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{{Short description|Astronomical treatise by Claudius Ptolemy}}
{{italic title}}
[[File:Claudius Ptolemaeus, Almagestum, 1515.djvu|page=309|thumb|An edition in Latin of the ''Almagestum'' in 1515]]

The '''''Almagest''''' ({{IPAc-en|ˈ|æ|l|m|ə|dʒ|ɛ|s|t}} {{respell|AL|mə|jest}}) is a 2nd-century [[Greek mathematics|mathematical]] and [[Greek astronomy|astronomical]] treatise on the apparent motions of the [[star]]s and [[planet]]ary paths, written by [[Ptolemy|Claudius Ptolemy]] ({{nowrap|{{circa}} AD 100 –}} {{circa|lk=no|170}}) in [[Koine Greek]].{{sfn|Tomarchio|2022|p=xv}} One of the most influential scientific texts in history, it canonized a [[geocentric model]] of the [[Universe]] that was accepted for more than 1,200 years from its origin in Hellenistic [[Roman-era Alexandria|Alexandria]], in the medieval [[Byzantine]] and [[Islamic Golden Age|Islamic]] worlds, and in Western Europe through the [[Middle Ages]] and early [[Renaissance]] until [[Copernicus]]. It is also a key source of information about ancient [[Greek astronomy]].

Ptolemy set up a public inscription at [[Canopus, Egypt]], in 147 or 148. Norman T. Hamilton found that the version of Ptolemy's models set out in the ''Canopic Inscription'' was earlier than the version in the ''Almagest''. Hence the ''Almagest'' could not have been completed before about 150, a quarter-century after Ptolemy began observing.{{sfn|Hamilton|Swerdlow|1987|p={{Pages needed |date=April 2019}}}}{{sfn|Kunitzsch|2008|pp=140–141}}

{{TOClimit|3}}

== Names ==
The name comes from Arabic {{lang|ar|اَلْمَجِسْطِيّ}} {{transliteration|ar|al-majisṭī}}, with {{lang|ar|اَلـ}} {{transliteration|ar|al-}} meaning '[[definite article|the]]' and {{transliteration|ar|majisṭī}} being a corruption of Greek {{lang|grc|μεγίστη}} {{transliteration|grc|megístē}} 'greatest'. The Arabic name was popularized by a Latin translation known as {{lang|ar|Almagestum}} made in the 12th century from an Arabic translation, which would endure until original Greek copies resurfaced in the 15th century.{{citation needed|date=July 2023}}

The work was originally called {{lang|grc|Μαθηματικὴ Σύνταξις}} ({{Transliteration|grc|Mathēmatikḕ Sýntaxis}}) in [[Koine Greek]], as also in [[Modern Greek]]<ref>{{cite web|title=Κλαύδιος Πτολεμαίος - Μαθηματική Σύνταξις|url=https://www.astrology.gr/astrothesaurus/elliniki-kai-xenoglossi-vivliothiki/story/153209/klaydios-ptolemaios-mathimatiki-syntaxis/amp|access-date=April 3, 2025|language=el|date=October 29, 2021|first=Δέσποινα|last=Γιαννακοπούλου}}</ref><ref>{{cite book|title=ΜΑΘΗΜΑΤΙΚΗ ΣΥΝΤΑΞΙΣ (ΠΡΩΤΟΣ ΤΟΜΟΣ) / ΠΤΟΛΕΜΑΙΟΣ|url=https://www.politeianet.gr/books/9789606716065-ptolemaios-eleutheri-skepsis-mathimatiki-suntaxis-protos-tomos-56272|access-date=April 3, 2025|language=el}}</ref> (primarily),<ref>{{cite web|url=https://schoolpress.sch.gr/testpat1/?p=83|title= Η "Αλμαγέστη"|date=April 14, 2014|access-date=April 3, 2025}}</ref> and was known as {{lang|la|Syntaxis Mathematica}} in [[Latin]]. The treatise was later called {{lang|grc|Ἡ Μεγάλη Σύνταξις}} ({{Transliteration|grc|Hē Megálē Sýntaxis}}), "The Great Treatise" ({{langx|la|Magna Syntaxis|links=no}}), and the superlative form of this ({{langx|grc|μεγίστη|label=Greek}} {{Transliteration|grc|megístē}}, 'greatest') lies behind the Arabic name from which the English name ''Almagest'' derives.

In the study of medieval Hebrew texts, the ''Almagest'' is sometimes referred to as "Ptolemy's ''Book of [[Electional astrology|Elections]]''",<ref>{{cite web|url=https://braginskycollection.com/portfolio/astronomical-and-astrological-miscellany/|website=Braginsky Collection|title=Astronomical and astrological miscellany|year=2016|first=Ardon|last=Bar-Hama}}</ref> to emphasize parallelism with [[Abraham ibn Ezra]]'s manuscript of the same name.<ref>{{cite book|title=Abraham Ibn Ezra on Elections, Interrogations, and Medical Astrology|series=Études sur le judaïsme médiéval|volume=50|first=Shlomo|last=Sela|date=9 Sep 2011|isbn=978-90-04-21445-3}}</ref>

==History==
Written possibly around 150 CE, the text survives as copies, the oldest being from the 9th century<ref name="o547">{{cite web | title=Grec 2389 | website=Gallica | url=https://gallica.bnf.fr/ark:/12148/btv1b8470171d | language=fr | access-date=2024-11-23}}</ref> when Arabic scholars started to translate the text, which in turn have survived in copies from the 11th<ref name="p866">{{cite web | title=PAL: Tunis, Dār al-kutub al-waṭaniyya, 7116 | website=Ptolemaeus Arabus et Latinus | date=2024-10-23 | url=https://ptolemaeus.badw.de/ms/669 | access-date=2024-11-23}}</ref> and 13th<ref name="h341">{{cite web | title=al- Miǵisṭī (translation of Ptolemy) Or. 680 | website=Digital Collections | url=https://digitalcollections.universiteitleiden.nl/view/item/1871093#page/1/mode/1up | language=af | access-date=2024-11-23}}</ref><ref name="i465">{{cite web | title=PAL: Ptolemy, al-Majisṭī (tr.al-Ḥajjāj) | website=Ptolemaeus Arabus et Latinus | date=2024-11-14 | url=https://ptolemaeus.badw.de/work/200 | access-date=2024-11-23}}</ref> centuries.<ref name="k352">{{cite journal | last=Zieme | first=Stefan | title=Gerard of Cremona's Latin translation of the Almagest and the revision of tables | journal=Journal for the History of Astronomy | volume=54 | issue=1 | date=2023 | issn=0021-8286 | doi=10.1177/00218286221140848 | doi-access=free | pages=3–33| bibcode=2023JHA....54....3Z }}</ref>

== Contents ==
=== The ''Syntaxis Mathematica'' books ===
[[File:Ptolemy-4.jpg|alt=Table of contents to a 1528 copy of Almagest, translated to Latin from Greek by George of Trebizond|thumb|Table of contents to a 1528 copy of ''Almagest'', translated to Latin from Greek by [[George of Trebizond]]]]

The ''Syntaxis Mathematica'' consists of thirteen sections, called books. As with many medieval manuscripts that were handcopied or, particularly, printed in the early years of printing, there were considerable differences between various editions of the same text, as the process of transcription was highly personal. An example illustrating how the ''Syntaxis'' was organized is given below; it is a Latin edition printed in 1515 at Venice by Petrus Lichtenstein.{{sfn|Lichtenstein|1515|p={{Pages needed|date=April 2023}}}}

* '''Book I''' contains an outline of [[Aristotle]]'s cosmology: on the spherical form of the heavens, with the spherical Earth lying motionless as the center, with the [[fixed stars]] and the various [[planets]] revolving around the Earth. Then follows an explanation of [[chord (geometry)|chords]] with [[Ptolemy's table of chords|table of chords]]; observations of the obliquity of the [[ecliptic]] (the apparent path of the Sun through the stars); and an introduction to [[spherical trigonometry]].
* '''Book II''' covers problems associated with the daily motion attributed to the heavens, namely risings and settings of celestial objects, the length of daylight, the determination of [[latitude]], the points at which the [[Sun]] is vertical, the shadows of the [[gnomon]] at the [[equinox]]es and [[solstice]]s, and other observations that change with the observer's position. There is also a study of the angles made by the ecliptic with the vertical, with tables.
* '''Book III''' covers the length of the year, and the motion of the [[Sun]]. Ptolemy explains [[Hipparchus]]' discovery of the [[Precession (astronomy)|precession]] of the equinoxes and begins explaining the theory of [[epicycles]].
* '''Books IV''' and '''V''' cover the motion of the [[Moon]], lunar [[parallax]], the motion of the lunar [[apogee]], and the sizes and distances of the Sun and Moon relative to the Earth.
* '''Book VI''' covers solar and lunar [[eclipse]]s.
* '''Books VII''' and '''VIII''' cover the motions of the fixed stars, including precession of the equinoxes. They also contain a [[star catalogue]] of 1022 stars, described by their positions in the [[constellation]]s, together with [[ecliptic coordinates|ecliptic longitude and latitude]].{{refn|1= The catalogue actually contained 1,028 entries, but three of these were deliberate duplicates, because Ptolemy regarded certain stars as being shared between adjacent constellations. Three other entries were non-stellar, i.e. the Double Cluster in Perseus, M44 (Praesepe) in Cancer, and the globular cluster Omega Centauri.{{sfn|Ridpath|2023|loc=[http://www.ianridpath.com/startales/almagest.html "Ptolemy’s Almagest"]}} Ptolemy states that the longitudes (which increase due to [[precession]]) are for the beginning of the reign of [[Antoninus Pius]] (138 AD), whereas the latitudes do not change with time (but see [[#The star catalogue|the star catalog]]). The constellations north of the [[zodiac]] and the northern zodiac constellations (Aries through Virgo) are in the table at the end of Book VII, while the rest are in the table at the beginning of Book VIII. The brightest stars were marked first [[apparent magnitude|magnitude]] ({{mvar|m}}&nbsp;=&nbsp;1), while the faintest visible to the naked eye were sixth magnitude ({{mvar|m}}&nbsp;=&nbsp;6). Each numerical magnitude was considered twice the brightness of the following one, which is a [[logarithmic scale]]. (The ratio was subjective as no [[photodetector]]s existed.) This system is believed to have originated with Hipparchus. The stellar positions too are of Hipparchan origin, despite Ptolemy's claim to the contrary. Ptolemy identified 48 constellations: The 12 of the [[zodiac]], 21 to the north of the zodiac, and 15 to the south.{{sfn|Ridpath|2023|loc=[http://www.ianridpath.com/startales/almagest.html#48 Ptolemy’s 48 constellations]}}|group=note}}
* '''Book IX''' addresses general issues associated with creating models for the five [[naked eye planet]]s, and the motion of [[Mercury (planet)|Mercury]].
* '''Book X''' covers the motions of [[Venus]] and [[Mars]].
* '''Book XI''' covers the motions of [[Jupiter]] and [[Saturn]].
* '''Book XII''' covers stations and [[apparent retrograde motion|retrograde motion]], which occurs when planets appear to pause, then briefly reverse their motion against the background of the zodiac. Ptolemy understood these terms to apply to Mercury and Venus as well as the outer planets.
* '''Book XIII''' covers motion in latitude, that is, the deviation of planets from the ecliptic. The final topic of this chapter also covers how to determine when a planet first becomes visible after being hidden by the glare of the sun, as well as the last time it is seen before being hidden by the sun's glare.

=== Ptolemy's cosmos ===
The cosmology of the ''Syntaxis'' includes five main points, each of which is the subject of a chapter in Book I. What follows is a close paraphrase of Ptolemy's own words from Toomer's translation.{{sfn|Toomer|1984|p={{Pages needed|date=April 2023}}}}

* The celestial realm is spherical, and moves as a sphere.
* The Earth is a sphere.
* The Earth is at the center of the cosmos.
* The Earth, in relation to the distance of the fixed stars, has no appreciable size and must be treated as a mathematical point.{{sfn|Ptolemy|1952|loc= Book I, Chapter 5, p.9}}
* The Earth does not move.

=== The star catalogue ===
[[File:Manuskript Ptolemy Labelled.png|thumb|Example of a Greek manuscript of the Almagest, showing a table layout for the stars of Ursa Minor. The functions of the columns, colours and rows are labelled in this depiction.]]

The layout of the catalogue has always been tabular.{{sfn|Lichtenstein|1515|p=[https://daten.digitale-sammlungen.de/bsb00001192/images/index.html?id=00001192&groesser=&fip=xsxseayayztseayaeayafsdrxdsydeayaqrsfsdr&no=3&seite=161 79]}} Ptolemy writes explicitly that the coordinates are given as (ecliptical) "longitudes" and "latitudes", which are given in columns, so this has probably always been the case. It is significant that Ptolemy chooses the ecliptical coordinate system because of his knowledge of precession, which distinguishes him from all his predecessors. Hipparchus' celestial globe had an ecliptic drawn in, but the coordinates were equatorial.{{sfn|Hoffmann|2017|p={{Pages needed|date=April 2023}}}} Since Hipparchus' star catalogue has not survived in its original form, but was absorbed into the Almagest star catalogue (and heavily revised in the 265 years in between),{{sfn|Hoffmann|2018|p={{Pages needed|date=April 2023}}}}{{sfn|Hoffmann|2017|p={{Pages needed|date=April 2023}}}} the Almagest star catalogue is the oldest one in which complete tables of coordinates and magnitudes have come down to us.

As mentioned, Ptolemy includes a star catalog containing 1022 stars. He says that he "observed as many stars as it was possible to perceive, even to the sixth magnitude". The [[ecliptic longitude]]s are given in terms of a zodiac sign and a number of degrees and fractions of a degree. The zodiac signs each represent exactly 30°, starting with [[Aries (constellation)|Aries]] representing longitude 0° to 30°. The degrees are added to the lower limit of the 30-degree range to obtain the longitude. Unlike the situation with the [[zodiac]] of modern-day [[astrology]], most of the stars of a given zodiac constellation in the catalog fall in the 30-degree range designated by the same name (the so-called 'zodiac sign'). The ecliptic longitudes are about 26° lower than those of AD&nbsp;2000 (the [[J2000]] epoch).{{refn|1= For instance, the stars [[nu Orionis]] and [[62 Orionis]] which are now around ecliptic longitude 91° are attributed longitudes in the Almagest of 66° and 64°20' respectively.|group=note}} Ptolemy says that the ecliptic longitudes are for the beginning of the reign of [[Antoninus Pius]] (138 AD) and that he found that the longitudes had increased by 2° 40′ since the time of [[Hipparchus]] which was 265 years earlier (Alm. VII, 2). But calculations show that his ecliptic longitudes correspond more closely to around the middle of the first century CE (+48 to +58).{{sfn|Toomer|1984|p={{Pages needed|date=April 2023}}}}{{sfn|Graßhoff|1990|p={{Pages needed|date=April 2023}}}}{{sfn|Hoffmann|2017|p={{Pages needed|date=April 2023}}}}

Since Tycho Brahe found this offset, astronomers and historians investigated this problem and suggested several causes:

* that all coordinates were calculated from Hipparchus' observations, whereby the precession constant, which was known too inaccurately at the time, led to a summation error (Delambre 1817);{{sfn|Graßhoff|1990|p={{Pages needed|date=April 2023}}}}{{sfn|Peters|Knobel|1915|p=[https://archive.org/details/cu31924012300491/page/n30/mode/1up 15]}}
* that the data had in fact been observed a century earlier by Menelaus of Alexandria (Björnbo 1901);{{sfn|Graßhoff|1990|p={{Pages needed|date=April 2023}}}}
* that the difference is a sum of individual errors of various kinds, including calibration with outdated solar data;{{sfn|Dreyer|1917|p=528}}{{sfn|Graßhoff|1990|p={{Pages needed|date=April 2023}}}}
* that Ptolemy's instrument was wrongly calibrated and had a systematic offset.{{sfn|Vogt|1925|pp=17–54}}

[[File:Errors in Ptolemy’s star catalogue.svg|thumb|upright=1.35|Errors in Ptolemy’s star catalogue: In blue are the stars in the Almagest’s list; in orange, the points of modern measurements transformed to the second century, taking proper motion into account; the orange and blue band is the ecliptic; and the blue curve is the equator. Figure inspired by Hoffmann 2017.{{sfn|Hoffmann|2017|p={{Pages needed|date=April 2023}}}}]]

Subtracting the systematic error leaves other errors that cannot be explained by precession. Of these errors, about 18 to 20 are also found in Hipparchus' star catalogue (which can only be reconstructed incompletely).{{sfn|Vogt|1925|pp=17–54}}{{sfn|Hoffmann|2017|p={{Pages needed|date=April 2023}}}} From this it can be concluded that a subset of star coordinates in the Almagest can indeed be traced back to Hipparchus,{{sfn|Graßhoff|1990|p={{Pages needed|date=April 2023}}}} but not that the complete star catalogue was simply "copied". Rather, Hipparchus' major errors are no longer present in the Almagest{{sfn|Hoffmann|2017|p={{Pages needed|date=April 2023}}}} and, on the other hand, Hipparchus' star catalogue had some stars that are entirely absent from the Almagest.{{sfn|Hoffmann|2017|p={{Pages needed|date=April 2023}}}} It can be concluded that Hipparchus' star catalogue, while forming the basis, has been reobserved and revised.{{sfn|Hoffmann|2017|p={{Pages needed|date=April 2023}}}}{{sfn|Hoffmann|2018|p={{Pages needed|date=April 2023}}}}

==== Errors in the coordinates ====
The figure he used is based on Hipparchus' own estimate for precession, which was 1° in 100 years, instead of the correct 1° in 72 years. Dating attempts through [[proper motion]] of the stars also appear to date the actual observation to Hipparchus' time instead of Ptolemy.{{sfn|Dambis|Efremov|2000|pp=115–134}}

Many of the longitudes and latitudes have been corrupted in the various manuscripts. Most of these errors can be explained by similarities in the symbols used for different numbers. For example, the Greek letters Α and Δ were used to mean 1 and 4 respectively, but because these look similar copyists sometimes wrote the wrong one. In Arabic manuscripts, there was confusion between for example 3 and 8 (ج and ح). (At least one translator also introduced errors. [[Gerard of Cremona]], who translated an Arabic manuscript into Latin around 1175, put 300° for the latitude of several stars. He had apparently learned from [[Moors]], who [[Abjad numerals|used the letter س (sin) for 300]] (like the Hebrew [[Shin (letter)#Hebrew shin/sin|ש (shin)]]), but the manuscript he was translating came from the East, where س was used for 60, [[Hebrew numerals|like the Hebrew ס (samekh)]].){{sfn|Peters|Knobel|1915|pp=[https://archive.org/details/cu31924012300491/page/n24/mode/1up 9–14]}}

Even without the errors introduced by copyists, and even accounting for the fact that the longitudes are more appropriate for 58 AD than for 137 AD, the latitudes and longitudes are not fully accurate, with errors as great as large fractions of a degree. Some errors may be due to [[atmospheric refraction]] causing stars that are low in the sky to appear higher than where they really are.{{sfn|Peters|Knobel|1915|p=[https://archive.org/details/cu31924012300491/page/n29/mode/1up 14]}} A series of stars in [[Centaurus]] are off by a couple of degrees, including the star we call [[Alpha Centauri]]. These were probably measured by a different person or persons from the others, and in an inaccurate way.{{sfn|Peters|Knobel|1915|p=[https://archive.org/details/cu31924012300491/page/n133/mode/1up 112]}}

==== Constellations in the star catalogue ====
The star catalogue contains 48 constellations, which have different surface areas and numbers of stars. In Book VIII, Chapter 3, Ptolemy writes that the constellations should be outlined on a globe, but it is unclear exactly how he means this: should surrounding polygons be drawn or should the figures be sketched or even line figures be drawn? This is not stated.

Although no line figures have survived from antiquity, the figures can be reconstructed on the basis of the descriptions in the star catalogue: The exact celestial coordinates of the figures' heads, feet, arms, wings and other body parts are recorded.{{sfn|Hoffmann|2017|p={{Pages needed|date=April 2023}}}} It is therefore possible to draw the stick figures in the modern sense so that they fit the description in the Almagest.{{refn|1= These modern stick figures as a reconstruction of the historical constellations of the Almagest are available in the free planetarium software [[Stellarium (software)|Stellarium]] since 2019.{{citation needed|date=April 2023}}|group=note}}

These constellations form the basis for the modern [[constellation]]s that were formally adopted by the International Astronomical Union in 1922, with official boundaries that were agreed in 1928.

Of the stars in the catalogue, 108 (just over 10%) were classified by Ptolemy as 'unformed', by which he meant lying outside the recognized constellation figures. These were later absorbed into their surrounding constellations or in some cases used to form new constellations.{{sfn|Ridpath|2023|loc=[http://www.ianridpath.com/startales/ptolemy-spare.html "How Ptolemy’s spare stars became new constellations"]}}

=== Ptolemy's planetary model ===
[[File:Ptolemaicsystem-small.png|thumb|16th-century representation of Ptolemy's [[geocentric model]] in [[Peter Apian]]'s ''Cosmographia'', 1524]]

In Almagest, Ptolemy assigned the following order to the [[planetary spheres]], beginning with the innermost:<ref>See Book IX, Chapter I, "On the order o f the spheres o f sun, moon and the 5 planets" in the Toomer's translation.</ref>
{{Colbegin|colwidth=30em}}
# Moon
# Mercury or Venus (undecided)<ref>For example, in Albert Van Helden , Measuring the Universe Cosmic Dimensions from Aristarchus to Halley, Chicago University Press, 1985, page 20, it is stated that "He left the order of Venus and Mercury with respect to each other undecided in the Almagest."</ref>
# Mercury or Venus (undecided)
# Sun
# Mars
# Jupiter
# Saturn
# Sphere of fixed stars
{{colend}}

Later, in his "Planetary Hypothesis", he concludes that Mercury is the second closest planet. Other classical writers suggested different sequences. [[Plato]] ({{Circa|427|347 BC}}) placed the Sun second in order after the Moon. [[Martianus Capella]] (5th century AD) put Mercury and Venus in motion around the Sun. Ptolemy's authority was preferred by most [[Astronomy in medieval Islam|medieval Islamic]] and late medieval European astronomers. <!-- Comparison with Aristotle's model should be added -->

Ptolemy inherited from his Greek predecessors a geometrical toolbox and a partial set of models for predicting where the planets would appear in the sky. [[Apollonius of Perga]] ({{Circa|262|190 BC}}) had introduced the [[deferent and epicycle]] and the eccentric deferent to astronomy. Hipparchus (2nd century BC) had crafted mathematical models of the motion of the Sun and Moon. Hipparchus had some knowledge of [[History of Astronomy#Mesopotamia|Mesopotamian astronomy]], and he felt that Greek models should match those of the Babylonians in accuracy. He was unable to create accurate models for the remaining five planets.

[[File:HipparchusConstruction.svg|thumb|upright=1.35 |Geometric construction used by Hipparchus in his determination of the distances to the Sun and Moon, which was later incorporated into Ptolemy's work]]

The ''Syntaxis'' adopted Hipparchus' solar model, which consisted of a simple eccentric deferent. For the Moon, Ptolemy began with Hipparchus' epicycle-on-deferent, then added a device that historians of astronomy refer to as a "crank mechanism":{{sfn|Hoskin|1999|p=44}} he succeeded in creating models for the other planets, where Hipparchus had failed, by introducing a third device called the [[equant]].

Ptolemy wrote the ''Syntaxis'' as a textbook of mathematical astronomy. It explained geometrical models of the planets based on combinations of circles, which could be used to predict the motions of celestial objects. In a later book, the ''Planetary Hypotheses'', Ptolemy explained how to transform his geometrical models into [[three-dimensional space|three-dimensional spheres]] or partial spheres. In contrast to the mathematical ''Syntaxis'', the ''Planetary Hypotheses'' is sometimes described as a book of [[cosmology]].

== Influence ==
[[File:Ptolemy 16century.jpg|thumb|Ptolemy's ''Almagest'' became an authoritative work for many centuries.]]
[[File:Almagest 1.jpeg|thumb|Picture of [[George of Trebizond]]'s Latin translation of the ''Syntaxis Mathematica'' or ''Almagest'']]

Ptolemy's comprehensive treatise of mathematical astronomy superseded most older texts of Greek astronomy. Much of what we know about the work of astronomers like Hipparchus comes from references in the ''Syntaxis''.

The book was circulated among astronomers,  and also among philosophers who are interested in astronomy. The Almagest, however, was not translated into Latin in ancient times and had little influence on popular literature.

The first translations into Arabic were made in the 9th century, with two separate efforts, one sponsored by the [[caliph]] [[Al-Ma'mun]], who received a copy as a condition of peace with the Byzantine emperor.{{sfn|Angelo|2006|p=78}} [[Sahl ibn Bishr]] is thought to be the first Arabic translator.

No Latin translation was made before the 12th century. [[Henry Aristippus]] made the first Latin translation directly from a Greek copy, but it was not as influential as a later translation into Latin made in [[Spain]] by the Italian scholar [[Gerard of Cremona]] from the Arabic (finished in 1175).{{sfn|Toomer|1984|p=[https://books.google.com/books?id=6tNFAQAAIAAJ&q=Gerard+of+Cremona 3]}}{{sfn|Kunitzsch|1986|p=89}} Gerard translated the Arabic text while working at the [[Toledo School of Translators]], although he was unable to translate many technical terms such as the Arabic ''Abrachir'' for Hipparchus. In the 13th century a Spanish version was produced, which was later translated under the patronage of [[Alfonso X]].

In the 15th century, a Greek version appeared in Western Europe. The German astronomer Johannes Müller (known as [[Regiomontanus]], after his birthplace of [[Königsberg, Bavaria|Königsberg]] in Lower Frankonia)  made an abridged Latin version at the instigation of the Greek churchman [[Bessarion|Cardinal Bessarion]]. Around the same time, [[George of Trebizond]] made a full translation accompanied by a commentary that was as long as the original text. George's translation, done under the patronage of [[Pope Nicholas V]], was intended to supplant the old translation. The new translation was a great improvement; the new commentary was not, and aroused criticism.{{sfn|Shank|2020|pp=305–307}} The Pope declined the dedication of George's work,{{sfn|Shank|2020|pp=305–307}} and Regiomontanus's translation had the upper hand for over 100 years.{{citation needed|date=April 2023}}

During the 16th century, [[Guillaume Postel]], who had been on an embassy to the [[Ottoman Empire]], brought back Arabic disputations of the ''Almagest'', such as the works of [[al-Kharaqī]], {{lang|ar-Latn|Muntahā al-idrāk fī taqāsīm al-aflāk}} ("The Ultimate Grasp of the Divisions of Spheres", 1138–39).{{sfn|Saliba|2011|pp=217–221}}

Commentaries on the ''Syntaxis'' were written by [[Theon of Alexandria]] (extant), [[Pappus of Alexandria]] (only fragments survive), and [[Ammonius Hermiae]] (lost).

== Modern assessment ==
Under the scrutiny of modern scholarship, and the cross-checking of observations contained in the Almagest against figures produced through backwards extrapolation, various patterns of errors have emerged within the work.{{sfn|Wade|1977}}{{sfn|Lewis|1979}} A prominent example is Ptolemy's use of measurements said to have been taken at noon, but which systematically produce readings that are off by half an hour, as if the observations were taken at 12:30pm.{{sfn|Wade|1977}} However, an explanation for this error was found in 1969.{{sfn|Goldstein|1978}}{{sfn|Britton|1969}}{{sfn|Britton|1992}}

The overall quality of Claudius Ptolemy's scholarship and place as "one of the most outstanding scientists of antiquity" has been challenged by several modern writers, most prominently by [[Robert R. Newton]] in the 1977 book ''The Crime of Claudius Ptolemy'', which asserted that the scholar fabricated his observations to fit his theories. Newton accused Ptolemy of systematically inventing data or doctoring the data of earlier astronomers, and labelled him "the most successful fraud in the history of science".{{sfn|Wade|1977}} One striking error noted by Newton was an autumn equinox said to have been observed by Ptolemy and "measured with the greatest care" at 2pm on 25 September 132, when the equinox should have been observed at 9:54am the day prior.{{sfn|Wade|1977}}
Herbert Lewis, who had reworked some of Ptolemy's calculations, agreed with Newton that "Ptolemy was an outrageous fraud", and that "all those results capable of statistical analysis point beyond question towards fraud and against accidental error".{{sfn|Lewis|1979}}

Although some have described the charges laid by Newton as "erudite and imposing", others have disagreed with the findings.{{sfn|Wade|1977}} [[Bernard R. Goldstein]] wrote, "Unfortunately, Newton’s arguments in support of these charges are marred by all manner of distortions, misunderstandings, and excesses of rhetoric due to an intensely polemical style."{{sfn|Goldstein|1978}} [[Owen Gingerich]], while agreeing that the Almagest contains "some remarkably fishy numbers",{{sfn|Wade|1977}} including in the matter of the 30-hour displaced equinox, which he noted aligned perfectly with predictions made by [[Hipparchus]] 278 years earlier,{{sfn|Gingerich|1980}} rejected the qualification of fraud.{{sfn|Wade|1977}}{{sfn|Gingerich|1981}}
John Phillips Britton, Visiting Fellow at Yale University, wrote of R.R. Newton, "I think that his main conclusion with respect to Ptolemy’s stature and achievements as an astronomer is simply wrong, and that the Almagest should be seen as a great, if not indeed the first, scientific treatise." He continued, "Newton’s work does focus critical attention on the many difficulties and inconsistencies apparent in the fine structure of the Almagest. In particular, his conclusion that the Almagest is not a historical account of how Ptolemy actually derived his models and parameters is essentially the same as mine, although our reasons for this conclusion and our inferences from it differ radically."{{sfn|Britton|1992}}

== Modern editions ==
The ''Almagest'' under the Latin title ''Syntaxis mathematica'', was edited by [[Johan Ludvig Heiberg (historian)|J. L. Heiberg]] in ''Claudii Ptolemaei opera quae exstant omnia'', vols. 1.1 and 1.2 (1898, 1903).

[[File:Ptolemy-2.jpg|alt=1528 copy of a Latin translation of "Almagestum", translated from Greek by George of Trebizond|thumb|247x247px|1528 copy of a Latin translation of "Almagestum", translated from Greek by [[George of Trebizond]]]]

Three translations of the ''Almagest'' into English have been published. The first, by [[R. Catesby Taliaferro]] of [[St. John's College (Annapolis/Santa Fe)|St. John's College]] in [[Annapolis, Maryland]], was included in volume 16 of the ''[[Great Books of the Western World]]'' in 1952. The second, by [[G. J. Toomer]], ''Ptolemy's Almagest'' in 1984, with a second edition in 1998.{{sfn|Toomer|1984}} The third was a partial translation by Bruce M. Perry in ''The Almagest: Introduction to the Mathematics of the Heavens'' in 2014.{{sfn|Ptolemy|2014}}

A direct French translation from the Greek text was published in two volumes in 1813 and 1816 by [[Nicholas Halma]], including detailed historical comments in a 69-page preface. It has been described as "suffer[ing] from excessive literalness, particularly where the text is difficult" by Toomer, and as "very faulty" by Serge Jodra.{{sfn|Jodra|2013}} The scanned books are available in full at the ''[[Gallica]]'' French National library.{{sfn|Halma|1813}}{{sfn|Halma|1816}}

A new French translation, with some interactive diagrams, was prepared in 2022 and is freely available on the web.<ref>{{cite web |last=Paquette |first=Pierre |date=2022 |title=L’Almageste de Ptolémée |url=http://ecliptiqc.ca/Almageste.php |website=EcliptiQc |location=Canada |publisher=Pierre Paquette |access-date=2025-09-08 }}</ref>

== Gallery ==
<gallery>
Ptolemy's cataloque of stars.djvu|page=9|Ptolemy's catalogue of stars; a revision of the ''Almagest'' by Christian Heinrich Friedrich Peters and Edward Ball Knobel, 1915
File:Epytoma Ioannis de Monte Regio in Almagestum Ptolomei.djvu|page=9|Epytoma Ioannis de Monte Regio in ''Almagestum'' Ptolomei, Latin, 1496
File:Claudius Ptolemaeus, Almagestum, 1515.djvu|page=2|''Almagestum'', Latin, 1515
</gallery>

== See also ==
* [[Abū al-Wafā' Būzjānī]] (who also wrote an ''Almagest'')
* ''[[Book of Fixed Stars]]''
* [[Star cartography]]
* [[Euclid's Elements|Euclid's ''Elements'']]

== References ==
=== Notes ===
{{reflist|group=note}}

=== Citations ===
{{reflist|20em}}

=== Sources ===
==== Books ====
{{refbegin}} 
* {{cite book
 |last= Angelo
 |first= Joseph A. Jr.
 |title= Encyclopedia of Space and Astronomy
 |date= 2006
 |edition= 1st
 |location= New York
 |publisher= Facts on File
 |isbn= 978-0-8160-5330-8
 |url= https://books.google.com/books?id=VUWno1sOwnUC&q=Al+Ma'mun+Almagest+peace+treaty&pg=PA78
 |via= books.google.com
}}
* {{cite book
 |last= Britton
 |first= John Phillips
 |title= Models and Precision: The Quality of Ptolemy's Observations and Parameters
 |date= 1992
 |place= New York
 |publisher= Garland
 |isbn= 0-8153-0215-0
 |url= https://archive.org/details/modelsprecisionq00brit/
}}
* {{cite book
 |last= Graßhoff
 |first= Gerd
 |title= The History of Ptolemy's Star Catalogue 
 |date= 1990
 |series= Studies in the History of Mathematics and Physical Sciences
 |volume= 14
 |location= Berlin
 |publisher= Springer
 |isbn= 3-540-97181-5
 |doi= 10.1007/978-1-4612-4468-4
 |url= https://archive.org/details/historyofptolemy0000gras/
 |url-access= limited
}}{{Pages needed|date=April 2023}}
* {{cite book
 |last= Halma
 |first= Nicolas
 |author-link= Nicholas Halma
 |date= 1813
 |title= Composition mathématique de Claude Ptolémée
 |volume= 1
 |language= fr
 |location= Paris
 |publisher= J. Hermann
 |url= https://gallica.bnf.fr/ark:/12148/bpt6k64767c.pdf
 |via = [[Bibliothèque nationale de France]]
}}
* {{cite book
 |last= Halma
 |first= Nicolas
 |author-mask=1
 |date= 1816
 |title= Composition mathématique de Claude Ptolémée
 |volume= 2
 |language= fr
 |location= Paris
 |publisher= H. Grand
 |url= https://gallica.bnf.fr/ark:/12148/bpt6k61815p.pdf
 |via = [[Bibliothèque nationale de France]]
}}
* {{cite book
 |last1= Hamilton
 |first1= N. T.
 |last2= Swerdlow
 |first2= N. M.
 |editor-last1= Berggren
 |editor-first1= J. L.
 |editor-last2= Goldstein
 |editor-first2= B. R.
 |title= From Ancient Omens to Statistical Mechanics
 |chapter= The Canobic Inscription: Ptolemy's Earliest Work
 |date= 1987
 |publisher= [[Copenhagen University Library]]
 |isbn= 978-8-7770-9002-8
}}{{Pages needed |date=April 2019}}
* {{cite book
 |last= Hoffmann
 |first= Susanne M.
 |title= Hipparchs Himmelsglobus 
 |language= de
 |date= 2017
 |location= Berlin
 |publisher= Springer
 |isbn= 978-3-658-18682-1
 |doi= 10.1007/978-3-658-18683-8
 |bibcode= 2017hihi.book.....H
}}{{Pages needed|date=April 2023}}
* {{cite book
 |last= Hoskin
 |first= Michael 
 |editor-last= Hoskin
 |editor-first= Michael 
 |title= The Cambridge Concise History of Astronomy
 |chapter= 2. Astronomy in Antiquity
 |date= 1999
 |edition= 1st
 |location= [[Cambridge]], England
 |publisher= [[Cambridge University Press]]
 |isbn= 978-0-521-57291-0
}}
* {{cite encyclopedia
 |last= Kunitzsch
 |first= Paul
 |editor-last= Selin
 |editor-first= Helaine
 |encyclopedia= Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures
 |title= Almagest: Its Reception and Transmission in the Islamic World 
 |language= English
 |date= 2008
 |pages= 140–141
 |edition= 2nd
 |orig-date= 1997
 |location= Berlin
 |publisher= Springer
 |isbn= 978-1-4020-4559-2
 |doi= 10.1007/978-1-4020-4425-0_8988
 |quote= Around AD 150, Ptolemy wrote his great handbook of astronomy called ''Mathematike Syntaxis''...
}}
* {{cite book
 |last= Lichtenstein
 |first= Petrus
 |title= Claudius Ptolemaeus Almagestum
 |date= 1515
 |language= La
 |location= Venice 
 |url= https://dokumen.tips/documents/claudius-ptolemaeus-almagestum-1515.html
 |oclc= 644484399
 |access-date= 31 May 2014
 |via= Astronomy Library of the Vienna University
}}
* {{cite book
 |last1= Peters
 |first1= Christian Heinrich Friedrich
 |author-link1= Christian Heinrich Friedrich Peters
 |last2= Knobel
 |first2= Edward Ball
 |author-link2= Edward Knobel
 |title= Ptolemy's Catalogue of the Stars – A Revision of the Almagest
 |date= 1915
 |publisher= [[Carnegie Institution of Washington]]
 |volume= 86 
 |url= https://archive.org/details/cu31924012300491/page/n11/mode/2up
}}
* {{cite book
 |last= Ptolemy
 |first= Claudius
 |author-link= Ptolemy
 |date= 1952
 |editor1-last= Hutchins |editor1-first= Robert Maynard |editor1-link= Robert Maynard Hutchins 
 |editor2-last= Adler |editor2-first= Mortimer J. |editor2-link= Mortimer J. Adler 
 |contribution= The Almagest <!-- |at= Book I, Chapter 5, p.9 -->
 |title=Ptolemy, Copernicus, Kepler
 |place=Chicago
 |publisher= Encyclopaedia Brittanica, Inc
 |url= https://archive.org/details/in.ernet.dli.2015.547436/page/n23
}}
* {{cite book
 |last= Ptolemy
 |first= Claudius
 |author-mask=1
 |translator-last= Perry
 |translator-first= Bruce M.  
 |editor-last= Donahue
 |editor-first= William H. 
 |title= The Almagest: Introduction to the Mathematics of the Heavens
 |language= English
 |date= 2014
 |location= [[Santa Fe, New Mexico|Santa Fe]], NM
 |publisher= Green Lion Press
 |isbn= 978-1-88800-943-9
}}
* {{Cite book
 |last= Saliba
 |first= George
 |author-link= George Saliba
 |editor-last= Buchwald |editor-first= Jed Z.
 |date= 2011 |orig-date= 2007
 |title= Islamic Science and the Making of European Renaissance
 |edition= 2nd
 |location= Cambridge, Mass. |publisher= [[MIT Press]]
 |isbn= 978-0-262-51615-0
}}
* {{cite book
 |last= Shank
 |first= Michael H.
 |date= 2020
 |chapter= Regiomontanus ''versus'' George of Trebizond on Planetary Order, Distances, and Orbs (''Almagest'' 9.1)
 |editor-last1= Juste
 |editor-first1= David
 |editor-last2= van Dalen
 |editor-first2= Benno
 |editor-last3= Hasse
 |editor-first3= Dag Nikolaus
 |editor-last4= Burnett
 |editor-first4= Charles
 |title= Ptolemy's Science of the Stars in the Middle Ages
 |series= Ptolemaeus Arabus et Latinus
 |pages= 305–307
 |location= Turnhout
 |publisher= Brepols
 |chapter-url= https://www.brepolsonline.net/doi/pdf/10.1484/M.PALS-EB.5.120184
 |isbn= 978-2-503-58639-7
 |doi= 10.1484/M.PALS-EB.5.120189
 |doi-access=free
}}
* {{cite book
 |last= Tomarchio
 |first= John
 |date= 2022
 |title= A Sourcebook for Ancient Greek: Grammar, Poetry, and Prose
 |location= Washington, D.C.
 |publisher= [[CUA Press]]
 |isbn= 978-1-949822-20-5
 |url= https://books.google.com/books?id=_dOUEAAAQBAJ
}}
* {{cite book
 |last= Toomer
 |first= G. J.
 |author-link= G. J. Toomer
 |date= 1984
 |title= Ptolemy's Almagest
 |location= London
 |publisher= [[Duckworth Books]]
 |isbn= 978-0-387-91220-2
}}
{{refend}}

====Journals and magazines====
{{refbegin}}
* {{cite journal
 |last= Britton
 |first= John Phillips
 |title= Ptolemy's Determination of the Obliquity of the Ecliptic
 |journal= [[Centaurus (journal)|Centaurus]]
 |date= Dec 1969
 |volume= 14
 |pages= 29–41
 |doi= 10.1111/j.1600-0498.1969.tb00132.x
 |url= https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1600-0498.1969.tb00132.x}} Reprinted as Chapter 1 of.{{sfn|Britton|1992}}
* {{Cite journal
 |last1= Dambis
 |first1= A. K.
 |last2= Efremov
 |first2= Yu. N.
 |date= 2000
 |title= Dating Ptolemy's Star Catalogue through Proper Motions: The Hipparchan Epoch
 |journal= [[Journal for the History of Astronomy]]
 |volume= 31 |issue= 2
 |pages= 115–134
 |doi= 10.1177/002182860003100202
 |bibcode= 2000JHA....31..115D
 }}
* {{Cite journal
 |last= Dreyer
 |first= J. L. E.
 |date= 1917
 |title= On the Origin of Ptolemy's Catalogue of Stars
 |journal= [[Monthly Notices of the Royal Astronomical Society]]
 |volume= 77
 |issue= 7
 |page= 528
 |doi= 10.1093/mnras/77.7.528
 |doi-access= free
 |oclc= 10340650
}}
* {{cite journal
 |last= Gingerich
 |first= Owen
 |author-link= Owen Gingerich
 |date= 1980
 |title= Was Ptolemy a Fraud?
 |journal= Quarterly Journal of the Royal Astronomical Society
 |volume= 21
 |page= 253
 |bibcode= 1980QJRAS..21..253G
 |url= https://adsabs.harvard.edu/full/1980QJRAS..21..253G
}}
*{{cite journal
 |last= Gingerich
 |first= Owen
 |date= 1981 
 |title= Ptolemy Revisited - Reply to R.R. Newton
 |journal= Quarterly Journal of the Royal Astronomical Society
 |volume= 22
 |pages= 40–44
 |url= https://articles.adsabs.harvard.edu/pdf/1981QJRAS..22...40G
}}
* {{cite journal
 |last= Goldstein
 |first= Bernard R.
 |author-link= Bernard R. Goldstein
 |date= 24 February 1978
 |title= Casting Doubt on Ptolemy: The Crime of Claudius Ptolemy. Robert R. Newton.
 |journal= Science
 |volume= 199
 |issue= 4331
 |pages= 872–873
 |doi= 10.1126/science.199.4331.872.a
 |pmid= 17757580
}}
* {{Cite journal
 |last= Hoffmann
 |first= Susanne M.
 |date= 2018
 |title= The Genesis of Hipparchus' Celestial Globe
 |journal= Mediterranean Archaeology and Archaeometry
 |volume= 18
 |issue= 4
 |pages= 281–287
 |doi= 10.5281/ZENODO.1477980
 |doi-access= free
}}
* {{cite journal
 |last= Kunitzsch
 |first= Paul
 |date= 1986
 |title= The Star Catalogue Commonly Appended to the Alfonsine Tables
 |journal= Journal for the History of Astronomy
 |volume= 17
 |number= 49
 |pages= 89–98
 |doi= 10.1177/002182868601700202
 |bibcode= 1986JHA....17...89K
 |bibcode-access= free
 |url= https://articles.adsabs.harvard.edu/pdf/1986JHA....17...89K
 |quote= Gerard of Cremona's Latin translation made in Toledo about 1175 from the Arabic, ...
}}
* {{cite journal
 |last= Lewis
 |first= H. A. G.
 |date= 1979
 |title= Review of ''The Crime of Claudius Ptolemy'', by R. R. Newton
 |journal= Imago Mundi
 |volume= 31
 |pages= 105–107
 |doi= 10.1080/03085697908592494
 |jstor= 1150735
}}
* {{Cite journal
 |last= Vogt
 |first= H.
 |date= 1925
 |title= Versuch einer Wiederherstellung von Hipparchs Fixsternverzeichnis
 |trans-title= Attempting a restoration of Hipparchus' fixed-star catalog
 |language= de
 |journal= [[Astronomische Nachrichten]]
 |volume= 224
 |issue= 2–3
 |pages= 17–54 
 |doi= 10.1002/asna.19252240202
 |bibcode= 1925AN....224...17V
}}
* {{cite journal
 |last= Wade
 |first= Nicholas
 |author-link= Nicholas Wade
 |date= 1977
 |title= Scandal in the Heavens: Renowned Astronomer Accused of Fraud
 |journal= Science
 |volume= 198
 |issue= 4318
 |pages= 707–709
 |doi= 10.1126/science.198.4318.707
 |bibcode= 1977Sci...198..707W
}}
{{refend}}

====Websites====
{{refbegin}}
* {{Cite web 
 |last= Jodra
 |first= Serge
 |date= 2013
 |title= L'Almageste
 |language= fr
 |edition= Online
 |url= https://www.cosmovisions.com/textAlmageste.htm
 |website= cosmovisions.com
 |via= Imago Mundi
}}
* {{Cite web
 |last= Ridpath
 |first= Ian
 |author-link= Ian Ridpath
 |date= 2023 
 |title= Star Tales – Ptolemy's Almagest
 |edition= Revised, online
 |url= http://www.ianridpath.com/startales/almagest.html
 |website= ianridpath.com
}}
{{refend}}

== Further reading ==
* {{cite book
 |last= Evans
 |first= James
 |date= 1998
 |title= The History and Practice of Ancient Astronomy
 |publisher = [[Oxford University Press]]
 |isbn = 978-0-19-509539-5
}}
*{{cite journal
 |last1=Neugebauer
 |first1=Otto
 |author-link= Otto Neugebauer
 |date= 1948
 |title= Mathematical Methods in Ancient Astronomy
 |journal= Bulletin of the American Mathematical Society
 |volume= 54
 |issue= 11
 |pages= 1013–1041
 |doi= 10.1090/S0002-9904-1948-09089-9
 |doi-access= free
}}
* {{cite book
 |last= Neugebauer
 |first= Otto
 |author-link= Otto Neugebauer
 |date= 1975
 |title= A History of Ancient Mathematical Astronomy
 |at= [https://archive.org/details/historyofancient0000neug/ Part 1], [https://archive.org/details/historyofancient0000neug_v8q1 Part 2], [https://archive.org/details/historyofancient0000neug_z6r9 Part 3]
 |location= Berlin
 |publisher= Springer
 |isbn= 3-540-06995-X
}}
*{{cite journal
 |last=Hanson
 |first = Norwood Russell
 |date= 1960
 |title= The Mathematical Power of Epicyclical Astronomy
 |journal= Isis
 |volume= 51
 |issue= 2
 |pages= 150–158
 |doi= 10.1086/348869
 |jstor= 226846
}}
* {{Cite book
 |last= Ridpath
 |first= Ian
 |author-link= Ian Ridpath 
 |date= 2018
 |orig-date= 1998
 |title= Star Tales
 |edition= Rev.
 |location= Cambridge
 |publisher= [[Lutterworth Press]]
 |isbn= 978-0-7188-9478-8
}}
* {{cite book
 |last= Pedersen
 |first= Olaf
 |author-link= Olaf Pedersen 
 |date= 1993
 |orig-date= 1974
 |title= Early Physics and Astronomy: A Historical Introduction
 |edition= 2nd
 |publisher= Cambridge University Press
 |isbn= 978-0-521-40899-8
}}
* {{cite book
 |last= Pedersen
 |first= Olaf
 |date= 2011
 |orig-date= 1974
 |title= A Survey of the Almagest
 |edition= 2nd
 |location= Berlin
 |publisher= Springer
 |isbn= 978-1-4939-3922-0
}}
* {{cite book
 |last= Ptolemaeus
 |first= Claudius
 |author-link= Ptolemy
 |title= Syntaxis mathematica
 |language= el
 |url= https://www.digitale-sammlungen.de/de/view/bsb00066523?page=,1
 |oclc= 767751182
 |access-date= 10 April 2023
 |via= MDZ/München, Bayerische Staatsbibliothek
}}
* {{cite journal
 |last= Shank
 |first= Michael H.
 |date= 2009
 |title= ''Islamic Science and the Making of European Renaissance'' by George Saliba
 |type= Book review
 |journal= Aestimatio
 |volume= 6
 |pages= 63–72
 |url= https://ircps.org/aestimatio-archive/2009-volume-6/aestimatio-6-59-62/
}}

== External links ==
{{commons category}}
* [https://www.wilbourhall.org/pdfs/HeibergAlmagestComplete.pdf Syntaxis Mathematica] (Almagest), original Greek, edited by [[Johan Ludvig Heiberg (historian)|Johan Ludvig Heiberg]], 1898.
* [https://catalog.hathitrust.org/Record/000557831 Syntaxis mathematica in J.L. Heiberg's edition (1898–1903)]
* [https://www.wilbourhall.org/pdfs/analemma.pdf Ptolemy's ''De Analemmate''. PDF scans of Heiberg's Greek edition, now in the public domain] (Koine Greek)
* [https://classicalliberalarts.com/resources/PTOLEMY_ALMAGEST_ENGLISH.pdf Toomer's English translation] Duckworth, 1984.
* [https://find.slv.vic.gov.au/discovery/fulldisplay?docid=alma994851543607636&context=L&vid=61SLV_INST:SLV&lang=en&search_scope=slv_local&adaptor=Local%20Search%20Engine&tab=searchProfile&query=any,contains,Almagest&offset=0 Ptolemy. ''Almagest''.] Latin translation from the Arabic by [[Gerard of Cremona]]. Digitized version of manuscript made in Northern Italy c. 1200–1225 held by the [[State Library of Victoria]].
* [http://www.univie.ac.at/hwastro/rare/1515_ptolemae.htm University of Vienna: ''Almagestum'' (1515)] PDFs of different resolutions. Edition of Petrus Liechtenstein, Latin translation of [[Gerard of Cremona]].
* [https://webspace.science.uu.nl/~gent0113/astro/almagestephemeris.htm Almagest Ephemeris Calculator] by Robert Van Gent. Positions for any date, translation of dates in calendars used by Ptolemy. Extensive list of references and articles.
* [https://webspace.science.uu.nl/~gent0113/astro/ancientephemerides.htm Online luni-solar and planetary ephemeris calculator based on the ''Almagest'']
* [https://web.archive.org/web/20100618052417/http://astrotalkuk.org/2010/01/29/episode-33-january-27th-2010-ptolemy%E2%80%99s-almagest/ A podcast discussion by Prof. M Heath and Dr A. Chapman of a recent re-discovery of a 14th-century manuscript in the university of Leeds Library]
* [https://web.archive.org/web/20071115020105/http://astro.isi.edu/reference/almagest.html Star catalog] in [[ASCII]] {{in lang|la}}
* [https://www.youtube.com/watch?v=Plxed3JVOnI Animation of Ptolemy's model of the universe] by Andre Rehak (YouTube)
* {{in lang|fr}} [https://ecliptiqc.ca/Almageste.php French translation, with some diagrams animated, interactive, or random]
* {{in lang|he}} [https://he.wikisource.org/w/index.php?title=ביאור:מעומד/רבנית/ראשונים/רמבם/משנה/הקדמות/זרעים Maimonides explaining why you need to learn Almagest first to understand science]
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{{Greek mathematics}}
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[[Category:Ancient Greek astronomical works]]
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