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An ASTROLABE (Greek : ἀστρολάβος _astrolabos_; Arabic
Arabic
: ٱلأَسْطُرلاب‎‎‎‎ _al-Asturlāb_) is an elaborate inclinometer , historically used by astronomers and navigators , to measure the inclined position in the sky of a celestial body , day or night. It can thus be used to identify stars or planets, to determine local latitude given local time and vice versa, to survey, or to triangulate . It was used in classical antiquity , the Islamic Golden Age , the European Middle Ages
Middle Ages
and the Renaissance
Renaissance
for all these purposes.

While the astrolabe is effective for determining latitude on land or calm seas, it is less reliable on the heaving deck of a ship in rough seas. The mariner\'s astrolabe was developed to solve that problem.

CONTENTS

* 1 Etymology

* 2 History

* 2.1 Ancient world * 2.2 Medieval era * 2.3 Astrolabes and clocks

* 3 Construction * 4 See also * 5 References * 6 External links

ETYMOLOGY

OED gives the translation "star-taker" for the English word "astrolabe" and traces it, through medieval Latin, to the Greek word _astrolabos_ from _astron_ "star" and _lambanein_ "to take". In the medieval Islamic world the Arabic
Arabic
word _"al-Asturlāb"_ (i.e. astrolabe) was given various etymologies. In Arabic
Arabic
texts, the word is translated as _"ākhdhu al-Nujuum"_ ( Arabic
Arabic
: آخِذُ ٱلنُّجُومْ‎‎, lit. "star-taker"), a direct translation of the Greek word.

Al-Biruni quotes and criticizes the medieval scientist Hamzah al-Isfahani who had stated: "asturlab is an arabization of this Persian phrase" (_sitara yab_, meaning "taker of the stars"). In medieval Islamic sources, there is also a "fictional" and popular etymology of the words as "lines of lab". In this popular etymology , "Lab" is a certain son of Idris (=Enoch). This etymology is mentioned by a 10th-century scientist named al-Qummi but rejected by al-Khwarizmi .

HISTORY

ANCIENT WORLD

An early astrolabe was invented in the Hellenistic world by Apollonius of Perga , around 220 BC or in 150 BC and is often attributed to Hipparchus
Hipparchus
. A marriage of the planisphere and dioptra , the astrolabe was effectively an analog calculator capable of working out several different kinds of problems in spherical astronomy. Theon of Alexandria (c. 335 – c. 405) wrote a detailed treatise on the astrolabe, and Lewis argues that Ptolemy
Ptolemy
used an astrolabe to make the astronomical observations recorded in the _ Tetrabiblos
Tetrabiblos
_. Some historians attribute the astrolabe's invention to Hypatia , the daughter of Theon of Alexandria, noting that Synesius, a student of Hypatia, credits her for the invention in his letters.

Astrolabes continued in use in the Greek -speaking world throughout the Byzantine period. About 550 AD the Christian philosopher John Philoponus wrote a treatise on the astrolabe in Greek, which is the earliest extant Greek treatise on the instrument. In addition, Severus Sebokht , a bishop who lived in Mesopotamia, also wrote a treatise on the astrolabe in Syriac in the mid-7th century. Severus Sebokht refers in the introduction of his treatise to the astrolabe as being made of brass, indicating that metal astrolabes were known in the Christian East well before they were developed in the Islamic world or the Latin West.

MEDIEVAL ERA

A treatise explaining the importance of the astrolabe by Nasir al-Din al-Tusi , Persian scientist. Astrolabe
Astrolabe
of Jean Fusoris (fr), made in Paris
Paris
, 1400 An 18th-century Persian astrolabe Disassembled 18th-century astrolabe Exploded view of an astrolabe Animation showing how celestial and geographic coordinates are mapped on an astrolabe's tympan through a stereographic projection. Hypothetical tympan (40 degrees North Latitude) of a 16th-century European planispheric astrolabe.

Astrolabes were further developed in the medieval Islamic world , where Muslim astronomers introduced angular scales to the astrolabe, adding circles indicating azimuths on the horizon . It was widely used throughout the Muslim world, chiefly as an aid to navigation and as a way of finding the Qibla
Qibla
, the direction of Mecca
Mecca
. The first person credited with building the astrolabe in the Islamic world is reportedly the 8th-century mathematician Muhammad al-Fazari .

The mathematical background was established by the Muslim astronomer Albatenius in his treatise _Kitab az-Zij_ (c. 920 AD), which was translated into Latin by Plato Tiburtinus (_De Motu Stellarum_). The earliest surviving dated astrolabe is dated AH 315 (927–8 AD). In the Islamic world, astrolabes were used to find the times of sunrise and the rising of fixed stars, to help schedule morning prayers (salat ). In the 10th century, al-Sufi first described over 1,000 different uses of an astrolabe, in areas as diverse as astronomy , astrology , navigation , surveying , timekeeping , prayer , Salat
Salat
, Qibla
Qibla
, etc. Astrolabium Masha'Allah Public Library Bruges (nl) Ms. 522

The spherical astrolabe , a variation of both the astrolabe and the armillary sphere , was invented during the Middle Ages
Middle Ages
by astronomers and inventors in the Islamic world. The earliest description of the spherical astrolabe dates back to Al-Nayrizi (fl. 892–902). In the 12th century, Sharaf al-Dīn al-Tūsī invented the _linear astrolabe_, sometimes called the "staff of al-Tusi", which was "a simple wooden rod with graduated markings but without sights. It was furnished with a plumb line and a double chord for making angular measurements and bore a perforated pointer". The first geared mechanical astrolabe was later invented by Abi Bakr of Isfahan
Isfahan
in 1235.

Peter of Maricourt , in the last half of the 13th century, also wrote a treatise on the construction and use of a universal astrolabe (_Nova compositio astrolabii particularis_). Universal astrolabes can be found at the History of Science Museum in Oxford.

The English author Geoffrey Chaucer (c. 1343–1400) compiled a treatise on the astrolabe for his son, mainly based on Messahalla . The same source was translated by the French astronomer and astrologer Pélerin de Prusse and others. The first printed book on the astrolabe was _Composition and Use of Astrolabe_ by Christian of Prachatice , also using Messahalla, but relatively original.

In 1370, the first Indian treatise on the astrolabe was written by the Jain astronomer Mahendra Suri .

The first known metal astrolabe in Western Europe is the Destombes astrolabe made from brass in tenth-century Spain. Metal astrolabes avoided the warping that large wooden astrolabes were prone to, allowing the construction of larger and therefore more accurate instruments. Metal astrolabes were also heavier than wooden instruments of the same size, making it difficult to use them as navigational instruments.

The astrolabe was almost certainly first brought north of the Pyrenees by Gerbert of Aurillac (future Pope Sylvester II ), where it was integrated into the quadrivium at the school in Reims, France, sometime before the turn of the 11th century. In the 15th century, the French instrument-maker Jean Fusoris (fr) (c. 1365–1436) also started remaking and selling astrolabes in his shop in Paris
Paris
, along with portable sundials and other popular scientific devices of the day. Thirteen of his astrolabes survive to this day. One more special example of craftsmanship in the early 15th-century Europe is the astrolabe dated 1420, designed by Antonius de Pacento and made by Dominicus de Lanzano.

In the 16th century, Johannes Stöffler published _Elucidatio fabricae ususque astrolabii_, a manual of the construction and use of the astrolabe. Four identical 16th-century astrolabes made by Georg Hartmann provide some of the earliest evidence for batch production by division of labor .

ASTROLABES AND CLOCKS

At first mechanical astronomical clocks were influenced by the astrolabe; in many ways they could be seen as clockwork astrolabes designed to produce a continual display of the current position of the sun, stars, and planets. For example, Richard of Wallingford
Richard of Wallingford
's clock (c. 1330) consisted essentially of a star map rotating behind a fixed rete, similar to that of an astrolabe.

Many astronomical clocks, such as the famous clock at Prague , use an astrolabe-style display, adopting a stereographic projection (see below) of the ecliptic plane.

In recent times, astrolabe watches have become a feature of haute horologie. For example, in 1985 Swiss watchmaker Dr. Ludwig Oechslin designed and built an astrolabe wristwatch in conjunction with Ulysse Nardin . Dutch watchmaker Christaan van der Klauuw also manufactures astrolabe watches today.

CONSTRUCTION

The Hartmann astrolabe in Yale collection. This instrument shows its rete and rule. Celestial Globe, Isfahan
Isfahan
(?), Iran 1144. Shown at the Louvre Museum , this globe is the third oldest surviving in the world. Computer-generated planispheric astrolabe

An astrolabe consists of a disk, called the _mater_ (mother), which is deep enough to hold one or more flat plates called _tympans_, or _climates _. A tympan is made for a specific latitude and is engraved with a stereographic projection of circles denoting azimuth and altitude and representing the portion of the celestial sphere above the local horizon. The rim of the mater is typically graduated into hours of time , degrees of arc , or both.

Above the mater and tympan, the _rete_, a framework bearing a projection of the ecliptic plane and several pointers indicating the positions of the brightest stars , is free to rotate. These pointers are often just simple points, but depending on the skill of the craftsman can be very elaborate and artistic. There are examples of astrolabes with artistic pointers in the shape of balls, stars, snakes, hands, dogs' heads, and leaves, among others. The names of the indicated stars were often engraved on the pointers in Arabic
Arabic
or Latin. Some astrolabes have a narrow _rule _ or _label_ which rotates over the rete, and may be marked with a scale of declinations .

The rete, representing the sky , functions as a star chart . When it is rotated, the stars and the ecliptic move over the projection of the coordinates on the tympan. One complete rotation corresponds to the passage of a day. The astrolabe is therefore a predecessor of the modern planisphere .

On the back of the mater there is often engraved a number of scales that are useful in the astrolabe's various applications. These vary from designer to designer, but might include curves for time conversions, a calendar for converting the day of the month to the sun's position on the ecliptic, trigonometric scales, and a graduation of 360 degrees around the back edge. The _alidade _ is attached to the back face. An alidade can be seen in the lower right illustration of the Persian astrolabe above. When the astrolabe is held vertically, the alidade can be rotated and the sun or a star sighted along its length, so that its altitude in degrees can be read ("taken") from the graduated edge of the astrolabe; hence the word's Greek roots: "astron" (ἄστρον) = star + "lab-" (λαβ-) = to take.

SEE ALSO

* Antikythera mechanism * Armillary sphere
Armillary sphere
* Astrarium * AstroLabs – a company named after the astrolabe * Astronomical clock
Astronomical clock
* Canterbury Astrolabe Quadrant * Cosmolabe * Equatorium * Hypatia * Islamic astronomy * Marshall Islands stick chart * Nocturnal * Orrery * Philippe Danfrie , designer and maker of mathematical instruments , globes and astrolabes * Planetarium
Planetarium
* Planisphere * Prague Orloj * Sextant (astronomical) * Sharafeddin Tusi , the inventor of the linear astrolabe * Torquetum

REFERENCES

Footnotes

* ^ Modern editions of John Philoponus ' treatise on the astrolabe are _De usu astrolabii eiusque constructione libellus_ (On the Use and Construction of the Astrolabe), ed. Heinrich Hase, Bonn: E. Weber, 1839, OCLC
OCLC
165707441 (or id. Rheinisches Museum für Philologie 6 (1839): 127–71); repr. and translated into French by Alain Philippe Segonds, _Jean Philopon, traité de l'astrolabe,_ Paris: Librairie Alain Brieux, 1981, OCLC
OCLC
10467740 ; and translated into English by H.W. Green in R.T. Gunther, _The Astrolabes of the World_, Vol. 1/2, Oxford, 1932, OL 18840299M repr. London: Holland Press, 1976, OL 14132393M pp. 61–81.

* ^ O\'Leary, De Lacy (1948). _How Greek Science passed to the Arabs_. Routledge and Kegan Paul. "The most distinguished Syriac scholar of this later period was Severus Sebokht (d. 666–7), Bishop of Kennesrin. In addition to these works he also wrote on astronomical subjects (Brit. Mus. Add. 14538), and composed a treatise on the astronomical instrument known as the astrolabe, which has been edited and published by F. Nau (Paris, 1899)." Severus' treatise was translated by Jessie Payne Smith Margoliouth in R.T. Gunther, _Astrolabes of the World_, Oxford, 1932, pp. 82–103. * ^ Savage-Smith, Emilie (1993). "Book Reviews". _Journal of Islamic Studies_. 4 (2): 296–299. doi :10.1093/jis/4.2.296 . There is no evidence for the Hellenistic origin of the spherical astrolabe, but rather evidence so far available suggests that it may have been an early but distinctly Islamic development with no Greek antecedents.

Notes

* ^ In the Islamic world, it was used to navigate deserts, then oceans, and to calculate the direction to Mecca
Mecca
. * ^ astrolabe, _Oxford English Dictionary_ 2nd ed. 1989 * ^ Astrolabe, on Oxford Dictionaries * ^ "Online Etymology Dictionary". Etymonline.com. Retrieved 2013-11-07. * ^ _A_ _B_ King 1981 , p. 44. * ^ King 1981 , p. 51. * ^ King 1981 , p. 45. * ^ Lewis 2001 . * ^ Michael Deakin (August 3, 1997). "Ockham's Razor: Hypatia of Alexandria". ABC Radio. Retrieved July 10, 2014. * ^ Krebs et al. * ^ Sebokht, Severus. "Description of the astrolabe". Tertullian.org. * ^ See p. 289 of Martin, L. C. (1923), " Surveying and navigational instruments from the historical standpoint", _Transactions of the Optical Society_, 24 (5): 289–303, Bibcode :1923TrOS...24..289M, ISSN 1475-4878 , doi :10.1088/1475-4878/24/5/302 . * ^ Victor J. Katz & Annette Imhausen (2007), _The Mathematics of Egypt, Mesopotamia, China, India, and Islam: a Sourcebook_, Princeton University Press , p. 519, ISBN 0-691-11485-4 * ^ Richard Nelson Frye : _Golden Age of Persia_. p. 163 * ^ "The Earliest Surviving Dated Astrolabe". _HistoryOfInformation.com_. * ^ Dr. Emily Winterburn ( National Maritime Museum
National Maritime Museum
), Using an Astrolabe, Foundation for Science Technology and Civilisation, 2005. * ^ Lachièz-Rey, Marc; Luminet, Jean-Pierre (2001). _Celestial Treasury: From the Music of Spheres to the Conquest of Space_. Trans. Joe Laredo. Cambridge, UK: Cambridge University Press. p. 74. ISBN 978-0-521-80040-2 . * ^ O\'Connor, John J. ; Robertson, Edmund F. , "Sharaf al-Din al-Muzaffar al-Tusi", _ MacTutor History of Mathematics archive _, University of St Andrews
University of St Andrews
. * ^ Bedini, Silvio A. ; Maddison, Francis R. (1966). "Mechanical Universe: The Astrarium of Giovanni de' Dondi". _Transactions of the American Philosophical Society_. 56 (5): 1–69. JSTOR 1006002 . doi :10.2307/1006002 . * ^ Glick, Thomas; et al., eds. (2005), _Medieval Science, Technology, and Medicine: An Encyclopedia_, Routledge, p. 464, ISBN 0-415-96930-1 * ^ "Qantara – \'Carolingian\' astrolabe". Qantara-med.org. Retrieved 2013-11-07. * ^ Nancy Marie Brown (2010), "The Abacus and the Cross". Page 140. Basic Books. ISBN 978-0-465-00950-3 * ^ Boyle, David (2011). _Toward the Setting Sun: Columbus, Cabot, Vespucci, and the Race for America_. Bloomsbury Publishing USA. p. 253. ISBN 9780802779786 . . * ^ Nancy Marie Brown (2010), "The Abacus and the Cross". Page 143. basic Books. ISBN 978-0-465-00950-3 * ^ Hockey, Thomas (2009). _The Biographical Encyclopedia of Astronomers_. Springer Publishing . ISBN 978-0-387-31022-0 . Retrieved August 22, 2012. * ^ Ralf Kern (2010), _Wissenschaftliche Instrumente in ihrer Zeit_. Band 1: Vom Astrolab zum mathematischen Besteck. Cologne, S. 204. ISBN 978-3-86560-865-9 * ^ North 2005 . * ^ Stephenson, Bruce; Bolt, Marvin; Friedman, Anna Felicity (2000). _The Universe
Universe
Unveiled: Instruments and Images through History_. Cambridge, UK: Cambridge University Press. pp. 108–109. ISBN 0-521-79143-X . * ^ Stephenson, Bruce; Bolt, Marvin; Friedman, Anna Felicity (2000). _The Universe
Universe
Unveiled: Instruments and Images through History_. Cambridge, UK: Cambridge University Press. pp. 108–109. ISBN 0-521-79143-X . * ^ " Star
Star
Names on Astrolabes". Ian Ridpath. Retrieved 2016-11-12.

Bibliography

* Evans, James (1998), _The History and Practice of Ancient Astronomy_, Oxford University Press, ISBN 0-19-509539-1 . * Gunella, Alessandro; Lamprey, John (2007), _Stoeffler's Elucidatio (translation of Elucidatio fabricae ususque astrolabii into English)_, John Lamprey * King, D. A (1981), "The Origin of the Astrolabe
Astrolabe
According to the Medieval Islamic Sources", _Journal for the History of Arabic Science_, 5: 43–83 * King, Henry (1978), _Geared to the Stars: the Evolution of Planetariums, Orreries, and Astronomical Clocks_, University of Toronto Press * Krebs, Robert E.; Krebs, Carolyn A. (2003), _Groundbreaking Scientific Experiments, Inventions, and Discoveries of the Ancient World_, Greenwood Press . * Laird, Edgar (1997), Carol Poster and Richard Utz, ed., "Astrolabes and the Construction of Time
Time
in the Late Middle Ages.", _Constructions of Time
Time
in the Late Middle Ages_, Evanston, IL: Northwestern University Press: 51–69 * Laird, Edgar; Fischer, Robert, eds. (1995), "Critical edition of Pélerin de Prusse on the Astrolabe
Astro