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O: Modern Western Constellations
26: Ptolemy's star catalogue
An imaginary portrait of the Greek astronomer (and Roman citizen) Claudius Ptolemy (life dates circa 85 CE - circa 165).
Greek manuscript of Ptolemy's Almagest in the Vatican Library. Dated to the 9th-century CE it is considered the oldest and most elegant of all the manuscripts of the Almagest. The pages show Book IV Chapter 2, on Hipparchus's examination of Babylonian cycles for the motion of the moon.
Claudius Ptolemy was born circa 85 CE in Egypt and died circa 165 in Alexandria in Egypt. He made his astronomical observations between circa 127 CE and 141 CE. Ptolemy was one of the most influential Greek astronomers and geographers of his time. However, very little is actually known of his life. His name, Claudius Ptolemy, combines a mix of the Greek Egyptian "Ptolemy" and the Roman "Claudius."
All of Ptolemy's major works have survived. The original Greek title of his most important work was The Mathematical Compilation (or The Great System of Astronomy) (but is now known by its popularised short Arabic title Almagest). The book was originally called Syntaxis by Ptolemy. Ptolemy's original Greek title was soon replaced by another Greek title The Greatest Compilation. Its commonly known title Almagest originates from its translation into Arabic as "al-majisti." (When Gherardo of Cremona translated the Arabic version of Ptolemy's work into Latin from the Arabic, in 1175, the al-Magisti become known as Almagest.) This thirteen book work, mostly concerned with presenting his original detailed geometric mathematical theory of the movements of the Sun, Moon, and planets, was his earliest and marks the high-point of Greek (Alexandrine) astronomy.
The earliest Western star catalogue (as we understand the term) originated with Ptolemy. The culmination of Greek establishment of constellation (and star) names was contained in (Book VII and Book VIII) of Ptolemy's Almagest written circa 140 CE. In it Ptolemy listed 1025 (fixed) stars. (The Almagest contained no star maps.) For his star catalogue Ptolemy used one system of coordinates (ecliptic longitudes and latitudes) for all the stars listed in it. Ptolemy did not identify the stars in his catalogue with Greek letters, as is done by modern astronomers. Each of the 1025 stars listed was identified (1) descriptively by its position within one of the 48 constellation figures; then (2) by its ecliptic latitude and longitude; and then (3) its magnitude. It is this particular star catalogue method of Ptolemy that enables us to identify, with considerable exactness, the boundaries (i.e., shape) of the ancient Greek constellations.
The constellation list in Ptolemy's star catalogue standardised the Western constellation scheme. The constellation scheme described by Ptolemy consisted of 21 northern constellations, 12 zodiacal constellations, and 15 southern constellations.
The northern constellations: (1) Little Bear, (2) Great Bear, (3) Dragon [Draco], (4) Cepheus, (5) Ploughman, (6) Northern Crown, (7) Kneeler [Hercules], (8) Lyre, (9) Bird [Cygnus], (10) Cassiopeia, (11) Perseus, (12) Charioteer (Auriga], (13) Serpent Holder, (14) Serpent [Serpens], (15) Arrow, (16) Eagle, (17) Dolphin, (18) Forepart of Horse [Equuleus], (19) Horse, (20) Andromeda, (21) Triangle.
The zodiacal constellations; (1) Ram, (2) Bull, (3) Twins, (4) Crab, (5) Lion, (6) Virgin, (7) Scales [Claws], (8) Scorpion, (9) Archer, (10) Goat-horned, (11) Water-pourer, (12) Fishes.
The southern constellations: (1) Sea-Monster [Whale], (2) Orion, (3) River, (4) Hare, (5) Dog [Greater Dog], (6) Dog's Forerunner [Lesser Dog], (7) Argo, (8) Watersnake, (9) Bowl, (10) Raven, (11) Centaur, (12) Beast [Wolf], (13) Censer [Altar], (14) Southern Crown, (15) Southern Fish.
Ptolemy's Almagest, and its star catalogue, became dominant and influential for many centuries both in the Islamic world and in Western Europe. Classical science declined after the fall of Rome and science generally ceased to exist in Western Europe. Greek astronomy ended with the Arab conquest of Alexandria in 641 CE. However, the Arab-Islamic world kept classical knowledge alive by translating Hellenistic scientific texts into Arabic. The late 8th-century and the 9th-century saw a growing interest in Greek science in the Islamic world. At the end of the 8th-century a flourishing astronomical science had developed in the Arab-Islamic world. The Abbasid Caliph al-Ma'mūn initiated the heyday of the sciences in the Arab-Islamic world, first in Damascus and then later in Baghdad. (He specifically established a House of Wisdom in Baghdad.) In the 9th-century CE the Abbasid caliphs at Baghdad commissioned the translation from Greek into Arabic of a number of scholarly manuscripts. By the 8th-century the centre of astronomy had moved from Alexandria to Baghdad where Greek astronomical works were translated into Arabic (the scientific language of the Arab-Islamic world). Ptolemy's Almagest was first translated into Syriac and then into Arabic. (In the early centuries of the Christian Era the Christian sects (Nestorians, Monophysites, etc.) comprising the Middle Eastern churches began to hold doctrines that diverged from the doctrines of the churches established in Rome (Catholic) and Constantinople (Byzantium). The Nestorians in particular not only translated Greek religious texts into Syriac but also Greek philosophical, mathematical, and scientific treatises. Due to persecution by the Orthodox Church many Nestorians and some Monophysites migrated to the Persian Empire in Mesopotamia and Iran. There they established schools of intellectual and scholarly discussion, including translation and commentary of Greek texts in Syriac.)
The main transmission of Greek thought to the Arabs was made through the medium of the Syriac manuscripts produced by the great Nestorian school established at Jundishapur in Khuzistan (southwest Persia). It became the leading intellectual centre where writing in Greek and Sanskrit were translated into Syriac and Pahlawi. (The Nestorian sect of Christians was founded in 428 CE by Nestorius, patriarch of Constantinople (who settled in Persia under the Sasanian dynasty).) When the Islamic Arabs conquered Persia this knowledge became available in Arabic.
The earliest translations of the Almagest into Arabic are known to date to circa 800 CE. (Ptolemy's book on mathematical astronomy was translated twice into Arabic in the 9th-century CE.) In the period after circa 1500 CE Arab-Islamic astronomy declined. In the 10th-century CE the power and patronage of the Baghdad caliphs began to decline, but Islamic astronomy continued to make advances in other parts of Islam. By the 11th-century the Baghdad Caliphate had lost control over much of its empire and weaker Caliphs were less inclined to encourage and finance scientific scholarship. The House of Wisdom and its library was destroyed in 1258 CE when the Mongol army ransacked Baghdad.
All knowledge of Ptolemy's Almagest was lost to Western Europe by the early middle ages. Until its decline in the 5th-century CE the city of Alexandria (in Egypt) was the centre of influence for Ptolemaic astronomy and texts. However, Ptolemy's Almagest in the original Greek continued to be copied and studied in the eastern (Byzantine) empire. In the 12th-century Spain became the conduit for the transmission of astronomical knowledge back into medieval Europe. This included the reintroduction of Ptolemy's works and additional Arab-Islamic astronomical texts.
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