. The book offers six ways for drawing the circle of projection and provides several tables with numerical data.

Last updated: November 18, 2015