Editing Astrolabe

{{Short description|Astronomical instrument}}
{{Hatnote group|
{{For|other pages with a similar name|Astrolabe (disambiguation)}}
{{Distinguish|Cosmolabe}}
}}{{use dmy dates|date=November 2024}}
[[File:Khalili Collection Islamic Art sci 0430 back.jpg|alt=Planispheric Astrolabe made of brass, cast, with fretwork rete and surface engraving|thumb|upright=1.2|North African, {{nobr|9th century {{sc|ce}},}} planispheric astrolabe. [[Khalili Collections|Khalili Collection]].]]
[[File:Iranian Astrolabe 14.jpg|thumb|A modern astrolabe made in 2013, in [[Tabriz]], Iran.|upright=1.2]]

An '''astrolabe''' ({{langx|grc|{{wikt-lang|grc|ἀστρολάβος}}|{{grc-transl|ἀστρολάβος}}|star-taker}}; {{langx|ar|ٱلأَسْطُرلاب|al-Asṭurlāb}}; {{langx|fa|ستاره‌یاب|Setāreyāb}}) is an [[astronomy|astronomical]] [[list of astronomical instruments|instrument]] dating to ancient times. It serves as a [[star chart]] and [[Model#Physical model|physical model]] of the visible [[celestial sphere|half-dome of the sky]]. Its various functions also make it an elaborate [[inclinometer]] and an [[analog computer|analog calculation device]] capable of working out several kinds of problems in astronomy. In its simplest form it is a metal disc with a pattern of wires, cutouts, and perforations that allows a user to calculate astronomical positions precisely. It is able to measure the [[horizontal coordinate system|altitude]] above the horizon of a celestial body, day or night; it can be used to identify stars or planets, to determine local [[latitude]] given [[local time]] (and vice versa), to survey, or to [[triangulation|triangulate]]. It was used in [[classical antiquity]], the [[Islamic Golden Age]], the European [[Middle Ages]] and the [[Age of Discovery]] for all these purposes.

The astrolabe, which is a precursor to the [[sextant]],<ref>
{{cite news
 |title=Historians' home yields rich lode
 |date=18 May 1964
 |newspaper=[[The New York Times]]
 |quote=New York Society searches its own building for items to mark anniversary; show opens Thursday; portrait of Stuyvesant and Champlain's astrolabe will be on display.
|url=https://www.nytimes.com/1964/05/18/archives/historians-home-yields-rich-lode-new-york-society-searches-its-own.html
 |access-date=4 February 2024
}}
</ref>
is effective for determining latitude on land or calm seas. Although it is less reliable on the heaving deck of a ship in rough seas, the [[mariner's astrolabe]] was developed to solve that problem.

== Applications ==
[[File:Lot-stoffler-johannes-1452-1531-elucidatio-fabricae-usuque-astrolabii-6069643.jpg|thumb|upright=1.4|16th&nbsp;century woodcut of measurement of a building's height with an astrolabe]]

The 10th&nbsp;century [[astronomer]] [[ʿAbd al-Raḥmān al-Ṣūfī]] wrote a massive text of 386&nbsp;chapters on the astrolabe, which reportedly described more than 1,000&nbsp;applications for the astrolabe's various functions.<ref>
{{cite encyclopedia
 |last=Bean |first=Adam L.
 |year=2009
 |title=astrolabes
 |editor-last=Birx |editor-first=H. James |editor-link=H. James Birx
 |encyclopedia=Encyclopedia of Time: Science, philosophy, theology, & culture
 |volume=1  |pages=59–60
 |publisher=SAGE
 |isbn=978-1-4129-4164-8
 |url=https://books.google.com/books?id=b3ddWSxmi9cC&pg=PA59
 |via=Google
}}
</ref>
These ranged from the astrological, the astronomical and the religious, to navigation, seasonal and daily time-keeping, and tide tables. At the time of their use, astrology was widely considered as much of a serious science as astronomy, and study of the two went hand-in-hand. The astronomical interest varied between folk astronomy (of the pre-Islamic tradition in Arabia) which was concerned with celestial and seasonal observations, and mathematical astronomy, which would inform intellectual practices and precise calculations based on astronomical observations. In regard to the astrolabe's religious function, the demands of Islamic prayer times were to be astronomically determined to ensure precise daily timings, and the [[qibla]], the direction of [[Mecca]] towards which Muslims must pray, could also be determined by this device. In addition to this, the [[lunar calendar]] that was informed by the calculations of the astrolabe was of great significance to the religion of Islam, given that it determines the dates of important religious observances such as [[Ramadan]].{{citation needed|date=March 2024}}

==Etymology==
The ''[[Oxford English Dictionary]]'' gives the translation "star-taker" for the English word ''astrolabe'' and traces it through medieval Latin to the [[Greek language|Greek]] word {{math|ἀστρολάβος}} : {{transliteration|grc|astrolábos}},<ref name=oed>
{{cite dictionary
 |title=astrolabe
 |dictionary=[[Oxford English Dictionary]] |edition=2nd
 |year=1989
 |url=http://dictionary.oed.com/cgi/entry/50013806
}}
</ref><ref>
{{cite dictionary
 |title=astrolabe
 |dictionary=[[Oxford Dictionaries (website)]]
 |url=http://oxforddictionaries.com/definition/english/astrolabe?q=astrolabe
 |url-status=dead |via=oxforddictionaries.com
 |archive-url=https://web.archive.org/web/20131022193917/http://www.oxforddictionaries.com/definition/english/astrolabe?q=astrolabe
 |archive-date=22 October 2013
}}
</ref>
from {{math|ἄστρον}}: {{transliteration|grc|astron}} "star", and {{math|λαμβάνειν}}: {{transliteration|grc|lambanein}} "to take".<ref>
{{cite dictionary
 |title=astrolabe
 |dictionary=Online Etymology Dictionary
 |url=http://www.etymonline.com/index.php?term=astrolabe
 |via=Etymonline.com |access-date=2013-11-07 |df=dmy-all
}}</ref>

In the medieval Islamic world the [[Arabic]] word {{transliteration|ar|al-asturlāb}} (i.e., astrolabe) was given various etymologies. In Arabic texts, the word is translated as {{transliteration|ar|ākhidhu al-nujūm}} ({{langx|ar|آخِذُ ٱلنُّجُومْ}}, {{lit|star-taker}}) – a direct translation of the Greek word.{{sfn|King|1981|p=44}}

[[Al-Biruni]] quotes and criticises medieval scientist [[Hamza al-Isfahani]], who stated:{{sfn|King| 1981|p= 44}}
: "''asturlab'' is an Arabisation of this Persian phrase" ({{transliteration|fa|sitara yab}}, meaning "taker of the stars").{{sfn|King|1981|p=51}}

In [[medieval Islam]]ic sources, there is also a [[folk etymology]] of the word as "lines of lab", where "Lab" refers to a certain son of [[Idris (prophet)|Idris]] ([[Enoch]]). This etymology is mentioned by a 10th&nbsp;century scientist named [[Ali Ibn Ibrahim Qomi|al-Qummi]] but rejected by [[al-Khwarizmi]].{{sfn|King|1981|p=45}}

==History==
===Ancient era===
An astrolabe is essentially a plane (two-dimensional) version of an [[armillary sphere]], which had already been invented in the [[Hellenistic period]] and probably been used by [[Hipparchus]] to produce his star catalogue. [[Theon of Alexandria]] ({{circa|335–405}}) wrote a detailed treatise on the astrolabe.{{sfn|Lewis|2001}} The invention of the plane astrolabe is sometimes wrongly attributed to Theon's daughter [[Hypatia]] (born {{circa|350–370}}; died {{nobr|415 {{sc|ce}}),}}<ref>
{{cite episode
 |first=Michael |last=Deakin
 |date=3 August 1997
 |title=Hypatia of Alexandria
 |series=Ockham's razor
 |publisher=[[Australian Broadcasting Corporation|ABC]] [[ABC Radio (Australia)|Radio]] 
 |type=radio program
}} Accessed 10&nbsp;July 2014.
</ref><ref name=Theodore>
{{cite book
 |last=Theodore |first=Jonathan
 |year=2016
 |title=The Modern Cultural Myth of the Decline and Fall of the Roman Empire
 |location=Manchester, UK
 |publisher=Palgrave, Macmillan
 |page=183
 |isbn=978-1-137-56997-4
 |url=https://books.google.com/books?id=3QPWDAAAQBAJ&pg=PA183  |via=Google
}}
</ref><ref name=Deakin2007>
{{cite book
 |last=Deakin |first=Michael A.B.
 |year=2007
 |title=Hypatia of Alexandria: Mathematician and martyr
 |location=Amherst, NY
 |publisher=Prometheus Books
 |pages=102–104
 |isbn=978-1-59102-520-7
 |url=https://books.google.com/books?id=P6X1DJ7UIb4C&pg=PA135  |via=Google
}}
</ref><ref name=Bradley>
{{cite book
 |last=Bradley |first=Michael John
 |year=2006
 |title=The Birth of Mathematics: Ancient times to 1300
 |location=New York City, NY
 |publisher=Infobase Publishing
 |page=63
 |isbn=9780816054237
 |url=https://books.google.com/books?id=EIdtVPeD7GcC&pg=PA63  |via=Google
}}
</ref>
but it is known to have been used much earlier.<ref name=Theodore/><ref name=Deakin2007/><ref name=Bradley/>
The misattribution comes from a misinterpretation of a statement in a letter written by Hypatia's pupil [[Synesius]] ({{circa|373–414}}),<ref name=Theodore/><ref name=Deakin2007/><ref name=Bradley/>
which mentions that Hypatia had taught him how to construct a plane astrolabe, but does not say that she invented it.<ref name=Theodore/><ref name=Deakin2007/><ref name=Bradley/>
Lewis argues that [[Ptolemy]] used an astrolabe to make the astronomical observations recorded in the ''[[Tetrabiblos]]''.{{sfn|Lewis|2001}} However, [[Emilie Savage-Smith]] notes
:"there is no convincing evidence that Ptolemy or any of his predecessors knew about the planispheric astrolabe".<ref name=SavageSmith-1992>
{{cite book
 |last=Savage-Smith |first=E. |author-link=Emilie Savage-Smith
 |url=https://press.uchicago.edu/books/HOC/HOC_V2_B1/Volume2_Book1.html
 |title=The History of Cartography
 |volume=2, Book&nbsp;1: Cartography in the traditional Islamic and South Asian societies
 |date=1992
 |place=Chicago, IL
 |publisher=University of Chicago Press
 |isbn=0226316351
 |editor1-last=Harley |editor1-first=J.B.
 |series=The History of Cartography
 |chapter=Celestial mapping
 |editor-last2=Woodward |editor-first2=David
 |chapter-url=https://press.uchicago.edu/books/HOC/HOC_V2_B1/HOC_VOLUME2_Book1_chapter2.pdf
}}
</ref>

In chapter&nbsp;5.1 of the ''[[Almagest]]'', Ptolemy describes the construction of an [[armillary sphere]], and it is usually assumed that this was the instrument he used.

Astrolabes continued to be used in the [[Byzantine Empire]]. Christian philosopher [[John Philoponus]] wrote a treatise ({{circa|550}}) on the astrolabe in Greek, which is the earliest extant treatise on the instrument.<ref>
Modern editions of [[John Philoponus]]' treatise on the astrolabe are
:
{{cite book
 |first=John |last=Philoponus  |author-link=John Philoponus
 |year=1839  |orig-year={{circa|550}}
 |title=De usu astrolabii eiusque constructione libellus |lang=la
 |trans-title=On the Use and Construction of the Astrolabe
 |editor-first=Heinrich |editor-last=Hase
 |place=Bonn, DE
 |publisher=E. Weber
 |OCLC=165707441
}}<br/>
or<br/>
{{cite book
 |first=John |last=Philoponus  |author-link=John Philoponus
 |year=1839  |orig-year={{circa|550}}
 |title=De usu astrolabii eiusque constructione libellus |lang=la
 |trans-title=On the Use and Construction of the Astrolabe
 |edition=reprint
 |series=Rheinisches Museum für Philologie
 |volume=6 |pages=127–171
}}
:
repr. and translated into French<br/>
{{cite book
 |first=Alain Philippe |last=Segonds
 |title=''Jean Philopon,'' traité de l'astrolabe |lang=fr, la
 |place=Paris, FR
 |publisher=Librairie Alain Brieux
 |year=1981  |orig-year={{circa|550}}
 |OCLC=10467740
 |others=[[John Philoponus|Philoponus, John]] (''Jean Philopon'', original author)
}} 
:
translated into English and included as part of<br/>
{{cite book
 |first=John |last=Philoponus  |author-link=John Philoponus
 |year=1932  |orig-year={{circa|550}}
 |section=On the Use and Construction of the Astrolabe [''De usu astrolabii eiusque constructione libellus'']
 |lang=en
 |translator-first=H.W. |translator-last=Green
 |editor-first=R.T.     |editor-last=Gunther
 |title=The Astrolabes of the World
 |volume=1 (of 2)
 |publisher=Oxford
 |OL=18840299M
}}<br/>
: which was reprinted in 1976:
{{cite book
 |first=John |last=Philoponus  |author-link=John Philoponus
 |year=1976  |orig-year={{circa|550}}
 |title=On the Use and Construction of the Astrolabe |lang=en
 |trans-title=De usu astrolabii eiusque constructione libellus
 |translator-first=H.W. |translator-last=Green
 |edition=reprint
 |place=London, UK
 |publisher=Holland Press
 |OL=14132393M
 |pages=61–81
}}
</ref>
[[Mesopotamian]] bishop [[Severus Sebokht]] also wrote a treatise on the astrolabe in the [[Syriac language]] during the mid-7th century.{{efn|
"The most distinguished Syriac scholar of this later period was [[Severus Sebokht]] (d.&nbsp;666–667), Bishop of Kennesrin. ... In addition to these works ... he also wrote on astronomical subjects (Brit. Mus. Add.&nbsp;14538), and composed a treatise on the astronomical instrument known as the astrolabe, which has been edited and published by F.&nbsp;Nau (Paris, 1899)."<ref>
{{cite book
 |last = O'Leary |first = de Lacy |author-link=de Lacy O'Leary
 |title = How Greek Science Passed to the Arabs
 |date = 1948
 |publisher = Routledge and Kegan Paul
 |url = http://www.aina.org/books/hgsptta.htm
}}
</ref> {{right|{{nobr| — {{harvp|O'Leary|1948}}}} }}<br/><br/>
:
Severus' treatise was translated by {{harvp|Smith Margoliouth|1932}}.<ref>
{{cite book
 |first=Jessie Payne |last=Smith Margoliouth
 |year=1932
 |editor-first=R.T. |editor-last=Gunther
 |title=Astrolabes of the World
 |publisher=Oxford
 |pages=82–103
 |others=[[Severus Sebokht|Sebokht, Severus]] (original author)
}}
</ref>
}}
Sebokht refers to the astrolabe as being made of brass in the introduction of his treatise, indicating that metal astrolabes were known in the Christian East well before they were developed in the Islamic world or in the Latin West.<ref>
{{cite web
 |first=Severus |last=Sebokht
 |title=Description of the astrolabe
 |website=Tertullian.org
 |url=http://www.tertullian.org/fathers/severus_sebokht_astrolabe_01_trans.htm
}}
</ref>

===Medieval era===
Astrolabes were further developed in the [[Islamic Golden Age|medieval Islamic world]], where [[Astronomy in medieval Islam|Muslim astronomers]] introduced angular scales to the design,<ref>See p.&nbsp;289 of {{Citation
| doi = 10.1088/1475-4878/24/5/302| issn = 1475-4878| volume = 24| issue = 5| pages = 289–303| last = Martin| first = L. C.| title = Surveying and navigational instruments from the historical standpoint| journal = Transactions of the Optical Society| date = 1923| postscript = .|bibcode = 1923TrOS...24..289M }}</ref> adding circles indicating [[azimuth]]s on the [[horizon]].<ref>{{citation|title=The Mathematics of Egypt, Mesopotamia, China, India, and Islam: a Sourcebook|editor-first=Victor J.|editor-last=Katz|first=J. Lennart|last=Berggren|chapter=Mathematics in Medieval Islam|chapter-url=https://books.google.com/books?id=3ullzl036UEC&pg=PA519|publisher=[[Princeton University Press]]|date=2007|isbn=978-0-691-11485-9|page=519}}</ref> It was widely used throughout the Muslim world, chiefly as an [[Geography in medieval Islam|aid to navigation]] and as a way of finding the [[Qibla]], the direction of [[Mecca]]. Eighth-century [[Mathematics in medieval Islam|mathematician]] [[Muhammad al-Fazari]] is the first person credited with building the astrolabe in the Islamic world.<ref>[[Richard Nelson Frye]]: ''Golden Age of Persia''. p. 163</ref>

The mathematical background was established by Muslim astronomer [[Muhammad ibn Jābir al-Harrānī al-Battānī|Albatenius]] in his treatise ''Kitab az-Zij'' {{nobr|({{circa| 920 {{sc|ce}} }}),}} which was translated into Latin by [[Plato Tiburtinus]] (''De Motu Stellarum''). The earliest surviving astrolabe is dated [[Islamic calendar|AH]] 315 {{nobr|(927–928 {{sc|ce}}).}} 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&nbsp;different uses of an astrolabe, in areas as diverse as [[astronomy]], [[Islamic astrology|astrology]], [[mariner's astrolabe|navigation]], [[surveying]], timekeeping, prayer, [[Salat]], [[Qibla]], etc.<ref>
{{cite web
 |last=Nizamoglu |first=Cem
 |date=2005-08-10
 |title=Using an astrolabe
 |website=Muslim Heritage (muslimheritage.com)
 |url=https://muslimheritage.com/using-an-astrolabe/
 |access-date=2023-10-16 |df=dmy-all
}}
</ref><ref>
{{cite book
 |last1=Lachièz-Rey |first1=Marc
 |last2=Luminet     |first2=Jean-Pierre
 |year=2001
 |title=Celestial Treasury: From the music of spheres to the conquest of space
 |translator-first=Joe |translator-last=Laredo
 |place=Cambridge, UK
 |publisher=Cambridge University Press
 |isbn=978-0-521-80040-2
 |page=74
 |lang=en
}}
</ref>

[[File:Astrolabium.jpg|thumb|An Arab astrolabe from 1208]]
The [[spherical astrolabe]] was a variation of both the astrolabe and the [[armillary sphere]], invented during the [[Middle Ages]] by astronomers and [[Inventions in the Muslim world|inventors]] in the Islamic world.{{efn|
"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."<ref>
{{cite journal
 |first=Emilie |last=Savage-Smith |author-link=Emilie Savage-Smith
 |year=1993
 |title=Book Reviews
 |journal=[[Journal of Islamic Studies]]
 |volume=4 |issue=2 |pages=296–299
 |doi=10.1093/jis/4.2.296}}
</ref>
}}
The earliest description of the spherical astrolabe dates to [[Al-Nayrizi]] ([[floruit|fl.]] 892–902). In the 12th&nbsp;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".<ref name=MacTutor>{{MacTutor|id=Al-Tusi_Sharaf|title=Sharaf al-Din al-Muzaffar al-Tusi}}</ref> The geared mechanical astrolabe was invented by Abi Bakr of [[Isfahan]] in 1235.<ref name=Bedini>
{{cite journal
 |first1=Silvio A.  |last1=Bedini    |author-link1=Silvio Bedini
 |first2=Francis R. |last2=Maddison  |author-link2=Francis Maddison
 |year=1966 |title=Mechanical universe: The astrarium of Giovanni de'&nbsp;Dondi
 |journal=[[Transactions of the American Philosophical Society]]
 |volume=56 |issue=5 |pages=1–69
 |jstor=1006002 |doi=10.2307/1006002
}}
</ref>

The first known metal astrolabe in Western Europe is the Destombes astrolabe made from brass in the eleventh century in Portugal.<ref>{{cite web |title='Carolingian' astrolabe |website=Qantara (qantara-med.org) |url=http://www.qantara-med.org/qantara4/public/show_document.php?do_id=1379&lang=en |access-date=2013-11-07}}</ref><ref name=Brown-2010/>{{rp|style=ama|p= 140}} Metal astrolabes avoided the warping that large wooden ones were prone to, allowing the construction of larger and therefore more accurate instruments. Metal astrolabes were heavier than wooden instruments of the same size, making it difficult to use them in navigation.<ref>{{cite book |first=David |last=Boyle |year=2011 |title=Toward the Setting Sun: Columbus, Cabot, Vespucci, and the race for America |publisher=Bloomsbury Publishing |place=USA |isbn=9780802779786 |page=253|url=https://books.google.com/books?id=x92SNeDpKqsC&pg=PA253 }}</ref>

[[File:Spherical astrolabe.jpg|thumb|Spherical astrolabe]]
[[File:Euclid and Herman - Ashmole MS 304, fol 2.jpg|thumb|A depiction of [[Hermann of Reichenau]] with an astrolabe in a 13th&nbsp;century manuscript by Matthew Paris]]
[[Herman Contractus]] of [[Reichenau Abbey]], examined the use of the astrolabe in ''Mensura Astrolai'' during the 11th&nbsp;century.<ref name=Northrup-2015-EWT>
{{cite book
 |editor=Northrup |editor-first=Cynthia Clark
 |year=2015
 |title=Encyclopedia of World Trade: From ancient times to the present
 |place=Armonk, NY
 |publisher=Routledge
 |isbn=978-0765680587
 |edition=Enhanced Credo
 |oclc=889717964 |lang=en-us
 |pages=[https://archive.org/details/encyclopediaofwo0000unse_d8h7/page/72 72], [https://archive.org/details/encyclopediaofwo0000unse_d8h7/page/460 460]
 |url=https://archive.org/details/encyclopediaofwo0000unse_d8h7
}}
</ref>{{rp|style=ama|p= [https://archive.org/details/encyclopediaofwo0000unse_d8h7/page/72 72] }}
[[Peter of Maricourt]] wrote a treatise on the construction and use of a universal astrolabe in the last half of the 13th&nbsp;century entitled ''Nova compositio astrolabii particularis''. Universal astrolabes can be found at the [[History of Science Museum, Oxford]].<ref>{{cite web |title=Introduction |year=2006 |department=The astrolabe: An online resource |series=[[History of Science Museum, Oxford|History of Science Museum]] |place=Oxford, UK |publisher=[[Oxford University]] |url=https://www.mhs.ox.ac.uk/astrolabe/ |access-date=2020-05-15 }}</ref> David A. King, historian of Islamic instrumentation, describes the universal astrolobe designed by Ibn al-Sarraj of [[Aleppo]] (a.k.a. Ahmad bin Abi Bakr; fl. 1328) as "the most sophisticated astronomical instrument from the entire Medieval and Renaissance periods".<ref>{{cite book |last1=Harley |first1=J.B. |last2=Woodward |first2=David |year=1992 |title=The History of Cartography |publisher=University of Chicago Press |isbn=0-226-31635-1 |location=Chicago, IL |page=31 |lang=en-us }}</ref>

English author [[Geoffrey Chaucer]] ({{circa|1343–1400}}) compiled ''[[A Treatise on the Astrolabe]]'' for his son, mainly based on a work by [[Mashallah ibn Athari|Messahalla]] or [[Ibn al-Saffar]].<ref>{{cite journal |last = Kunitzsch |first = Paul |year = 1981 |title = On the authenticity of the treatise on the composition and use of the astrolabe ascribed to Messahalla |journal = Archives Internationales d'Histoire des Sciences, Oxford |volume = 31 |issue = 106 |pages = 42–62 }}</ref><ref name=Selin-2008>{{cite book |last = Selin |first = Helaine |date = 2008-03-12 |title = Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures |publisher = Springer Science & Business Media | isbn = 978-1-4020-4559-2 |url = https://archive.org/details/encyclopaediahis00seli |url-access = limited |page=[https://archive.org/details/encyclopaediahis00seli/page/n1347 1335] }}</ref>{{efn|
"Paul Kunitzsch has recently established that the Latin treatise on the astrolabe long ascribed to Ma'sh'allah and translated by John of Seville is in fact by Ibn al-Saffar, a disciple of Maslama al-Majriti."<ref name=Selin-2008/>}}
The same source was translated by 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.

[[File:Front_of_a_Sanskrit_Astrolabe.jpg|left|thumb|Front of an [[Indian astrolabe]] now kept at the [[National Museum of Scotland|Royal Museum of Scotland at Edinburgh.]]]]
In 1370, the first Indian treatise on the astrolabe was written by the [[Jainism|Jain]] astronomer [[Mahendra Suri]], titled ''Yantrarāja''.<ref>{{cite book |editor1-first=Thomas |editor1-last=Glick |editor2-first=Steven J. |editor2-last=Livesey |editor3-first=Faith |editor3-last=Wallis |year = 2005 |title = Medieval Science, Technology, and Medicine: An encyclopedia |publisher = Routledge |isbn = 0-415-96930-1 | page = 464 |url=https://books.google.com/books?id=SaJlbWK_-FcC&pg=PA464 }}</ref>

A simplified astrolabe, known as a ''balesilha'', was used by sailors to get an accurate reading of latitude while at sea. The use of the ''balesilha'' was promoted by [[Prince Henry the Navigator|Prince Henry]] (1394–1460) while navigating for Portugal.<ref name=Northrup-2015-EWT/>{{rp|style=ama|p= [https://archive.org/details/encyclopediaofwo0000unse_d8h7/page/460 460] }}

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.<ref name=Brown-2010>{{cite book |first=Nancy Marie |last=Brown |year=2010 |title=The Abacus and the Cross |pages=140, 143 |publisher=Basic Books |ISBN=978-0-465-00950-3 }}</ref>{{rp|style=ama|p= 143}} In the 15th&nbsp;century, French instrument maker Jean Fusoris ({{circa|1365–1436}}) also started remaking and selling astrolabes in his shop in [[Paris]], along with portable sundials and other popular scientific devices of the day.[[File:Detail of Astronomical Instrument Ieremias Palladas.png|thumb|upright=1|left|[[Saint Catherine of Alexandria (Palladas, Sinai)#Scientific Element|Astronomical Instrument]] Detail by [[Ieremias Palladas]] 1612]] Thirteen of his astrolabes survive to this day.<ref>{{cite book |title=The Biographical Encyclopedia of Astronomers |last=Hockey |first=Thomas |date=2009 |publisher=[[Springer Publishing]] |isbn=978-0-387-31022-0 |access-date=August 22, 2012 |url=http://www.springerreference.com/docs/html/chapterdbid/58493.html}}</ref> One more special example of craftsmanship in early 15th-century Europe is the astrolabe designed by Antonius de Pacento and made by Dominicus de Lanzano, dated 1420.<ref>{{cite book |first=Ralf |last=Kern |year=2010 |title=Wissenschaftliche Instrumente in ihrer Zeit |lang=de |trans-title=Scientific Instruments in their Era |volume=1:&nbsp;Vom Astrolab zum mathematischen Besteck [From the astroabe to mathematical instruments] |place=Köln, DE |publisher=König |ISBN=978-3-86560-865-9 |page=204 }}</ref>

In the 16th&nbsp;century, [[Johannes Stöffler]] published ''Elucidatio fabricae ususque astrolabii'', a manual of the construction and use of the astrolabe. Four identical 16th&nbsp;century astrolabes made by [[Georg Hartmann]] provide some of the earliest evidence for [[batch production]] by [[division of labor]].

Greek painter [[Ieremias Palladas]] incorporated a sophisticated astrolabe in his 1612 painting depicting [[Catherine of Alexandria]]. The painting, entitled [[Saint Catherine of Alexandria (Palladas, Sinai)#Scientific Element|''Catherine of Alexandria'']]; in addition to the saint, showed a device labelled the 'system of the universe' ({{math|Σύστημα τοῦ Παντός}}). The device featured the [[classical planets]] with their Greek names: [[Helios]] (Sun), [[Selene]] (Moon), [[Hermes]] (Mercury), [[Aphrodite]] (Venus), [[Ares]] (Mars), [[Zeus]] (Jupiter), and [[Cronus|Cronos]] (Saturn). The depicted device also had celestial spheres, following the [[Ptolemaic model]], and Earth was shown as a blue sphere with circles of geographic coordinates. A complicated line representing the axis of the Earth covered the entire instrument.<ref name=astro>
{{cite journal
 |last=Vafea |first=Flora
 |year=2017
 |title=The astronomical instruments in Saint Catherine's iconography at the Holy Monastery of Sinai
 |journal=Almagest
 |volume=8 |issue=2 |pages=85-109, {{nobr|esp. p. 87}}
 |issn=1792-2593 |doi=10.1484/J.ALMAGEST.5.114932
 <!-- |place=Paris, FR |publisher=[[ University of Paris]] -->
 |url=https://www.brepolsonline.net/doi/abs/10.1484/J.ALMAGEST.5.114932?mobileUi=0
 |via=brepolsonline.net
 |url-access=subscription |access-date=2024-11-20
}}
</ref>

{{Gallery
|title=Medieval astrolabes
|align=center
|File:Tusi manus.jpg|A treatise explaining the importance of the astrolabe by [[Nasir al-Din al-Tusi]], Persian scientist
|File:Jean Fusoris planispheric astrolabe in Putnam Gallery, 2009-11-24.jpg|Astrolabe of [[Jean Fusoris]], made in [[Paris]], 1400
|File:Astrolabe-Persian-18C.jpg|An 18th-century [[Persia]]n astrolabe
|File:Astrolabe, 18th century, disassembled.jpg|Disassembled 18th-century astrolabe
|File:Astrolabium im Mathematisch-Physikalischen Salon (Zwinger, Dresden).jpg|Exploded view of an astrolabe
|File:Astrolabe - Stereographic projection on tympan.gif|Animation showing how [[celestial coordinate system|celestial]] and [[geographic coordinate system|geographic coordinates]] are mapped on an astrolabe's tympan through a [[stereographic projection]]. Hypothetical tympan ([[40th parallel north|40° north latitude]]) of a 16th-century European [[planisphere|planispheric]] astrolabe.
|File:Libro Primero del Astrolabio Redondo (Libros del saber de astronomía).jpg|Astrolabe manual from the [[Alfonso X of Castile]] work [[Libros del saber de astronomía]], 1276.
|File:Astrolabium Masha'allah Public Library Brugge Ms. 522.tif|A page from the 1575 book "Astrolabium" depicting an astrolabe. Masha'Allah {{Interlanguage link multi|Public Library Bruges|nl|3=Openbare Bibliotheek Brugge}} Ms. 522
}}

===Astrolabes and clocks===
[[File:Het gebruik van het astrolabium door Amerigo Vespucci, Jan Collaert II, Museum Plantin-Moretus, PK.OPB.0186.018.jpg|thumb|upright=1.4|[[Amerigo Vespucci]] observing the [[Crux|Southern Cross]] by looking over the top of an [[armillary sphere]] bizarrely held from the top as if it were an astrolabe; however, an astrolabe cannot be used by looking over its top. The page inexplicably contains the word ''astrolabium''. By [[Jan Collaert II]]. [[Museum Plantin-Moretus]], [[Antwerp]], Belgium.]]

Mechanical [[astronomical clock]]s were initially influenced by the astrolabe; they could be seen in many ways as clockwork astrolabes designed to produce a continual display of the current position of the sun, stars, and planets. For example, [[Richard of Wallingford]]'s clock ({{circa|1330}}) consisted essentially of a star map rotating behind a fixed rete, similar to that of an astrolabe.{{sfn|North| 2005}}

Many astronomical clocks use an astrolabe-style display, such as the famous [[Prague Orloj|clock at Prague]], adopting a stereographic projection (see below) of the ecliptic plane. In recent times, astrolabe watches have become popular. For example, Swiss watchmaker [[Ludwig Oechslin]] designed and built an astrolabe wristwatch in conjunction with [[Ulysse Nardin]] in 1985.<ref>{{cite web |url=http://www.ulysse-nardin.ch/en/swiss_watch_manufacturer/Collection/Archive/Astrolabium_G._Galilei.html |url-status=dead |archive-url=https://web.archive.org/web/20110102024043/http://www.ulysse-nardin.ch/en/swiss_watch_manufacturer/Collection/Archive/Astrolabium_G._Galilei.html |archive-date=2 January 2011 |title=Astrolabium G. Galilei |website=Ulysse Nardin}}</ref> Dutch watchmaker Christaan van der Klauuw also manufactures astrolabe watches today.<ref>{{cite web |url=http://www.klaauw.com/ |title=Christaan van der Klauuw}}</ref>

==Construction==
An astrolabe consists of a disk with a wide, raised rim, called the ''mater'' (mother), which is deep enough to hold one or more flat plates called ''tympans'', or ''[[Clime|climates]]''. A [[tympan]] is made for a specific [[latitude]] and is engraved with a [[stereographic projection]] of [[circle]]s denoting [[azimuth]] and [[Horizontal coordinate system|altitude]] and representing the portion of the [[celestial sphere]] above the local horizon. The rim of the mater is typically graduated into [[hour|hours of time]], [[degree (angle)|degrees of arc]], or both.<ref name="Stephenson 2000 108–109">{{cite book |last1=Stephenson|first1=Bruce |first2=Marvin|last2=Bolt |first3=Anna Felicity|last3=Friedman |title=The Universe Unveiled: Instruments and images through history|year=2000|publisher=Cambridge University Press|location=Cambridge, UK|isbn=0-521-79143-X|pages=108–109}}</ref>

Above the mater and tympan, the ''rete'', a framework bearing a projection of the [[ecliptic]] plane and several [[Pointer (rod)|pointers]] indicating the positions of the brightest [[star]]s, 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.<ref name="Stephenson 2000 108–109"/> The names of the indicated stars were often engraved on the pointers in Arabic or Latin.<ref>{{cite web|url=http://www.ianridpath.com/startales/astrolabe.html|title=Star Names on Astrolabes|publisher=Ian Ridpath|access-date=2016-11-12}}</ref> Some astrolabes have a narrow ''[[ruler|rule]]'' or ''label'' which rotates over the rete, and may be marked with a scale of [[declination]]s.

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 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. The alidade had vertical and horizontal cross-hairs which plots locations on an azimuthal ring called an almucantar (altitude-distance circle).

An arm called a radius connects from the center of the astrolabe to the optical axis which is parallel with another arm also called a radius. The other radius contains graduations of altitude and distance measurements.

A shadow square also appears on the back of some astrolabes, developed by Muslim astrologists in the 9th Century, whereas devices of the Ancient Greek tradition featured only altitude scales on the back of the devices.<ref>{{Cite book|last=King|first=David A.|title=Some Medieval Astronomical Instruments and Their Secrets, in Mazzolini, R. G. (ed.), Non-Verbal Communication in Science prior to 1900|publisher=[[Florence]]|pages=30}}</ref> This was used to convert shadow lengths and the altitude of the sun, the uses of which were various from surveying to measuring inaccessible heights.<ref>{{Cite book |last=King |first=David A. |title=The Astrolabe: What it is & what it is not |publisher=[[Frankfurt]] |year=2018 |location=Frankfurt, Germany}}</ref>

Devices were usually signed by their maker with an inscription appearing on the back of the astrolabe, and if there was a patron of the object, their name would appear inscribed on the front, or in some cases, the name of the reigning sultan or the teacher of the astrolabist has also been found to appear inscribed in this place.<ref name=":0">{{Cite book |last=Mayer |first=L. A. |title=Islamic astrolabists and their works |publisher=A. Kunding |year=1956 |bibcode=1956iatw.book.....M}}</ref> The date of the astrolabe's construction was often also signed, which has allowed historians to determine that these devices are the second oldest scientific instrument in the world. The inscriptions on astrolabes also allowed historians to conclude that astronomers tended to make their own astrolabes, but that many were also made to order and kept in stock to sell, suggesting there was some contemporary market for the devices.<ref name=":0" />

{{Gallery
|title=Construction of astrolabes
|align=center
|File:Yale's Hartmann astrolabe.jpg|The [[Georg Hartmann|Hartmann]] astrolabe in [[Yale University|Yale]] collection. This instrument shows its rete and rule.
|File:Globe Celeste Louvre Asturlabi DSC 0713.JPG|Celestial Globe, Isfahan (?), Iran 1144. Shown at the [[Louvre Museum]], this globe is the third oldest surviving in the world.
|File:Planispheric astrolabe.png|Computer-generated planispheric astrolabe
}}

== Mathematical basis ==
The construction and design of astrolabes are based on the application of the [[stereographic projection]] of the [[celestial sphere]]. The point from which the projection is usually made is the [[South Pole]]. The plane onto which the projection is made is that of the [[Equator]].<ref>{{Cite journal |last1=Gentili |first1=Graziano |last2=Simonutti |first2=Luisa |last3=Struppa |first3=Daniele C. |title=The Mathematics of the Astrolabe and its History |url=https://scholarship.claremont.edu/cgi/viewcontent.cgi?article=1560&context=jhm |journal=Journal of Humanistic Mathematics |date=2020 |volume=10 |pages=101–144|doi=10.5642/jhummath.202001.07 |s2cid=211008813 |doi-access=free |hdl=2158/1182616 |hdl-access=free }}</ref>

=== Designing a tympanum through stereographic projection ===
[[File:Parts of a tympan of an astrolabe.png|thumb|upright=1.4|Parts of an Astrolabe tympanum]]

The tympanum captures the celestial coordinate axes upon which the ''rete'' will rotate. It is the component that will enable the precise determination of a star's position at a specific time of [[Earth's rotation|day]] and [[Earth's orbit|year]].

Therefore, it should project:

# The [[zenith]], which will vary depending on the [[latitude]] of the astrolabe user.
# The [[Horizon|horizon line]] and [[almucantar]] or circles parallel to the horizon, which will allow for the determination of a celestial body's [[Horizontal coordinate system|altitude]] (from the horizon to the zenith).
# The [[Meridian (astronomy)|celestial meridian]] (north-south meridian, passing through the zenith) and secondary meridians (circles intersecting the north-south meridian at the zenith), which will enable the measurement of [[azimuth]] for a celestial body.
# The three main [[Circle of latitude|circles of latitude]] ([[Tropic of Capricorn|Capricorn]], [[Equator]], and [[Tropic of Cancer|Cancer]]) to determine the exact moments of [[solstice]]s and [[equinox]]es throughout the year.

==== The tropics and the equator define the tympanum ====
[[File:Proyección estereográfica de trópicos y ecuador en un astrolabio.png|thumb|upright=2.8|Stereographic projection of Earth's tropics and equator from the South Pole.]]
On the right side of the image above:

# {{color box|#C4F5F5}} The blue sphere represents the [[celestial sphere]].
# {{color box|#0325F1}} The blue arrow indicates the direction of true north (the [[Polaris|North Star]]).
# {{color box|#0325F1}} The central blue point represents Earth (the observer's location).
# {{color box|#001919}} The geographic south of the celestial sphere acts as the [[Stereographic projection|projection pole]].
# {{color box|#B8B8B8}} The celestial equatorial plane serves as the [[projection plane]].
# Three parallel circles represent the projection on the celestial sphere of Earth's main [[Circle of latitude|circles of latitude]]: 
#* {{color box|#DA5E1B}} In orange, the celestial [[Tropic of Cancer]]. 
#* {{color box|#8533DB}} In purple, the celestial [[equator]].
#* {{color box|#006713}} In green, the celestial [[Tropic of Capricorn]].

When projecting onto the celestial equatorial plane, three concentric circles correspond to the celestial sphere's three [[Circle of latitude|circles of latitude]] (left side of the image). The largest of these, the projection on the celestial equatorial plane of the celestial [[Tropic of Capricorn]], defines the size of the astrolabe's tympanum. The center of the tympanum (and the center of the three circles) is actually the north-south axis around which Earth rotates, and therefore, the ''rete'' of the astrolabe will rotate around this point as the hours of the day pass (due to [[Earth's rotation|Earth's rotational motion]]).

The three concentric circles on the tympanum are useful for determining the exact moments of [[solstice]]s and [[equinox]]es throughout the year: if the sun's altitude at noon on the ''rete'' is known and coincides with the outer circle of the tympanum (Tropic of Capricorn), it signifies the [[winter solstice]] (the sun will be at the [[zenith]] for an observer at the Tropic of Capricorn, meaning summer in the southern hemisphere and winter in the northern hemisphere). If, on the other hand, its altitude coincides with the inner circle (Tropic of Cancer), it indicates the [[summer solstice]]. If its altitude is on the middle circle (equator), it corresponds to one of the two [[equinox]]es.

==== The horizon and the measurement of altitude ====
[[File:Proyección estereográfica del horizonte sobre el tímpano de un astrolabio.png|thumb|upright=2.8|Stereographic projection of an observer's horizon at a specific latitude]]
On the right side of the image above:

# {{color box|#0325F1}} The blue arrow indicates the direction of true north (the [[Polaris|North Star]]).
# {{color box|#0325F1}} The central blue point represents Earth (the observer's location).
# {{color box|#001919}} The black arrow represents the [[zenith]] direction for the observer (which would vary depending on the observer's [[latitude]]).
# {{color box|#001919}} The two black circles represent the [[horizon]] surrounding the observer, which is perpendicular to the zenith vector and defines the portion of the [[celestial sphere]] visible to the observer, and its projection on the celestial equatorial plane. 
# {{color box|#001919}} The geographic south of the celestial sphere acts as the [[Stereographic projection|projection pole]].
# {{color box|#B8B8B8}} The celestial equatorial plane serves as the [[projection plane]].

When projecting the [[horizon]] onto the celestial equatorial plane, it transforms into an ellipse upward-shifted relatively to the center of the tympanum (both the observer and the projection of the north-south axis). This implies that a portion of the celestial sphere will fall outside the outer circle of the tympanum (the projection of the celestial [[Tropic of Capricorn]]) and, therefore, won't be represented.

[[File:Proyección estereográfica del horizonte y almucantar sobre el tímpano de un astrolabio.png|thumb|Stereographic projection of the horizon and an almucantar.|upright=2.8]]

Additionally, when drawing circles parallel to the horizon up to the zenith ([[almucantar]]), and projecting them on the celestial equatorial plane, as in the image above, a grid of consecutive ellipses is constructed, allowing for the determination of a [[Horizontal coordinate system|star's altitude]] when its ''rete'' overlaps with the designed tympanum.

==== The meridians and the measurement of azimuth ====
[[File:Proyección estereográfica del horizonte y azimut sobre el tímpano de un astrolabio.png|thumb|upright=2.8|Stereographic projection of the north-south meridian and a meridian 40° E on the tympanum of an astrolabe]]

On the right side of the image above:

# {{color box|#0325F1}} The blue arrow indicates the direction of true north (the [[Polaris|North Star]]).
# {{color box|#0325F1}} The central blue point represents Earth (the observer's location).
# {{color box|#001919}} The black arrow represents the [[zenith]] direction for the observer (which would vary depending on the observer's [[latitude]]).
# {{color box|#001919}} The two black circles represent the [[horizon]] surrounding the observer, which is perpendicular to the zenith vector and defines the portion of the [[celestial sphere]] visible to the observer, and its projection on the celestial equatorial plane.
# {{color box|#D92929}} The five red dots represent the [[zenith]], the [[nadir (astronomy)|nadir]] (the point on the [[celestial sphere]] opposite the zenith with respect to the observer), their projections on the celestial equatorial plane, and the center (with no physical meaning attached) of the circle obtained by projecting the secondary meridian (see below) on the celestial equatorial plane.
# {{color box|#DA5E1B}} The orange circle represents the [[Meridian (astronomy)|celestial meridian]] (or meridian that goes, for the observer, from the north of the horizon to the south of the horizon passing through the zenith).
# {{color box|#D92929}} The two red circles represent a secondary meridian with an [[azimuth]] of 40° East relative to the observer's horizon (which, like all secondary meridians, intersects the principal meridian at the zenith and nadir), and its projection on the celestial equatorial plane.
# {{color box|#001919}} The geographic south of the celestial sphere acts as the [[Stereographic projection|projection pole]].
# {{color box|#B8B8B8}} The celestial equatorial plane serves as the [[projection plane]].

When projecting the [[Meridian (astronomy)|celestial meridian]], it results in a straight line that overlaps with the vertical axis of the tympanum, where the [[zenith]] and [[nadir (astronomy)|nadir]] are located. However, when projecting the 40° E meridian, another circle is obtained that passes through both the zenith and nadir projections, so its center is located on the perpendicular [[bisection]] of the segment connecting both points. In deed, the projection of the celestial meridian can be considered as a circle with an infinite radius (a straight line) whose center is on this bisection and at an infinite distance from these two points.

If successive meridians that divide the celestial sphere into equal sectors (like "orange slices" radiating from the zenith) are projected, a family of curves passing through the zenith projection on the tympanum is obtained. These curves, once overlaid with the ''rete'' containing the major stars, allow for determining the [[azimuth]] of a star located on the ''rete'' and rotated for a specific time of day.

==See also==
{{div col begin|colwidth=15em}}
* [[astronomy in the medieval Islamic world]]
* [[equatorium]]
* [[Hamburg Planetarium]]
* [[list of astronomical instruments]]
* [[Philippe Danfrie]], designer and maker of [[mathematical instrument]]s, globes and astrolabes
* [[planisphere]]
* [[planetarium]]
* [[Volvelle]]
* [[Yantraraja]]
* [[Zeiss-Planetarium Jena]]
{{div col end}}

==Footnotes==
{{notelist}}

==References==
{{reflist|25em}}

==Bibliography==
* {{Citation |last=Evans |first=James |date=1998 |title=The History and Practice of Ancient Astronomy |publisher=Oxford University Press |isbn=0-19-509539-1 |ref=none}}
* {{Citation |translator-last1=Gunella |translator-first1=Alessandro |translator-last2=Lamprey |translator-first2=John |trans-title=Elucidatio Fabricae Ususque Astrolabii |date=2007 |publisher=John Lamprey |last=Stöffler |first=Johannes |author-link=Johannes Stöffler |title=Stoeffler's Elucidatio – The Construction and Use of the Astrolabe |orig-date=First published 1513 |isbn=978-1-4243-3502-2 |ref=none}}
* {{Citation |last=King |first=D. A. |date=1981 |title=The Origin of the Astrolabe According to the Medieval Islamic Sources |journal=Journal for the History of Arabic Science |volume=5 |pages=43–83}}
* {{Citation |last=King |first=Henry |date=1978 |title=Geared to the Stars: the Evolution of Planetariums, Orreries, and Astronomical Clocks |publisher=University of Toronto Press |isbn=978-0-8020-2312-4 |ref=none}}
* {{Citation |last1=Krebs |first1=Robert E. |last2=Krebs |first2=Carolyn A. |date=2003 |title=Groundbreaking Scientific Experiments, Inventions, and Discoveries of the Ancient World |publisher=Greenwood Press |isbn=978-0-313-31342-4 |ref=none}}
* {{Citation |last=Laird |first=Edgar |date=1997 |title=Astrolabes and the Construction of Time in the Late Middle Ages |journal=Constructions of Time in the Late Middle Ages |editor=Carol Poster and Richard Utz |location= Evanston, Illinois |publisher= Northwestern University Press |pages=51–69 |ref=none}}
* {{Citation |editor1-first=Edgar |editor1-last=Laird |editor2-first=Robert |editor2-last=Fischer |location=Binghamton, New York |year= 1995 |title=Critical edition of Pélerin de Prusse on the Astrolabe (translation of ''Practique de Astralabe'') |journal=Medieval & Renaissance Texts & Studies |isbn= 0-86698-132-2 |ref=none}}
* {{Citation |last=Lewis |first=M. J. T. |date=2001 |title=Surveying Instruments of Greece and Rome |publisher=Cambridge University Press |isbn=978-0-511-48303-5}}
* {{Citation |last=Morrison |first=James E. |date=2007 |title=The Astrolabe |publisher=Janus |isbn=978-0-939320-30-1 |ref=none}}
* {{Citation |last=Neugebauer |first=Otto E. |author-link=Otto E. Neugebauer |year=1975 |title=A History of Ancient Mathematical Astronomy |publisher=Springer |isbn=978-3-642-61912-0}}
* {{Citation |last=North |first=John David |date=2005 |title=God's Clockmaker: Richard of Wallingford and the Invention of Time |publisher=Continuum International Publishing Group |isbn=978-1-85285-451-5}}

==External links==
{{Commons and category|Astrolabe|Astrolabes}}
{{EB1911 poster|Astrolabe}}
{{Wiktionary|astrolabe}}
* [https://alexboxer.com/astrolabe/ Interactive digital astrolabe by Alex Boxer]
* [http://www.astrosurf.com/spheres/as/astrolabe-en.htm A digital astrolabe (HTML5 and javascript)]
* [https://www.aramcoworld.com/Articles/May-2019/Astrolabe-Tech-Made-Not-So-Easy Astrolabe Tech Made ... Not So Easy]
* [http://www.eso.org/~ohainaut/bin/astrolabe.cgi paper astrolabe generator, from the ESO]
* [https://www.youtube.com/watch?v=UseE1P6Wmv0 "Hello World!" for the Astrolabe: The First Computer] Video of Howard Covitz's Presentation at Ignite Phoenix, June 2009. [http://www.slideshare.net/hcovitz/the-astrolabe-the-first-computer-or-hello-world-on-the-astrolabe Slides for Presentation] Licensed as [[by-nc-nd|Creative Commons by-nc-nd]].
* [http://www.ted.com/talks/tom_wujec_demos_the_13th_century_astrolabe.html Video of Tom Wujec demonstrating an astrolabe.] {{Webarchive|url=https://web.archive.org/web/20120323125206/http://www.ted.com/talks/tom_wujec_demos_the_13th_century_astrolabe.html |date=2012-03-23 }} Taken at [[TEDGlobal|TEDGlobal 2009]]. Includes clickable transcript. Licensed as [[by-nc-nd|Creative Commons by-nc-nd]].
* [https://web.archive.org/web/20170508124755/http://www.astrolabes.org/ Archive of James E. Morrison's extensive website on Astrolabes]
* [http://www.rogivue.com/xoops/modules/news/article.php?storyid=13 A working model of the Dr. Ludwig Oechslin's Astrolabium Galileo Galilei watch]
* [http://www.rogivue.com/xoops/modules/news/article.php?storyid=14 Ulysse Nardin Astrolabium Galilei Galileo: A Detailed Explanation]
* [http://www.mhs.ox.ac.uk/astrolabe/ Fully illustrated online catalogue of world's largest collection of astrolabes]
* [http://www.myastrolabe.org Mobile astrolabe and horologium]
* Medieval equal hour [https://www.abc.net.au/news/2011-11-09/one-man27s-trash-is-another27s-centuries-old-treasure/3654974 horary quadrant]
* {{citation|url=http://astro.berkeley.edu/~mhughes/Teaching_&_Outreach_files/astrolabe.pdf|archive-url=https://web.archive.org/web/20150617101751/http://w.astro.berkeley.edu/~mhughes/Teaching_%26_Outreach_files/astrolabe.pdf|archive-date=2015-06-17|title=A Beginner's Guide to Basic Construction and Use of the Astrolabe (using ruler, protractor and compasses)|access-date=2018-10-26|url-status=dead}}

{{Islamic astronomy}}
{{Greek astronomy}}
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[[Category:Analog computers]]
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