Ars
Astronomica
A scholarly imprint producing first English translations of historical Hebrew and Latin works in astronomy, cosmology, and natural philosophy.
These texts span centuries, and most have never appeared in English. One – Gersonides’ 136-chapter mathematical astronomy – was never printed and survives only in manuscript. They cite and answer one another, addressing the same cosmological questions, yet until now no one could read them side by side in a single language.
The corpus
Date
Author
Work
Source
Description
Translator Version
1665
Athanasius Kircher
Mundus Subterraneus
footnotes
Internet Archive — athanasiikircher12kirc
A vast attempt to explain the whole hidden world beneath our feet.
2
c. 1613
David Gans
Nechmad ve-Na’im
footnotes
National Library of Israel — Rosetta IE32709375, shelfmark 35 V 1770 (catalog NNL_ALEPH990011964030205171).
A Hebrew textbook of astronomy that presents the Ptolemaic model of the heavens for a Hebrew-reading audience, weaving the cutting-edge European science of its day together with the medieval Jewish cosmological tradition — its author having personally visited the Danish astronomer Tycho Brahe.
2
1592 (first composed/printed Prague, שנ”ב; this is a later reprint)
David Gans
Tzemach David
footnotes
National Library of Israel — Rosetta IE90688593 (record labeled “Vol.1-3”).
A Hebrew historical chronicle in two parts by David Gans: the first traces Jewish history from creation to the sixteenth century — biblical figures, sages, and rabbis; the second surveys world and gentile history from Julius Caesar to Emperor Rudolph.
2
1665
Giovanni Battista Riccioli
Astronomia Reformata
footnotes
e-rara ETH-Bibliothek Zürich — title-info 141744
A mature reckoning with the heavens as the telescope was revealing them — a sequel to the vast
Almagestum Novum
(1651), built on further years of observation at Bologna with the collaborator Grimaldi, with fresh measurements and corrected parameters at center stage.
2
c. 1123 (composition; this is a later manuscript copy)
Jacob ben Samson (attrib.)
Perush Sod ha-Ibbur
footnotes
OPenn UPenn-hosted digitization of the British Library manuscript — British Library Add MS 11639, ff. 511r–545v
An early Ashkenazi commentary on the “secret of the calendar” (
sod ha-ibbur
) — the computation of the Hebrew calendar: the molad (lunar conjunction), the tequfot (seasonal points), the nineteen-year intercalation cycle, and the rules governing leap years and festival dates.
2
1629
Joseph Solomon Delmedigo
Sefer Elim
footnotes
Internet Archive — seferelim00delmuoft
A wide-ranging Hebrew scientific compendium, framed as a reply to questions put by the Karaite scholar Zerah ben Nathan.
2
1640
Longomontanus
Astronomia Danica
footnotes
Internet Archive — astronomiadanica00long
A comprehensive textbook of astronomy and the definitive technical account of the Tychonic system — Earth at rest, the Sun circling it, the planets circling the Sun.
2
1654
Pierre Gassendi
Tychonis Brahei Vita
footnotes
Internet Archive — den-kbd-pil-130018157889-001
A life of the Danish astronomer Tycho Brahe (1546–1601): his fabled observatory on the island of Hven, the magnificent instruments he built, the campaigns of observation that remade astronomy, his bold model of the cosmos, and his turbulent final years in Prague.
2
c. 1136
R. Avraham bar Ḥiyya ha-Nasi
Cheshbon Mahalechot ha-Kochavim
footnotes
HebrewBooks.org — ID 22072
A medieval Hebrew treatise on mathematical astronomy and the computation of the Jewish calendar.
2
c. 1122
R. Avraham bar Ḥiyya ha-Nasi
Sefer HaIbbur
footnotes
HebrewBooks.org — ID 21292
The earliest systematic Hebrew treatise on the science of the calendar, written in early-twelfth-century Barcelona.
2
c. 1132
R. Avraham bar Ḥiyya ha-Nasi
Sefer Tsurat ha-Arets
footnotes
NYPL Digital Collections Dorot Jewish Division — item ce668260-c766-0132-045a-58d385a7b928
A foundational work of medieval cosmology that lays out the shape of the cosmos as the Greeks and their Arabic heirs understood it: a spherical earth at the center of nested celestial spheres, the paths of sun and moon, and the zones and geography of the inhabited world.
2
c. 1148
R. Avraham ibn Ezra
Keli ha-Nechoshet
footnotes
HebrewBooks.org — ID 20850
The earliest surviving Hebrew treatise on the astrolabe, composed in the mid-twelfth century.
2
c. 1500
R. Eliyahu Mizrahi
Kitsur ha-Melakhat ha-Mispar
footnotes
NYPL Digital Collections Dorot Jewish Division — item ce668260-c766-0132-045a-58d385a7b928
Kitsur ha-Melakhat ha-Mispar (“Compendium of the Art of Number”) is a Hebrew arithmetic textbook by Rabbi Eliyahu Mizrahi (ca. 1455–1526), the chief rabbi of the Ottoman Empire and one of the foremost Jewish mathematicians of his age.
2
c. 1365
R. Immanuel Bonfils
Shesh Kenafayim
footnotes
University of Pennsylvania — Kislak Center, LJS 204 Digital Scriptorium DS129
One of the most widely copied Hebrew astronomical handbooks of the late Middle Ages, composed around 1365 in Provence.
2
late 14th c. (composition; this is a later manuscript copy)
R. Isaac ibn al-Aḥdab
Keli Ḥemda
footnotes
Gallica / BnF — Hébreu 1031, ff. 208r–215v
Isaac ibn al-Aḥdab’s
Keli Ḥemda
(“The Precious Instrument”) — a description of the construction and use of an equatorium, an instrument for computing planetary positions geometrically.
2
c. 1396 (composed in Syracuse, Sicily; this is a later manuscript copy)
R. Isaac ibn al-Aḥdab
Orah Selulah
footnotes
Gallica / BnF — Hébreu 1086
A set of astronomical tables by Isaac ibn al-Ahdab (Sicily, late 14th c.) for computing the true conjunctions and oppositions of the Sun and Moon — the
Orah Selulah
(“Paved Way”), one of the most widely copied Hebrew astronomical table-works (surviving in ~25 manuscripts).
2
c. 1288 (composition; this is a later manuscript copy)
R. Jacob ben Machir ibn Tibbon
Roba’ Yisrael
footnotes
Gallica / BnF — Hébreu 1031, ff. 131r–147v
Jacob ben Machir ibn Tibbon’s treatise on the
quadrans novus
— the improved astronomical quadrant of his own invention — describing how the instrument is constructed and used for astronomical and time-keeping measurements.
2
c. 1329
R. Levi ben Gershom
Milchamot HaShem
footnotes
Internet Archive — sefermilamothash00leviuoft
The Wars of the Lord is the philosophical and theological masterwork of Levi ben Gershom (Gersonides, 1288–1344), one of the boldest minds of medieval Provence.
2
c. 1328
R. Levi ben Gershom
Sefer HaTechunah
footnotes
Gallica / BnF — MS Hébreu 724, ff. 1r–257v
A complete medieval system of mathematical astronomy, formally Book V, Part 1 of the
Wars of the Lord
.
2
15th c. (composition; this is a later manuscript copy)
R. Mordecai Comtino
Sefer ha-Ḥeshbon ve-ha-Middot
footnotes
Gallica / BnF — Hébreu 1031, ff. 26r–65r
An instructional treatise on arithmetic and practical geometry by Mordecai ben Eliezer Comtino (Constantinople, 15th c.), one of the leading Rabbanite scholars of Byzantine Jewry.
2
1797
R. Pinchas Eliyahu Hurwitz
Sefer HaBrit HaShalem
footnotes
HebrewBooks.org — ID 43670
A sweeping Hebrew encyclopedia of science and mysticism, among the most widely read Hebrew books of its era.
2
c. 1310
R. Yitzchak Yisraeli
Yesod Olam
footnotes
Digital Bodleian — MS. Huntington 299
One of the great medieval Hebrew treatises on astronomy and the science of the Jewish calendar, composed in Toledo in the first half of the fourteenth century.
2
1602
Tycho Brahe
Astronomiae Instauratae Mechanica
footnotes
Internet Archive — gri_tychonisbrah00brah
A sumptuously illustrated catalog of the most accurate astronomical instruments built before the telescope, gathered on the island observatory of Hven.
2
1610
Tycho Brahe
Astronomiae Instauratae Progymnasmata
footnotes
e-rara ETH-Bibliothek Zürich — Rar 4153 DOI 10.3931/e-rara-315, object ID 84169
The fullest statement of the observational program that transformed the science of the heavens.
2
1588
Tycho Brahe
De Mundi Aetherei Recentioribus Phaenomenis
footnotes
Internet Archive — bub_gb_2f-EqKxRN34C
When a brilliant comet blazed across Europe in 1577, the finest instruments of the age were turned upon it, and the measurements shattered the ancient belief in unchanging, perfect heavens: the comet moved freely where solid crystalline spheres were supposed to be.
2
1596
Tycho Brahe
Epistolarum Astronomicarum Libri
footnotes
Internet Archive — tychonisbrahedan00brah
Before scientific journals existed, astronomers argued, boasted, and traded discoveries by letter.
2
c. 150–850 CE
Unknown
Mishnat ha-Middot
footnotes
HebrewBooks.org — ID 39044
The earliest known Hebrew treatise on geometry — a concise practical manual of mensuration covering the areas and perimeters of plane figures, the measurement of circles and segments, and an early value for π.
2
Updates
2026-07-05
Added eight works to the corpus:
Milchamot HaShem
(Gersonides),
Sefer HaBrit HaShalem
(Hurwitz),
Tzemach David
(Gans),
Keli Ḥemda
and
Orah Selulah
(ibn al-Aḥdab),
Roba’ Yisrael
(ibn Tibbon),
Perush Sod ha-Ibbur
(Jacob ben Samson), and
Sefer ha-Ḥeshbon ve-ha-Middot
(Comtino).
Cheshbon Mahalechot ha-Kochavim
(bar Ḥiyya ha-Nasi) was retitled from its earlier heading,
Po’al ha-Shem ve-Cheshbon Mahalechot ha-Kochavim
.
Some works now carry improved source records –
Nechmad ve-Na’im
, for one, now cites the National Library of Israel’s own digitized exemplar.
2026-06-29
All translations are now at
version 2
, regenerated with the corrected pipeline. Version 1 turned out to be an intermediate stage and has been superseded.
Added new works to the corpus – most recently
Sefer Tsurat ha-Arets
,
Kitsur ha-Melakhat ha-Mispar
, and
Sefer Elim
.
Draft editorial footnotes are now available for download from a
footnotes
link beneath each work’s title.
About the translations
Translations are produced with an automated, AI-assisted pipeline that runs each text through a multi-stage workflow before final collation. For technical details, see the translator’s
translation-pipeline
repo.
These translations are prepublication texts – nearly publication-ready, pending the diagrams and illustrations still in progress.
The goal is fluent, readable modern English – a text an educated reader can follow without reaching for the Latin or Hebrew, not one written only for specialists. Rather than reproduce the long periodic sentences and deferred verbs of the originals, the translations carry the author’s meaning, argument, and tone into natural contemporary prose: where Tycho builds a single sentence whose main verb arrives only after four nested clauses, the translation breaks it into the two or three a modern writer would use. Fidelity comes first, though – nothing is dropped, summarized, or invented, and negations, numbers, technical terms, and the author’s own examples and analogies are preserved exactly. Readability never comes at the cost of changing what the source says.
Technical vocabulary stays precise and is anchored to its modern equivalents. A key Latin or Hebrew term of art is glossed on its first occurrence – the original shown alongside the English rendering – and thereafter carried in settled English. Historical names, star names, and specialized vocabulary carry inline identifications: Tycho’s “Lucida Vulturis volantis” is identified as Altair in Aquila; Gersonides’ medieval Hebrew astronomical terminology is mapped to the Ptolemaic system it describes.
Mathematical and astronomical content – sexagesimal values, spherical triangle computations, calendar arithmetic, tabular data – is reproduced with the precision of the originals, cell by cell and degree by degree. Compositor errors in the source are corrected inline with
[recte: …]
notation rather than silently emended. Uncertain readings due to ink damage, worn type, or ambiguous letterforms are marked with
[?]
, preserving the translator’s best reading while flagging it for editorial review.
Illustrations and diagrams
The publicly available PDFs are text-only. Geometric figures, instrument schematics, concentric-sphere charts, and other diagrams from the source works are extracted and replaced with structured descriptions identifying every label, arc, point, and geometric relationship visible in the original woodcut or engraving. Tycho’s
De Mundi Aetherei
, for example, carries 93 such figures, from spherical-astronomy constructions to the two-circle hypothesis of the comet’s eccentric orbit within the solar sphere. For a high-quality illustrated print edition of any of these works, please get in touch using the contact details below.
Support this project
Upright reason dictates that the recipients of the good, of whatever type and level of beneficence it may be, must show gratitude and blessing to the beneficent person in every way possible, commensurate with the value of the beneficence. And one who has benefited all the people of the world – for example, one who invented a new instrument for the good of the world, or a good book – it is fitting for every discerning person, out of the obligation of love of fellow beings, to at least purchase it, so that the man will profit and his heart will be encouraged thereby to invent yet more good instruments in the world. And similarly, all other wise-hearted people will likewise strive and exert themselves to invent good things and instruments needed for the repair of the world and its perfection.
And therefore, whoever says: “What do I need this new instrument for?” – he does not act well towards the world. For if not for the man who invented it, where would you be? And what would your city do? And more than this, if the man did not exert himself, what would the world do?
R. Pinchas Eliyahu Hurwitz,
Sefer HaBrit
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Contact
Email:
[email protected]
X:
@ArsAstronomica
License
The original works are in the public domain and were obtained from a variety of sources, including digitized library collections and other open archives. No claim of ownership is made over the source texts.
All translations in this collection are © Scott Weisman. All rights reserved, except as granted by the license below.
The translations are made available under the
Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
license. You are free to share them for non-commercial purposes with attribution; you may not modify them or use them commercially without prior written permission.
Acknowledgements
Translated with the assistance of Claude. The translator thanks the
Anthropic
team for making this work possible.
