Astrolabe of 'Umar ibn Yusuf ibn 'Umar ibn 'Ali ibn Rasul al-Muzaffari. Dimensions: Case (a): Max. W. 7 5/8 in. (19.4 cm) Diam. 6 1/8 in. (15.6 cm) D. 1/4 in. (0.6 cm)Bar with attached nail (b): Max. H. 1 7/8 in. (4.8 cm)Max. W. 1 1/8 in. (2.9 cm)L. 5 in. (12.7 cm)Net (c): Diam. 5 in. (12.7 cm)Plates (d-g): Diam. 5 in. (12.7 cm)Pin (h): L. 1 3/4 in. (4.4 cm)W. 1/2 in. (1.3 cm). Maker: 'Umar ibn Yusuf ibn 'Umar ibn 'Ali ibn Rasul al-Muzaffari. Date: dated A.H. 690/ A.D. 1291.For an object produced during the medieval period, this astrolabe is unusually well documented. Its inscription attributes it to a Rasulid prince, 'Umar ibn Yusuf, a few years before he ascended to the throne (r. 1295-96). 'Umar compiled a number of scientific treatises, including one on the construction of astrolabes, an autographed version of which, preserved in Cairo, contains certifications by his teachers as to his competence as a maker of such devices and a description of this very piece. Museum: Met