ABSTRACT
The Latin treatise on the construction 1 and use 2 of the astrolabe circulating undei the name of Messahalla (═ Māšā'allāh)3 can be regarded as the most popular and widespread treatise on the subject in the middle ages. The number of manu-scripts in which this text has survived amounts to almost 2004. It was repeatedly printed5, and its fame was still more increased since Chaucer took Messahalla's work as a basis for the elaboration of his own treatise on the astrolabe, in English. In spite of its historical importance, no critical edition of the text has previously been made. The best available, though not fully reliable, is at present that made by R. T. Gunther in 19296. Gunther's version was used by Mlllas in 1931, and we shall take it as a basis of our present study7.
