The astrolabe was the most important scientific instrument in the Middle Ages, and the treatise ascribed to Māshā’allāh (but not actually by him) is the most important text on the subject. It was much copied and survives in all or in part in almost 200 manuscripts. Generally there are more than 140 copies of each part of the treatise.

The 1929 edition published by R. T. Gunther was based on only three or four local manuscripts, and as such is defective in many places. Missing phrases, or mis-copied or mis-read phrases at times make that text unintelligible.

This edition is based on the collation of all the extant manuscripts. What is now being published here (Version 1.7) is the text of the Prologue and of the twenty-two chapters of the Compositio text, an edition of the Lists of Stars normally found with the text, and the Prologue and the forty-seven chapters of the Practica text.

The edition is available in four PDF files:

Part I: Introduction containing the preface and introductory material, including manuscript information;

Part II: a critical edition of the Compositio text – the Latin text and diagrams, the critical apparatus and a facing English translation;

Part III: Lists of Stars, edited and translated, with an appendix containing information about all the stars mentioned in the text and tables;

Part IV: A critical edition and translation of the Practica text, or how to use an astrolabe.

The editor is interested in the receiving comments on the text, and further insights into its interpretation, from others. He is willing to incorporate such additions into later versions for the benefit of those who would consult this edition in the future. Comments can be sent to thomson@chass.utoronto.ca.

Permission is given for scholars to print out (and bind) any or all of these texts for non-commercial uses: research, study, criticism and citation. Commercial reproduction of all or part of the texts is not permitted without the prior consent of the copyright owner.

This is the latest version of the work. Previous versions are available at https://shareok.org/handle/11244/14221 and https://shareok.org/handle/11244/14221.2