Claudius Ptolemy in the context of Jacobus Angelus

The Harmonia Macrocosmica is a star atlas written by Andreas Cellarius and published in 1660 by Johannes Janssonius. The first part of the atlas contains copper plate prints depicting the world systems of Claudius Ptolemy, Nicolaus Copernicus, and Tycho Brahe. At the end are star maps of the classical and further constellations, the latter ones as introduced by Julius Schiller in his Coelum stellatum christianum of 1627.

For its importance in the history of cartography, particularly of celestial cartography, the Harmonia Macrocosmica is considered one of the notable masterworks from the Golden Age of Dutch/Netherlandish cartography (c. 1570s–1670s), along with Abraham Ortelius's Theatrum Orbis Terrarum and Johannes Blaeu's Atlas Maior. It is often described as the most beautiful celestial atlas ever published.

Geography (from Ancient Greek γεωγραφία geōgraphía; combining gê 'Earth' and gráphō 'write', literally 'Earth writing') is the study of the lands, features, inhabitants, and phenomena of Earth. Geography is an all-encompassing discipline that seeks an understanding of Earth and its human and natural complexities—not merely where objects are, but also how they have changed and come to be. While geography is specific to Earth, many concepts can be applied more broadly to other celestial bodies in the field of planetary science. Geography has been called "a bridge between natural science and social science disciplines."

The history of geography as a discipline spans cultures and millennia, being independently developed by multiple groups, and cross-pollinated by trade between these groups. Geography as a discipline dates back to the earliest attempts to understand the world spatially, with the earliest example of an attempted world map dating to the 9th century BCE in ancient Babylon. Origins of many of the concepts in geography can be traced to Greek Eratosthenes of Cyrene, who may have coined the term "geographia" (c. 276 BC – c. 195/194 BC). The first recorded use of the word γεωγραφία was as the title of a book by Greek scholar Claudius Ptolemy (100 – 170 AD). During the Middle Ages, geography was influenced by Islamic scholars, like Muhammad al-Idrisi, producing detailed maps of the world. The Age of Discovery was influential in the development of geography, as European explorers mapped the New World. Modern developments include the development of geomatics and geographic information science.

The Geography (Ancient Greek: Γεωγραφικὴ Ὑφήγησις, Geōgraphikḕ Hyphḗgēsis, lit. "Geographical Guidance"), also known by its Latin names as the Geographia and the Cosmographia, is a gazetteer, an atlas, and a treatise on cartography, compiling the geographical knowledge of the 2nd-century Roman Empire. Originally written by Claudius Ptolemy in Greek at Alexandria around 150 AD, the work was a revision of a now-lost atlas by Marinus of Tyre using additional Roman and Persian gazetteers and new principles.

Its translation into Arabic by al-Khwarismi in the 9th century was highly influential on the geographical knowledge and cartographic traditions of the Islamic world. Alongside the works of Islamic scholars—and the commentary containing revised and more accurate data by Alfraganus—Ptolemy's work was subsequently highly influential on Medieval and Renaissance Europe.

Agathodaemon of Alexandria (Ancient Greek: Ἀγαθοδαίμων Ἀλεξανδρεὺς, Agathodaímōn Alexandreùs) was a Greek or Hellenized Egyptian cartographer, presumably from Alexandria, Roman Egypt, during late Antiquity, likely in the 2nd century AD.

Agathodaemon is mentioned in some of the earliest manuscripts of Ptolemy's Geography:

The Canon of Kings was a dated list of kings used by ancient astronomers as a convenient means to date astronomical phenomena, such as eclipses. For a period, the Canon was preserved by the astronomer Claudius Ptolemy, and is thus known sometimes as Ptolemy's Canon. It is one of the most important bases for modern knowledge of ancient chronology.

The Canon derives originally from Babylonian sources. Thus, it lists Kings of Babylon from 747 BC until the conquest of Babylon by Achaemenid Persians in 539 BC, and then Persian kings from 538 to 332 BC. At this point, the Canon was continued by Greek astronomers in Alexandria, and lists the Macedonian kings from 331 to 305 BC, the Ptolemies from 304 BC to 30 BC, and the Roman and Byzantine Emperors, although they are not kings; in some manuscripts the list is continued down to the Fall of Constantinople in 1453.

The Khuni, Huni or Chuni were a people of the North Caucasus during late antiquity. They have sometimes been referred to as the North Caucasian Huns and are often assumed to be related to the Huns who later entered Eastern Europe. However, the ethnolinguistic and geographical origins of the Khuni are unclear.

The first contemporaneous reference to the Khuni may be by Dionysius Periegetes and Claudius Ptolemy's Geography, in the 2nd century CE, when they are said to be living near the Caspian Sea.

Marinus of Tyre (Ancient Greek: Μαρῖνος ὁ Τύριος, Marînos ho Týrios; c. AD 70–130) was a geographer, cartographer and mathematician, who founded mathematical geography and provided the underpinnings of Claudius Ptolemy's influential Geography.

The Agri Decumates or Decumates Agri ("Decumatian Fields") were a region of the Roman Empire's provinces of Germania Superior and Raetia, covering the Black Forest, Swabian Jura, and Franconian Jura areas between the Rhine, Main, and Danube rivers, in present southwestern Germany, including present Frankfurt, Stuttgart, Freiburg im Breisgau, and Weißenburg in Bayern.

The only ancient reference to the name comes from Tacitus' book Germania (chapter 29). However, the later geographer Claudius Ptolemy does mention "the desert of the Helvetians" in this area.

The Semnones were a Germanic people, and more specifically a Suebi people, who lived near the Elbe river in the 1st and 2nd centuries AD, during the time of the Roman empire.

The 2nd century geographer Claudius Ptolemy places the Semnones between the Elbe and "Suebos" river. Modern scholars believe that the Suebos was the Oder. However, archaeological evidence suggests they stretched as far as the Spree and Havel rivers in the east, and not quite as far as the Oder. To their north was another part of the Havel, and to the south the Fläming Heath. In present day terms they were therefore in the area between the modern cities of Magdeburg and Berlin.

Plato Tiburtinus (Latin: Plato Tiburtinus, "Plato of Tivoli"; fl. 12th century) was a 12th-century Italian mathematician, astronomer and translator who lived in Barcelona from 1116 to 1138. He is best known for translating Hebrew and Arabic documents into Latin, and was apparently the first to translate information on the astrolabe (an astronomical instrument) from Arabic.

Plato of Tivoli translated the Arab astrologer Albohali's "Book of Birth" into Latin in 1136. He translated Claudius Ptolemy's Tetrabiblos from Arabic to Latin in 1138, the astronomical works of al-Battani, Theodosius' Spherics and the Liber Embadorum by Abraham bar Chiia.He has worked together with the Jewish mathematician Savasorda (Abraham Bar Ḥiyya Ha-Nasi). His manuscripts were widely circulated and were among others used by Albertus Magnus and Fibonacci.

Equant (or punctum aequans) is a mathematical concept developed by Claudius Ptolemy in the 2nd century AD to account for the observed motion of the planets. The equant is used to explain the observed speed change in different stages of the planetary orbit. This planetary concept allowed Ptolemy to keep the theory of uniform circular motion alive by stating that the path of heavenly bodies was uniform around one point and circular around another point.

Ptolemy does not have a word for the equant – he used expressions such as "the eccentre producing the mean motion".

Ancient Aethiopia, (Greek: Αἰθιοπία, romanized: Aithiopía) first appears as a geographical term in classical documents in reference to the skin color of the inhabitants of the upper Nile in Sudan, areas south of the Sahara, and less often to certain parts of Asia. Its earliest mention is in the works of Homer: twice in the Iliad, and three times in the Odyssey. The Greek historian Herodotus uses the appellation to refer to regions south of Egypt when describing "Aethiopians," most commonly Nubia. Likewise, the Hebrew term Cushi is derived from Kushite. Despite this, the Byzantine Greeks also referred to the Aksumites as Ethiopians and Negus Ezana, conqueror of Meroë took on the title of "king of Ethiopia" prior to the rise of the medieval Ethiopian Empire. The ancient Libyans (North African Berbers) were also called White Aethiopians by contemporary Greek sources. By the modern period the term Aethiopian Sea was used to refer to the southern Atlantic ocean, particularly the area adjacent to West Africa.

Though near universally used to invoke the "Ethiopia of North Africa" ("African Ethiopia"); there was another region sometimes called Asiatic Ethiopia, located either in one of the provinces of Mesopotamia (Assyria and Babylon), or in Ancient Armenia (Colchis). Ethiopia in Roman History (1-200 AD) states later the term "Ethiopia" would become synonymous with all Africans. Unlike the earlier Greek writers who distinguished Ethiopians from other Africans, Claudius Ptolemy (90–168 AD), a Roman citizen who lived in Alexandria, used "Ethiopia" as a racial term. In his Tetrabiblos: Or Quadripartite, he tried to explain the physical characteristics of people around the world saying, 'They are consequently black in complexion, and have thick and curled hair...and they are called by the common name of Aethiopians.'" The Classical Greek historian wrote about a colony founded in the region of Colchis, which was inhabited by Ethiopic people, believed to have been brought there by the Egyptian Pharaoh Sesostris. Herodotus states that the Colchians, with the Ancient Egyptians and the Ethiopians, were the first to practice circumcision, a custom which he claims that the Colchians inherited from remnants of the army of Pharaoh Sesostris (Senusret III). Herodotus writes:

The Hermunduri, Hermanduri, Hermunduli, Hermonduri, or Hermonduli were an ancient Germanic tribe, who occupied an inland area near the source of the Elbe river, around what is now Bohemia from the first to the third century, though they have also been speculatively associate with Thuringia further north. According to an old proposal based on the similarity of the names, the Thuringii may have been the descendants of the Hermunduri. At times, they apparently moved to the Danube frontier with Rome. Claudius Ptolemy mentions neither tribe in his geography but instead the Teuriochaemae, who may also be connected to both.