Alfonsine Astronomy: Computational Practices

Matthieu Husson, José Chabás, Richard Kremer (eds)

Pages: 546 p.
Size:178 x 254 mm
Illustrations:38 b/w, 44 col., 27 tables b/w.

Language(s):English, Latin
Publication Year:2026

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Unfolding more than two centuries of late mediaeval astronomers’ computational practices, this collective volume explores new venues in the history of astronomy.

Subject(s)

BIO

Matthieu Husson researches the history of late medieval astronomy in Europe and was the PI of the ERC project ALFA based in the Observatoire de Paris‑PSL.

José Chabás † was emeritus professor at Universitat Pompeu Fabra and authored several monographs on the history of astronomy.

Richard L. Kremer is emeritus professor of history at Dartmouth College and associate and reviews editor of the Journal for the History of Astronomy.

Summary

From the late thirteenth century, when Alfonsine astronomy began to take shape under Alfonso X’s patronage in Castille, to the first decades of the sixteenth century, when Alfonsine astronomy had become a common computational tool throughout Europe, astronomers compiled works on tables, instruments, procedures, and theory—now preserved in more than 900 manuscripts from the fourteenth and fifteenth centuries. These sources reveal that Alfonsine astronomers focused on elaborating procedures rather than theoretical speculations or celestial observations. Their procedures—expressed through texts, tables, diagrams, and instruments—were designed to compute astronomical positions.

This volume explores computational practices across four sections: (1) procedural texts related to table sets and instruments; (2) tables and table sets, their geometrical and theoretical grounding, purposes, and numerical derivation; (3) questions of numbers, accuracy, rounding, and interpolation; and (4) ephemerides and horoscopes as boundary genres between mathematical astronomy and wider audiences.

TABLE OF CONTENTS

Introduction
Matthieu Husson, José Chabás, and Richard Kremer

Part 1: Procedural Texts

A Note on Arabes Maxime
Eleonora Andriani, Nicholas Jacobson and Samuel Gessner

Conrad Heingarter’s Treatise on Planetary Latitude
Eleonora Andriani, Camille Bui and Nicholas Jacobson

The Planicelium of John Vimond
Samuel Gessner and Marie-Madeleine Saby

Exempla in figura in Alfonsine Canon Commentaries
Nicholas Jacobson

Part 2: Reconfiguring Tables

Mathematical Treatment of Alfonsine Trepidation
Petr Hadrava

Emergence of Auxiliary Astronomical Tables in Europe
Glen Van Brummelen

Computing Solar and Lunar Velocities and Radii
José Chabás and Bernard R. Goldstein

Trigonometric Tables of Jean Fusoris
Jean-Claude Penin

Regiomontanus on the Equation of Time
Eleonora Andriani and Stefan Zieme

Part 3: Operating with Numbers

Cyclical Radices in the Tabule resolute
Alena Hadravová and Petr Hadrava

Computational Practices in Alfonsine Astronomy
José Chabás

Proportional Parts and Interpolation Practices
Matthieu Husson

Part 4: On the Border of Mathematical Astronomy

Medieval Ephemerides
Richard L. Kremer

Astronomical Computation to Astrological Interpretation
Alexandre Tur