Pseudo-Masha’allah, On the Astrolabe

A Critical Edition of the Latin Text with English Translation by Ron B. Thomson

Guest post by Ron B. Thomson
Pontifical Institute of Mediaeval Studies, Toronto
2/9/2015: Updated files have now been published at

The astrolabe was the most important scientific instrument in the Middle Ages, and the treatise ascribed to Masha’allah (ca 800 C.E., 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 100 copies of each part of the treatise.

The 1935 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-copies or mis-read phrases at times makes that text unintelligible.

This edition is based on the collation of a significant number of manuscripts (over 80, and eventually, it is hoped, all manuscript copies). What is now being published here is the text of the Prologue and of the first 16 chapters (version 1.1). The edition is available in the ShareOK repository.

Over time these texts will be updated and expanded, when the remaining manuscript copies are collated, and when the editing of further sections has been completed. However, it is not expected that the present version will change – the rest of the manuscripts will expand the apparatus criticus but are unlikely to modify the text itself.

The proper citation of this work is: Pseudo-Masha’allah, On the Astrolabe, ed. Ron B. Thomson, version 1.1 (Toronto, 2012, 2015), accessed at

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

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.

Note: We thank Prof. Thomson for this guest post, and for making this important edition available to scholars in electronic form as downloadable pdfs from Bookmark this page to obtain future versions of Prof. Thomson’s edition. Should it become available elsewhere, this page will forward visitors to the most current location.

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