This summary of the Almagest was begun by Georg Peurbach in 1460 or 1461 at the request of Cardinal Bessarion, who sought to replace George of Trebizond’s deficient translation and commentary (C.1.19). But Peurbach died unexpectedly in April 1461, as he was half-way through, and the work was continued by his student and associate Johannes Regiomontanus (1436-1476), who completed it in 1461 or 1462. Besides the Almagest, based on Gerard of Cremona’s translation (A.1.2), Peurbach and Regiomontanus made extensive use of Geber’s Liber super Almagesti (C.1.2), the Almagesti minor (C.1.4) and Albategni’s [al-Battānī] De scientia astrorum. For further works by Regiomontanus on the Almagest, see C.1.22, C.1.23. The Epitome Almagesti was used by the anonymous author of the Liber Almagesti Ptholomei abbreviatus (C.1.24).

Text ‘(Venice, BNM, Fondo antico lat. Z. 328) (1r-2r) [preface] Admiranti michi saepenumero vel potius graviter et inique ferenti tam raros esse etate nostra optimarum disciplinarum — et sic reliqua, nisi nos opinio fallit, facile superabunt. (2v-12r) [book i] Epitoma primi libri Ptolemaei. Recte profecto meo iudicio nobiliores philosophi, o Syre, distinxerunt inter theoricam philosophie et practicam partem — Patet igitur veritas corolarii atque usus eius. Finis primi. (12r-20v) [book ii] Incipit secundus. In orizonte obliquo latitudinem ortus dati puncti ecliptice per arcum semidiurnum — scilicet angulus AHT, notus fiet, qui querebatur. Finis secundi. (21r-31r) [book iii] Tercius incipit. Ingressum Solis in punctum equinoctii instrumenti adiutorio colligere — et a differentibus minuenda ut tempus mediocre proveniat. Finis tercii. (31v-38v) [book iv] Quartus incipit. Verum locum Lune in ecliptica certius per eclipses lunares quam instrumenta — inter centrum mundi et centrum epicicli reperiret. Finis quarti. (39r-50r) [book v] Quintus incipit. Instrumentum armillarum componere. Due armille decentis et eiusdem magnitudinis superficierum — qua omnia cum precisione possent inveniri. Finis quinti. (50v-61r) [book vi] Sextus incipit. Quo pacto tempus et locus medie coniunctionis luminarium reperiatur — quare arcus OH notus, qui querebatur. Finis sexti. (61v-66r) [book vii] Septimus incipit. Quod stele fixe zodiaci non modo inter se verum etiam ad eas que extra zodiacum sunt stellas distantiam — versus alterum removeantur polorum cognitas fieri necesse est. Finis septimi. (66v-72v) [book viii] Octavus incipit. Viam Lacteam per stellas quae in ea sunt notabiliores describere — accipias angulum occidentalem orizonte et ecliptica comprehensum. Finis octavi. (73r-82v) [book ix] Nonus incipit. Spherae celestes quo ordine habende sint ostendere — si que excreverint, revolucionibus habebis radicem cupitam. Finis noni. (83r-91v) [book x] Decimus incipit. Diameter ecentrici Veneris per longitudinem longiorem eius atque propiorem transiens — satis erit pro medio motu planete in longitudine radicem statuisse. Finis decimi. (92r-100r) [book xi] Undecimus incipit. Ad occasiones diversi motus Iovis quibusdam preambulis pervenire — Hec de angulis diversitatum breviter perstringere libuit. Finis undecimi. (100v-105r) [book xii] Duodecimus incipit. Si planetis altioribus unicam posueris diversitatem, epiciclus in concentrico aut ecentricus — Geminis nisibus pertingere non tua te deterreat socordia. Finis duodecimi. (105v-117r) [book xiii] Terciusdecimus. Latitudinibus trium superiorum viam speculationis aperire — quod postremo hoc in theoreumate explorare et coepto labori modum statuere decrevimus. Finis terciidecimi.’

Bibl. J.-B.-J. Delambre, Histoire de l’astronomie du Moyen Age, Paris, 1819, 284-288; E. Rosen, ‘Regiomontanus’ Breviarium’, Medievalia et Humanistica 15 (1963), 95-96; N. M. Swerdlow, ‘The Derivation and First Draft of Copernicus’s Planetary Theory: A Translation of the Commentariolus with Commentary’, Proceedings of the American Philosophical Society 117 (1973), 423-512: 425-426; N. W. Swerdlow, O. Neugebauer, Mathematical Astronomy in Copernicus’s De revolutionibus, New York, 1984, I, 50-52; E. Zinner, Regiomontanus: His Life and Work, Amsterdam-New York-Oxford-Tokyo, 1990 (tr. with additions of Leben und Wirken des Joh. Müller von Königsberg, genannt Regiomontanus, Osnabrück, 1968), 51-55 and 213-214; A. Rigo, ‘Bessarione, Giovanni, Regiomontano e i loro studi su Tolomeo a Venezia e Roma (1462-1464)’, Studi Veneziani, N. S. 21 (1991), 49-110: 77-92; A. Rigo, ‘Gli interessi astronomici del cardinal Bessarione’, in Bessarione e l’Umanesimo. Catalogo della mostra, eds G. Fiaccadori, A. Cuna, A. Gatti, S. Ricci, Napoli, 1994, 105-117: 109-113; M. Shank, ‘Regiomontanus and Homocentric Astronomy’, Journal for the History of Astronomy 29 (1998), 157-166; M. Shank, ‘Regiomontanus on Ptolemy, Physical Orbs, and Astronomical Fictionalism: Goldsteinian Themes in the “Defense of Theon against George of Trebizond”’, Perspectives on Science 10 (2002), 179-207; J. S. Byrne, The Stars, the Moon, and the Shadowed Earth: Viennese Astronomy in the Fifteenth Century, PhD dissertation, Princeton University, 2007, 156-167; M. Shank, ‘Regiomontanus as a Physical Astronomer: Samplings from The Defence of Theon against George of Trebizond’, Journal for the History of Astronomy 38 (2007), 325-349; M. Malpangotto, Regiomontano e il rinnovamento del sapere matematico e astronomico nel Quattrocento, Bari, 2008, 33-36; H. Zepeda, The Medieval Latin Transmission of the Menelaus Theorem, PhD dissertation, University of Oklahoma at Norman, 2013, 334-339; M. Shank, ‘Regiomontanus and Astronomical Controversy in the Background of Copernicus’ in Before Copernicus. The Culture and Contexts of Scientific Learning in the Fifteenth Century, eds R. Feldhay, F. J. Ragep, Montreal-London-Chicago, 2017, 79-109: 87-92; M. Shank, ‘The Almagest, Politics, and Apocalypticism in the Conflict between George of Trebizond and Cardinal Bessarion’, Almagest 8 (2017), 49-83: 56-57; H. Zepeda, The First Latin Treatise on Ptolemy’s Astronomy: The Almagesti minor (c. 1200), Turnhout, 2018, 109-114; M. Shank, ‘Regiomontanus versus George of Trebizond on Planetary Order, Distances, and Orbs (Almagest 9.1)’, in Ptolemy’s Science of the Stars in the Middle Ages, eds D. Juste, B. van Dalen, D. N. Hasse, C. Burnett, Turnhout, 2020, 305-386; M. Malpangotto, Theoricae novae planetarum Georgii Peurbacii dans l’histoire de l’astronomie, Paris, 2021, 33-34 and 38.

Modern ed. None, but there is a facsimile of ed. Venice 1496 in F. Schmeidler, Joannis Regiomontani opera collectanea. Faksimiledrucke von neun Schriften Regiomontans und einer von ihm gedruckten Schrift seines Lehrers Purbach, Osnabrück, 1972, 55-274.