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It closely parallels the genesis of other [[Islamic science]]s in its assimilation of foreign material and the amalgamation of the disparate elements of that material to create a science. These included [[Indian astronomy|Indian]], [[Sassanid Empire|Sassanid]] and [[Hellenistic civilization|Hellenistic]] works in particular, which were translated and built upon.<ref name=Gingerich/> In turn, Islamic astronomy later had a significant influence on Indian<ref>{{citation|first=Virendra Nath|last=Sharma|year=1995|title=Sawai Jai Singh and His Astronomy|publisher=Motilal Banarsidass Publ.|isbn=8120812565|pages=8-10}}</ref> and [[Europe]]an<ref name=Saliba/> astronomy (see [[Latin translations of the 12th century]]) as well as [[Chinese astronomy]].<ref>{{citation|last=van Dalen|first=Benno|contribution=Islamic Astronomical Tables in China: The Sources for Huihui li|editor-last=Ansari|editor-first=S. M. Razaullah|year=2002|title=History of Oriental Astronomy|publisher=[[Springer Science+Business Media]]|isbn=1402006578|pages=19-32}}</ref>
A significant number of [[star]]s in the [[sky]], such as [[Aldebaran]] and [[Altair]], and astronomical terms such as [[alhidade]], [[azimuth]], and [[almucantar]], are still today recognized with [[List of Arabic star names|their Arabic names]].<ref>{{cite web|url=http://www.icoproject.org/star.html|title=Arabic Star Names|date=2007-05-01|accessdate=2008-01-24|publisher=Islamic Crescents' Observation Project}}</ref>
A large corpus of literature from Islamic astronomy remains today, numbering approximately 10,000 manuscripts scattered throughout the world, many of which have not been read or cataloged. Even so, a reasonably accurate picture of Islamic activity in the field of astronomy can be reconstructed.<ref>{{Harv|Ilyas|1997}}</ref>
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==ഇസ്ലാമു ജോതിശാസ്ത്രവും==
[[Islam]] has affected astronomy directly and indirectly. A major impetus for the flowering of astronomy in Islam came from religious observances, which presented an assortment of problems in mathematical astronomy, specifically in [[spherical geometry]].<ref name=Gingerich/>
===Background===
In the 7th century, both [[Christian]]s and [[Jew]]s observed holy days, such as [[Easter]] and [[Passover]], whose timing was determined by the [[phases of the moon]]. Both communities had confronted the fact that the approximately 29.5-day lunar months are not commensurable with the 365-day [[solar year]]. To solve the problem, Christians and Jews had adopted a scheme based on a discovery made in ''circa'' 430 BC by the [[Athenian]] astronomer [[Meton]]. In the 19-year [[Metonic cycle]], there were 12 years of 12 lunar months and seven years of 13 lunar months. The periodic insertion of a 13th month kept calendar dates in step with the seasons.<ref name=Gingerich/>
On the other hand, [[astronomer]]s used [[Ptolemy]]'s way to calculate the place of the [[moon]] and [[star]]s. The method Ptolemy used to solve [[spherical triangle]]s was a clumsy one devised late in the first century by [[Menelaus of Alexandria]]. It involved setting up two intersecting [[right triangle]]s; by applying [[Menelaus' theorem]] it was possible to solve one of the six sides, but only if the other five sides were known. To tell the time from the [[sun]]'s [[altitude]], for instance, repeated applications of Menelaus' theorem were required. For medieval Islamic astronomers, there was an obvious challenge to find a simpler [[trigonometric]] method.<ref name=Gingerich/>
===ജ്യോതിശാസ്ത്ര്ത്തോടുള്ള ഇസ്ലാമിക സമീപനം===
Islam advised [[Muslim]]s to find ways of using the stars. The [[Qur'an]] says: "And it is He who ordained the stars for you that you may be guided thereby in the darkness of the land and the sea."<ref>{{cite quran|6|97|style=ref}}</ref> On the basis of this advice Muslim began to find better observational and navigational instruments, thus most navigational stars today have Arabic names.<ref name=Gingerich/>
Other influences of the Qur'an on Islamic astronomy included its "insistence that the Universe is ruled by a single [[Physical law|set of laws]]" which was "rooted in the Islamic concept of ''[[Tawhid|tawhîd]]'', the unity of God", as well its "greater respect for [[empirical]] [[data]] than was common in the preceding Greek civilization" which inspired Muslims to place a greater emphasis on empirical [[observation]],<ref>{{citation|first=I. A.|last=Ahmad|title=The impact of the Qur'anic conception of astronomical phenomena on Islamic civilization|journal=Vistas in Astronomy|volume=39|issue=4|year=1995|pages=395-403}}</ref> in contrast to ancient [[Greek philosophers]] such as the [[Platonists]] and [[Aristotelianism|Aristotelians]] who expressed a general distrust towards the [[sense]]s and instead viewed [[reason]] alone as being sufficient to understanding nature. The Qur'an's insistence on observation, reason and [[contemplation]] ("see", "think" and "contemplate"), on the other hand, led Muslims to develop an early [[scientific method]] based on these principles, particularly empirical observation. [[Muhammad Iqbal]] writes:<ref>{{citation|first=I. A.|last=Ahmad|contribution=The Rise and Fall of Islamic Science: The Calendar as a Case Study|title=Faith and Reason: Convergence and Complementarity|publisher=[[Al Akhawayn University]]|date=June 3, 2002|url=http://images.agustianwar.multiply.com/attachment/0/RxbYbQoKCr4AAD@kzFY1/IslamicCalendar-A-Case-Study.pdf |accessdate=2008-01-31}}</ref>
{{quote|“The general empirical attitude of the Qur'an which engendered in its followers a feeling of reverence for the actual, and ultimately made them the founders of modern science. It was a great point to awaken the empirical spirit in an age that renounced the visible as of no value in men's search after God.”}}
There are also several [[cosmological]] verses in the [[Qur'an]] (610-632) which some modern writers have interpreted as foreshadowing the [[Metric expansion of space|expansion of the universe]] and possibly even the [[Big Bang]] theory:<ref>{{cite web|author=A. Abd-Allah|url=http://www.usc.edu/dept/MSA/quran/scislam.html|title=The Qur'an, Knowledge, and Science|publisher=[[University of Southern California]]|accessdate=2008-01-22}}</ref>
<blockquote>Don't those who reject faith see that the heavens and the earth were a single entity then We ripped them apart?<ref>{{cite quran|21|30|style=ref}}</ref></blockquote>
<blockquote>And the heavens We did create with Our Hands, and We do cause it to expand.{{cite quran|51|47|style=ref}}</blockquote>
Several [[hadith]]s attributed to [[Muhammad]] also show that he was generally opposed to [[astrology]] as well as [[superstition]] in general. An example of this is when an [[eclipse]] occurred during his son [[Ibrahim ibn Muhammad]]'s death, and rumours began spreading about this being God's personal condolence. Muhammad is said to have replied:<ref>{{citation|first=James A.|last=Michene|title=Islam: The Misunderstood Religion|journal=[[Reader's Digest]]|date=May 1955|pages=68-70}}</ref>
<blockquote>"An eclipse is a phenomenon of nature. It is foolish to attribute such things to the death or birth of a human being."</blockquote>
===ഇസ്ലാമിക നിയമങ്ങള്===
There are several rules in Islam which lead Muslims to use better astronomical calculations and [[observation]]s.
The first issue is the [[Islamic calendar]]. The [[Qur'an]] says: "The number of months in the sight of Allah is twelve (in a year) so ordained by Him the day He created the heavens and the earth; of them four are sacred; that is the straight usage."<ref>{{cite quran|9|36|style=ref}}</ref><ref name=Gingerich/> Therefore Muslims could not follow the [[Liturgical year|Christian]] or [[Hebrew calendar]]s and they thus had to develop a new one.
The other issue is moon sighting. Islamic months do not begin at the astronomical [[new moon]], defined as the time when the moon has the same [[celestial longitude]] as the sun and is therefore invisible; instead they begin when the thin [[crescent moon]] is first sighted in the western evening sky.<ref name=Gingerich/> The Qur'an says: "They ask you about the waxing and waning phases of the crescent moons, say they are to mark fixed times for mankind and [[Hajj]]."<ref>{{cite quran|2|189|style=ref}}</ref><ref>{{citation|url=http://www.almizan.org/Tafseer/Volume3/Baqarah47.asp|chapter=Volume 3: Surah Baqarah, Verse 189|author=Syed Mohammad Hussain Tabatabai|title=Tafsir al-Mizan|accessdate=2008-01-24}}</ref>
This led Muslims to find the phases of the moon in the sky, and their efforts led to new mathematical calculations and observational instruments, as well as a special science being formed specifically for moon sighting.<ref>{{cite web|url=http://www.chowk.com/site/articles/index.php?id=4026|title=The Science of Moon Sighting|author=Khalid Shaukat|date= September 23, 1997|accessdate=2008-01-24}}</ref>
Muslims are also expected to pray towards the [[Kaaba]] in [[Mecca]] and orient their [[mosque]]s in that direction. Thus they need to determine the direction of Mecca from a given location.<ref>{{cite quran|2|144|style=ref}}</ref><ref>{{cite quran|2|150|style=ref}}</ref> Another problem is the time of [[Salah]]. Muslims need to determine from [[celestial bodies]] the proper times for the prayers at [[sunrise]], at [[Noon|midday]], in the [[afternoon]], at [[sunset]], and in the [[evening]].<ref name=Gingerich/><ref name=Tabatabai>{{citation|url=http://www.almizan.org/Tafseer/Volume2/Baqarah32.asp|author=Syed Mohammad Hussain Tabatabai|work=Tafsir al-Mizan|chapter=Volume 2: Surah Baqarah, Verses 142-151|accessdate=2008-01-24}}</ref>
===Necessity of spherical geometry===
{{see also|Islamic mathematics}}
Predicting just when the crescent moon would become visible is a special challenge to Islamic mathematical astronomers. Although [[Ptolemy]]'s theory of the complex lunar motion was tolerably accurate near the time of the new moon, it specified the moon's path only with respect to the [[ecliptic]]. To predict the first visibility of the moon, it was necessary to describe its motion with respect to the [[horizon]], and this problem demands fairly sophisticated [[spherical geometry]]. Finding the direction of [[Mecca]] and the time of [[Salah]] are the reasons which led to Muslims developing spherical geometry. Solving any of these problems involves finding the unknown sides or angles of a triangle on the [[celestial sphere]] from the known sides and angles. A way of finding the time of day, for example, is to construct a triangle whose [[Vertex (geometry)|vertices]] are the [[zenith]], the north [[celestial pole]], and the sun's position. The observer must know the altitude of the sun and that of the pole; the former can be observed, and the latter is equal to the observer's [[latitude]]. The time is then given by the angle at the intersection of the [[Meridian (astronomy)|meridian]] (the [[Arc (geometry)|arc]] through the zenith and the pole) and the sun's hour circle (the arc through the sun and the pole).<ref name=Gingerich/><ref name=Tabatabai/>
==ചരിത്രം==
[[Pre-Islamic Arabia]]n knowledge of [[star]]s was [[empirical]]; their knowledge was what they observed regarding the rising and setting of stars. The rise of [[Islam]] is claimed to have provoked increased [[Arab]] thought in this field.<ref name=Dallal162>{{Harv|Dallal|1999|p=162}}</ref> The foundations of Islamic astronomy closely parallels the genesis of other Islamic sciences in its assimilation of foreign material and the amalgamation of the disparate elements of that material to create a science that was essentially Islamic. These include [[Indian astronomy|Indian]], [[Sassanid Empire|Sassanid]] and [[Hellenistic civilization|Hellenistic]] works which were [[translation|translated]] and built upon.
The science historian [[Donald Routledge Hill]] has divided the history of Islamic astronomy into the four following distinct time periods in its history:<ref name=Dallal162/>
*Assimilation and syncretisation of earlier Hellenistic, Indian and Sassanid astronomy ([[700]]—[[825]] [[Anno Domini|AD]])
*Vigorous investigation, and acceptance and modification to the [[Ptolemaic system]] ([[825]]—[[1025]] [[Anno Domini|AD]])
*Flourishing of a distinctive Islamic system of astronomy ([[1025]]—[[1450]] [[Anno Domini|AD]])
*Stagnation, where few significant contributions were made ([[1450]]—[[1900]] [[Anno Domini|AD]])
===610-700===
From the beginning Muslim community in Medina sight [[new moon]] to determine the lunar months especially Ramadan and holy days.
In approximately 638 A.D, [[Caliph]] [[Umar]] introduced a new lunar calendar which is known as [[lunar calendar]] was made on the basis of Islamic view point. This calendar has twelve lunar months, the beginnings of which are determined by the sighting of the crescent moon. This calendar is about 11 days shorter than the solar year. This calendar is still in use for religious purposes among Muslims.<ref name=Gingerich/><ref>[http://islam.about.com/cs/calendar/a/hijrah_calendar.htm What is the Hijrah Calendar?]</ref>
===700-825===
This period was most notably the period of assimilation and syncretisation of earlier Hellenistic, Indian and Sassanid astronomy occurred during the eighth and early ninth centuries.
====Impetus====
Historians point out several factors that fostered the growth of Islamic astronomy. The first was the proximity of the [[Muslim world]] to the world of ancient learning. Much of the ancient [[Greek language|Greek]], [[Sanskrit]] and [[Middle Persian]] texts were translated into [[Arabic]] during the ninth century. This process was enhanced by the tolerance towards scholars of other religions.<ref name=Gingerich>{{Harv|Gingerich|1986}}</ref>
Another impetus came from Islamic religious observances, which presented a host of problems in mathematical astronomy. In solving these religious problems the Islamic scholars went far beyond the Greek mathematical methods.<ref name=Gingerich/>
====Ancient influences and translation movement====
During this period, a number of [[Sanskrit]] and [[Middle Persian]] texts were first translated into [[Arabic language|Arabic]]. The most notable of the texts was ''Zij al-Sindhind'',<ref>This book is not related to al-Khwarizmi's ''Zij al-Sindh''. On ''zijes'', see {{Harv|Kennedy|1956}}</ref> based on the ''[[Surya Siddhanta]]'' and the works of [[Brahmagupta]], and translated by [[Muhammad al-Fazari]] and [[Yaqūb ibn Tāriq]] in 777. Sources indicate that the text was translated after an [[Indian astronomy|Indian astronomer]] visited the court of [[Caliph]] [[Al-Mansur]] in 770. The most notable Middle Persian text translated was the ''Zij al-Shah'', a collection of astronomical tables compiled in Sassanid Persia over two centuries.
Fragments of text during this period indicate that Arabs adopted the [[Trigonometric function|sine function]] (inherited from [[Indian mathematics|Indian trigonometry]]) instead of the [[chord]]s of [[Arc (geometry)|arc]] used in Hellenistic mathematics.<ref name=Dallal162/> Another Indian influence was an approximate formula used for [[time]]keeping by Muslim astronomers.<ref>{{Harv|King|2002|p=240}}</ref>
[[Image:Almagest.jpg|thumb|A page from Ptolemy's ''Almagest''.]]
Islamic interest in [[astronomy]] ran parallel to the interest in mathematics. Especially noteworthy in this regard was the ''[[Almagest]]'' (c. 150) of the [[Egyptians|Egyptian]] astronomer [[Ptolemy]] (c. 100-178). The ''Almagest'' was a landmark work in its field, assembling, as [[Euclid]]'s ''[[Euclid's Elements|Elements]]'' had previously done with geometrical works, all extant knowledge in the field of astronomy that was known to the author. This work was originally known as ''The Mathematical Composition'', but after it had come to be used as a text in astronomy, it was called ''The Great Astronomer''. The Islamic world called it ''The Greatest'' prefixing the Greek work ''megiste'' (greatest) with the article ''al-'' and it has since been known to the world as ''Al-megiste'' or, after popular use in [[Western world|Western]] translation, ''Almagest''.<ref>{{cite web|title=Greek Astronomy|url=http://www.ibiblio.org/expo/vatican.exhibit/exhibit/d-mathematics/Greek_astro.html |accessdate=2008-01-15}}</ref> though much of the ''Almagest'' was incorrect, even in premise, it remained a standard astronomical text in both the Islamic world and [[Europe]] until the [[Maragheh observatory|Maragha Revolution]] and [[Copernican Revolution]].<ref>{{cite web|url=http://www.daviddarling.info/encyclopedia/A/Almagest.html|title=Almagest|publisher=The Internet Encyclopedia of Science|accessdate=2008-01-15}}</ref> Ptolemy also produced other works, such as ''Optics'', ''[[Harmonica]]'', and some suggest he also wrote ''Tetrabiblon''.
The ''Almagest'' was a particularly unifying work for its exhaustive lists of [[sidereal]] phenomena. He drew up a list of chronological tables of [[Assyria]]n, [[Persian Empire|Persian]], [[Ancient Greece|Greek]], and [[Roman Empire|Roman]] kings for use in reckoning the lapse of time between known astronomical events and fixed dates. In addition to its relevance to calculating accurate calendars, it linked far and foreign cultures together by a common interest in the stars and astrology. The work of Ptolemy was replicated and refined over the years under [[Arab]], [[Persian people|Persian]] and other [[Muslim]] astronomers and astrologers.
===825-1025===
The period throughout the ninth, tenth and early eleventh centuries was one of vigorous investigation, in which the superiority of the [[Ptolemaic system]] of astronomy was accepted and significant contributions made to it. Astronomical research was greatly supported by the [[Abbasid]] [[caliph]] [[al-Mamun]]. [[Baghdad]] and [[Damascus]] became the centers of such activity. The caliphs not only supported this work [[financial]]ly, but endowed the work with formal prestige.<ref>{{MacTutor|id=Sinan|title=Abu Said Sinan ibn Thabit ibn Qurra|date=November 1999|accessdate=2008-01-15}}</ref>
[[Image:Abu Abdullah Muhammad bin Musa al-Khwarizmi.jpg|thumb|[[Muhammad ibn Mūsā al-Khwārizmī|Al-Khwarizmi]], the father of [[algebra]] and [[algorithm]]s, wrote the ''[[Zij]] al-Sindh''.]]
====Observational astronomy====
In [[observational astronomy]], the first major original Muslim work of astronomy was ''Zij al-Sindh'' by [[Muhammad ibn Mūsā al-Khwārizmī|al-Khwarizimi]] in 830. The work contains tables for the movements of the sun, the moon and the five planets known at the time. The work is significant as it introduced Indian and Ptolemaic concepts into Islamic sciences. This work also marked the turning point in Islamic astronomy. Hitherto, Muslim astronomers had adopted a primarily research approach to the field, translating works of others and learning already discovered knowledge. Al-Khwarizmi's work marked the beginning of non-traditional methods of study and calculations.<ref>{{Harv|Dallal|1999|p=163}}</ref>
In 850, [[Alfraganus|al-Farghani]] wrote ''Kitab fi Jawani'' ("''A compendium of the science of stars''"). The book primarily gave a summary of Ptolemic cosmography. However, it also corrected Ptolemy's ''Almagest'' based on findings of earlier Iranian astronomers. Al-Farghani gave revised values for the obliquity of the ecliptic, the precessional movement of the [[apogee]]s of the sun and the moon, and the circumference of the earth. The books were widely circulated through the Muslim world, and even translated into [[Latin]].<ref>{{Harv|Dallal|1999|p=164}}</ref>
[[Image:Book Al Sufi.jpg|thumb|left|[[Azophi]]'s ''[[Book of Fixed Stars]]''. The constellation pictured here is [[Sagittarius (constellation)|Sagittarius]].]]
[[Muhammad ibn Jābir al-Harrānī al-Battānī]] (Albatenius) (853-929) discovered that the direction of the Sun's [[Orbital eccentricity|eccentric]] was changing, which in modern astronomy is equivalent to the Earth moving in an [[elliptical orbit]] around the Sun.<ref>{{Harv|Singer|1959|p=151}} ([[cf.]] {{Harv|Zaimeche|2002}})</ref> His times for the [[new moon]], lengths for the [[solar year]] and [[sidereal year]], prediction of [[eclipse]]s, and work on the phenomenon of [[parallax]], carried astronomers "to the verge of [[relativity]] and the [[space age]]."<ref>{{Harv|Wickens|1976|}} ([[cf.]] {{Harv|Zaimeche|2002}})</ref> Around the same time, Yahya Ibn Abi Mansour carried out extensive observations and tests, and wrote the ''Al-[[Zij]] al-Mumtahan'', in which he completely revised the ''Almagest'' values.<ref>{{citation|title=23rd Annual Conference on the History of Arabic Science|date=October 2001|publisher=[[Aleppo]], [[Syria]]}} ([[cf.]] {{Harv|Zaimeche|2002}})</ref>
In the 10th century, [[al-Sufi]] (Azophi) carried out observations on the [[star]]s and described their [[position]]s, [[apparent magnitude|magnitude]]s, brightness, and [[colour]], and drawings for each constellation in his ''[[Book of Fixed Stars]]''. [[Ibn Yunus]] observed more than 10,000 entries for the sun's position for many years using a large [[astrolabe]] with a diameter of nearly 1.4 metres. His observations on [[eclipse]]s were still used centuries later in [[Simon Newcomb]]'s investigations on the motion of the moon, while his other observations inspired [[Laplace]]'s ''Obliquity of the Ecliptic'' and ''Inequalities of Jupiter and Saturn's''.<ref name=Zaimeche>{{Harv|Zaimeche|2002}}</ref>
[[Abu-Mahmud al-Khujandi]] relatively accurately computed the [[axial tilt]] to be 23°32'19" (23.53°),<ref>{{Citation|first=Richard P.|last=Aulie|year=1994|date=March 1994|title=Al-Ghazali Contra Aristotle: An Unforeseen Overture to Science In Eleventh-Century Baghdad|journal=Perpectives on Science and Christian Faith|volume=45|pages=26-46}} ([[cf.]] {{cite web|url=http://www.1001inventions.com/index.cfm?fuseaction=main.viewSection&intSectionID=441|title=References
|publisher=1001 Inventions|accessdate=2008-01-22}})</ref> which was a significant improvement over the Greek and Indian estimates of 23°51'20" (23.86°) and 24°,<ref>{{Harv|Saliba|2007}}</ref> and still very close to the modern measurement of 23°26' (23.44°).
In 1006, the [[Egypt]]ian astronomer [[Ali ibn Ridwan]] observed [[SN 1006]], the brightest [[supernova]] in recorded history, and left a detailed description of the temporary star. He says that the object was two to three times as large as the disc of [[Venus (planet)|Venus]] and about one-quarter the brightness of the [[Moon]], and that the star was low on the southern horizon. Monks at the [[Benedictine]] abbey at [[Abbey of St. Gall|St. Gall]] later corroborated bin Ridwan's observations as to magnitude and location in the sky.
====Early heliocentric models====
[[Jafar al Sadiq]] proposed the heliocentric theory, being the first to refute the theory of the sun having to movements.
In the late ninth century, [[Ja'far ibn Muhammad Abu Ma'shar al-Balkhi]] developed a planetary model which some have interpreted as a [[Heliocentrism|heliocentric model]]. This is due to his [[Orbit (disambiguation)|orbital revolutions]] of the planets being given as heliocentric revolutions rather than [[Geocentric model|geocentric]] revolutions, and the only known planetary theory in which this occurs is in the heliocentric theory. His work on planetary theory has not survived, but his astronomical data was later recorded by al-Hashimi, [[Abū Rayhān al-Bīrūnī]] and [[al-Sijzi]].<ref>[[Bartel Leendert van der Waerden]] (1987). "The Heliocentric System in Greek, Persian and Hindu Astronomy", ''Annals of the New York Academy of Sciences'' '''500''' (1), 525–545 [534-537].</ref>
In the tenth century, the [[Brethren of Purity]] published the ''[[Encyclopedia of the Brethren of Purity]]'', in which a heliocentric view of the universe is expressed in a section on [[cosmology]]:<ref>{{Harv|Nasr|1993|p=77}}</ref>
{{quote|"God has placed the Sun at the center of the Universe just as the capital of a country is placed in its middle and the ruler's palace at the center of the city."}}
In the early eleventh century, [[al-Biruni]] had met several Indian scholars who believed in a heliocentric system. In his ''Indica'', he discusses the theories on the [[Earth's rotation]] supported by [[Brahmagupta]] and other [[Indian astronomy|Indian astronomers]], while in his ''Canon Masudicus'', al-Biruni writes that [[Aryabhata]]'s followers assigned the first movement from east to west to the Earth and a second movement from west to east to the fixed stars. Al-Biruni also wrote that [[al-Sijzi]] also believed the Earth was moving and invented an [[astrolabe]] called the "Zuraqi" based on this idea:<ref name=Nasr>{{Harv|Nasr|1993|pp=135-136}}</ref>
{{quote|"I have seen the astrolabe called Zuraqi invented by Abu Sa'id Sijzi. I liked it very much and praised him a great deal, as it is based on the idea entertained by some to the effect that the motion we see is due to the Earth's movement and not to that of the sky. By my life, it is a problem difficult of solution and refutation. [...] For it is the same whether you take it that the Earth is in motion or the sky. For, in both cases, it does not affect the Astronomical Science. It is just for the physicist to see if it is possible to refute it."}}
In his ''Indica'', al-Biruni briefly refers to his work on the refutation of heliocentrism, the ''Key of Astronomy'', which is now lost:<ref name=Nasr/>
{{quote|"The most prominent of both modern and ancient astronomers have deeply studied the question of the moving earth, and tried to refute it. We, too, have composed a book on the subject called ''Miftah 'ilm al-hai'ah'' (''Key of Astronomy''), in which we think we have surpassed our predecessors, if not in the words, at all events in the matter."}}
====Beginning of astrophysics and celestial mechanics====
The eldest [[Banū Mūsā]] brother, [[Ja'far Muhammad ibn Mūsā ibn Shākir]] (9th century), made significant contributions to [[astrophysics]] and [[celestial mechanics]]. He was the first to hypothesize that the heavenly bodies and [[celestial spheres]] were subject to the same [[Physical law|laws of physics]] as [[Earth]], unlike the ancients who believed that the celestial spheres followed their own set of physical laws different from that of Earth.<ref>{{Harv|Saliba|1994a|p=116}}</ref>
In his ''Astral Motion'' and ''The Force of Attraction'', Muhammad ibn Musa proposed that there was a [[force]] of [[Gravitation|attraction]] between [[Astronomical object|heavenly bodies]],<ref>{{citation|first=K. A.|last=Waheed|year=1978|title=Islam and The Origins of Modern Science|page=27|publisher=Islamic Publication Ltd., [[Lahore]]}}</ref> foreshadowing [[Newton's law of universal gravitation]].<ref>{{Harv|Briffault|1938|p=191}}</ref>
[[Ibn al-Haytham]] (Alhacen), in his ''[[Book of Optics]]'' (1021), was the first to discover that the [[celestial spheres]] do not consist of [[solid]] matter, and he also discovered that the heavens are less dense than the air. These views were later repeated by [[Witelo]] and had a significant influence on the [[Copernican heliocentrism|Copernican]] and [[Tychonic system]]s of astronomy.<ref>{{Harv|Rosen|1985|pp=19-20 & 21}}</ref>
====Beginning of experimental astronomy====
In the tenth century, [[Muhammad ibn Jābir al-Harrānī al-Battānī]] (Albatenius) (853-929) introduced the idea of [[Experiment|testing]] "past observations by means of new ones".<ref>{{Harv|Huff|2003|p=57}}</ref> This led to the use of exacting [[empirical]] observations and experimental techniques by Muslim astronomers from the eleventh century onwards.<ref>{{Harv|Huff|2003|p=326}}</ref>
In the eleventh century, [[Abū Rayhān al-Bīrūnī]] introduced the [[Scientific method|experimental method]] into astronomy and was the first to conduct elaborate [[experiment]]s related to astronomical phenomena.<ref name=Zahoor/> He discovered the [[Milky Way]] [[galaxy]] to be a collection of numerous [[Nebula|nebulous]] [[star]]s.<ref>{{MacTutor Biography|id=Al-Biruni|title=Abu Rayhan Muhammad ibn Ahmad al-Biruni}}</ref> In [[Afghanistan]], he observed and described the [[solar eclipse]] on [[April 8]], [[1019]], and the [[lunar eclipse]] on [[September 17]], [[1019]], in detail, and gave the exact [[latitude]]s of the stars during the lunar eclipse.<ref name=Zahoor>{{cite web|author=Dr. A. Zahoor|year=1997|url=http://www.unhas.ac.id/~rhiza/saintis/biruni.html|title=Abu Raihan Muhammad al-Biruni|publisher=[[Hasanuddin University]]|archiveurl=
http://209.85.135.104/search?sourceid=navclient-ff&ie=UTF-8&q=cache%3Ahttp%3A%2F%2Fwww.unhas.ac.id%2F~rhiza%2Fsaintis%2Fbiruni.html
|archivedate=2008-01-18}}</ref>
===1025-1450===
During this period, a distinctive Islamic system of astronomy flourished. Within the Greek tradition and its successors it was traditional to separate mathematical astronomy (as typified by [[Ptolemy]]) from philosophical cosmology (as typified by [[Aristotle]]). Muslim scholars developed a program of seeking a physically real configuration (''hay'a'') of the universe, that would be consistent with both [[mathematics|mathematical]] and [[physics|physical]] principles. Within the context of this ''hay'a'' tradition, Muslim astronomers began questioning technical details of the [[Ptolemaic system]] of astronomy.<ref>{{Harv|Sabra|1998|pp=293-8}}</ref> Most of these criticisms, however, continued to follow the Ptolemaic astronomical [[paradigm]], remaining within the [[geocentrism|geocentric]] framework.<ref>{{cite web|author=Dennis Duke|url=http://people.scs.fsu.edu/~dduke/arabmars.html|title=Arabic Models for outer Planets and Venus|accessdate=2008-01-22}}</ref> As the historian of astronomy, [[A. I. Sabra]], noted:
{{quote|"All Islamic astronomers from [[Thabit ibn Qurra]] in the ninth century to [[Ibn al-Shatir]] in the fourteenth, and all natural philosophers from [[al-Kindi]] to [[Averroes]] and later, are known to have accepted what Kuhn has called the "two-sphere universe" ...—the Greek picture of the world as consisting of two spheres of which one, the [[celestial spheres|celestial sphere]] made up of a special element called [[Aether (classical element)|aether]], concentrically envelops the other, where the [[classical elements|four elements]] of earth, water, air, and fire reside."<ref>{{Harv|Sabra|1998|pp=317-18}}</ref>}}
Some Muslim astronomers, however, most notably [[Abū Rayhān al-Bīrūnī]] and [[Nasīr al-Dīn al-Tūsī]], discussed whether the Earth moved and considered how this might be consistent with astronomical computations and physical systems.<ref>{{Harv|Ragep|Teresi|Hart|2002}}</ref> Several other Muslim astronomers, most notably those following the [[Maragheh observatory|Maragha school]] of thought, developed non-Ptolemaic planetary models within a geocentric context that were later adapted in the [[Copernican heliocentrism|Copernican model]] in a [[heliocentrism|heliocentric]] context.
====Refutations of astrology====
The first [[Semantics|semantic]] distinction between astronomy and [[Islamic astrology|astrology]] was given by the [[Persian people|Persian]] astronomer [[Abū Rayhān al-Bīrūnī|Abu Rayhan al-Biruni]] in the 11th century,<ref>S. Pines (September 1964). "The Semantic Distinction between the Terms Astronomy and Astrology according to al-Biruni", ''Isis'' '''55''' (3): 343-349.</ref> though he himself refuted astrology in another work. The study of astrology was also refuted by other Muslim astronomers at the time, including [[al-Farabi]], [[Ibn al-Haytham]], [[Avicenna]] and [[Averroes]]. Their reasons for refuting astrology were both due to the methods used by astrologers being [[conjectural]] rather than [[empirical]] and also due to the views of astrologers conflicting with orthodox [[Islam]].<ref>{{Harv|Saliba|1994b|pp=60 & 67-69}}</ref>
====Astrophysics and celestial mechanics====
In [[astrophysics]] and [[celestial mechanics]], [[Abū Rayhān al-Bīrūnī]] described the Earth's [[gravitation]] as:<ref name=Khwarizm/>
{{quote|"The attraction of all things towards the centre of the earth."}}
Al-Biruni also discovered that gravity exists within the [[Astronomical object|heavenly bodies]] and [[celestial spheres]], and he criticized the [[Aristotelian theory of gravity|Aristotelian]] views of them not having any [[levity]] or gravity and of [[circular motion]] being an [[Intrinsic and extrinsic properties|innate property]] of the heavenly bodies.<ref>{{Harv|Iqbal|Berjak|2003}}</ref>
In 1121, [[al-Khazini]], in his treatise ''The Book of the Balance of Wisdom'', states:<ref name=Zaimeche7>{{Harv|Zaimeche|2002|p=7}}</ref>
{{quote|"For each heavy body of a known weight positioned at a certain distance from the centre of the universe, its gravity depends on the remoteness from the centre of the universe. For that reason, the gravities of bodies relate as their distances from the centre of the universe."}}
Al-Khazini was thus the first to propose the theory that the [[Gravitation|gravities]] of bodies vary depending on their distances from the centre of the Earth. This phenomenon was not proven until [[Newton's law of universal gravitation]] in the 18th century.<ref name=Zaimeche7/>
====Beginning of hay'a tradition====
[[Image:Ibn haithem portrait.jpg|thumb|[[Ibn al-Haytham]] (Alhacen) was a pioneer of the Muslim ''haya'' tradition of astronomy, presented the first critique and reform of [[Ptolemy]]'s model, and laid the theoretical foundations for modern [[telescope|telescopic]] astronomy.]]
Between 1025 and 1028, [[Ibn al-Haytham]] ([[Latin]]ized as Alhazen), began the ''hay'a'' tradition of Islamic astronomy with his ''Al-Shuku ala Batlamyus'' (''Doubts on Ptolemy''). While maintaining the physical reality of the [[geocentric model]], he was the first to criticise [[Ptolemy]]'s astronomical system, which he criticised on [[empirical]], [[observation]]al and [[experiment]]al grounds,<ref>{{Harv|Sabra|1998|p=300}}</ref> and for relating actual physical motions to imaginary mathematical points, lines and circles:
{{quote|"Ptolemy assumed an arrangement that cannot exist, and the fact that this arrangement produces in his imagination the motions that belong to the planets does not free him from the error he committed in his assumed arrangement, for the existing motions of the planets cannot be the result of an arrangement that is impossible to exist."<ref>{{citation|url=http://setis.library.usyd.edu.au/stanford/entries/copernicus/index.html
|contribution=Nicolaus Copernicus|title=[[Stanford Encyclopedia of Philosophy]]|year=2004|accessdate=2008-01-22}}</ref>}}
Ibn al-Haytham developed a physical structure of the Ptolemaic system in his ''Treatise on the configuration of the World'', or ''Maqâlah fî ''hay'at'' al-‛âlam'', which became an influential work in the ''hay'a'' tradition.<ref>{{Harv|Langermann|1990|pp=25-34}}</ref> In his ''Epitome of Astronomy'', he insisted that the heavenly bodies "were accountable to the [[Physical law|laws of physics]]."<ref>{{Harv|Duhem|1969|p=28}}</ref> The foundations of [[telescope|telescopic]] astronomy can also be traced back to Ibn al-Haytham, due to the influence of his [[Optics|optical]] studies on the later development of the modern telescope.<ref>{{Harv|Marshall|1950}}</ref>
In 1038, Ibn al-Haytham described the first non-Ptolemaic configuration in ''The Model of the Motions''. His reform was not concerned with [[cosmology]], as he developed a systematic study of celestial [[kinematics]] that was completely [[geometry|geometric]]. This in turn led to innovative developments in [[infinitesimal]] [[geometry]].<ref>{{Harv|Rashed|2007}}</ref> His reformed model was the first to reject the [[equant]]<ref>{{Harv|Rashed|2007|pp=20 & 53}}</ref> and [[eccentricity|eccentrics]],<ref>{{Harv|Rashed|2007|pp=33-4}}</ref> separate [[natural philosophy]] from astronomy, free celestial kinematics from cosmology, and reduce physical entities to geometrical entities. The model also propounded the [[Earth's rotation]] about its axis,<ref>{{Harv|Rashed|2007|pp=20 & 32-33}}</ref> and the centres of motion were geometrical points without any physical significance, like [[Johannes Kepler]]'s model centuries later.<ref>{{Harv|Rashed|2007|pp=51-2}}</ref> Ibn al-Haytham also describes an early version of [[Occam's razor]], where he employs only minimal hypotheses regarding the properties that characterize astronomical motions, as he attempts to eliminate from his planetary model the [[cosmology|cosmological]] hypotheses that cannot be observed from [[Earth]].<ref>{{Harv|Rashed|2007|pp=35-6}}</ref>
[[Image:Abu-Rayhan Biruni 1973 Afghanistan post stamp.jpg|thumb|left|[[Abū al-Rayhān al-Bīrūnī|Al-Biruni]] was the first to conduct elaborate [[experiment]]s related to astronomical phenomena, and he introduced the analysis of the [[acceleration]] of planets, discovered that the motions of the [[Apsis|solar apogee]] and [[precession]] are not identical, discussed the possibility of [[heliocentrism]], and suggested that the [[Earth's rotation]] on its axis would be consistent with his astronomical parameters.]]
====Early alternative models====
In 1030, [[Abū al-Rayhān al-Bīrūnī]] discussed the [[Indian astronomy|Indian planetary theories]] of [[Aryabhata]], [[Brahmagupta]] and [[Varahamihira]] in his ''Ta'rikh al-Hind'' (Latinized as ''Indica''). Biruni stated that [[Brahmagupta]] and others consider that the [[Earth's rotation|earth rotates]] on its axis and Biruni noted that this does not create any mathematical problems.<ref>{{Harv|Nasr|1993|p=135, n. 13}}</ref>
Abu Said [[al-Sijzi]], a contemporary of al-Biruni, suggested the possible heliocentric movement of the Earth around the Sun, which al-Biruni did not reject.<ref name=Baker>{{Harv|Baker|Chapter|2002}}</ref> Al-Biruni agreed with the [[Earth's rotation]] about its own axis, and while he was initially neutral regarding the [[heliocentrism|heliocentric]] and [[geocentric model]]s,<ref>{{Harv|Marmura|1965}}</ref> he considered heliocentrism to be a philosophical problem.<ref name=Saliba/> He remarked that if the Earth rotates on its axis and moves around the Sun, it would remain consistent with his astronomical parameters:<ref name=Khwarizm/><ref>G. Wiet, V. Elisseeff, P. Wolff, J. Naudu (1975). ''History of Mankind, Vol 3: The Great medieval Civilisations'', p. 649. George Allen & Unwin Ltd, [[UNESCO]].</ref>
{{quote|"Rotation of the earth would in no way invalidate astronomical calculations, for all the astronomical data are as explicable in terms of the one theory as of the other. The problem is thus difficult of solution."}}
In 1031, al-Biruni completed his extensive astronomical encyclopaedia ''Kitab al-Qanun al-Mas'udi'' ([[Latin]]ized as ''Canon Mas’udicus''),<ref name=Covington>{{Harv|Covington|2007}}</ref> in which he recorded his astronomical findings and formulated astronomical tables. In it he presented a geocentric model, tabulating the distance of all the [[celestial spheres]] from the central Earth, computed according to the principles of Ptolemy's ''[[Almagest]]''.<ref>{{Harv|Nasr|1993|p=134}}</ref> The book introduces the mathematical technique of analysing the [[acceleration]] of the planets, and first states that the motions of the [[Apsis|solar apogee]] and the [[precession]] are not identical. Al-Biruni also discovered that the distance between the Earth and the Sun is larger than [[Ptolemy]]'s estimate, on the basis that Ptolemy disregarded the annual [[solar eclipse]]s.<ref name=Khwarizm>{{cite web|url=http://muslimheritage.com/topics/default.cfm?ArticleID=482|title=Khwarizm|publisher=Foundation for Science Technology and Civilisation|accessdate=2008-01-22}}</ref><ref>{{Harv|Saliba|1980|p=249}}</ref>
In 1070, [[Juzjani, Abu Ubaid|Abu Ubayd al-Juzjani]], a pupil of [[Avicenna]], proposed a non-Ptolemaic configuration in his ''Tarik al-Aflak''. In his work, he indicated the so-called "[[equant]]" problem of the Ptolemic model, and proposed a solution for the problem. He claimed that his teacher Avicenna had also worked out the equant problem.<ref>{{Harv|Sabra|1998|pp=305-306}}</ref>
====Andalusian Revolt====
[[Image:AverroesColor.jpg|thumb|[[Averroes]] rejected the [[Deferent and epicycle|eccentric deferents]] introduced by [[Ptolemy]]. He rejected the [[Ptolemaic model]] and instead argued for a strictly [[concentric]] model of the universe.]]
In the 11th-12th centuries, astronomers in [[al-Andalus]] took up the challenge earlier posed by Ibn al-Haytham, namely to develop an alternate non-Ptolemaic configuration that evaded the errors found in the [[Geocentric model|Ptolemaic model]].<ref>{{Harv|Saliba|1981|p=219}}</ref> Like Ibn al-Haytham's critique, the anonymous Andalusian work, ''al-Istidrak ala Batlamyus'' (''Recapitulation regarding Ptolemy''), included a list of objections to Ptolemic astronomy. This marked the beginning of the Andalusian school's [[revolt]] against Ptolemaic astronomy, otherwise known as the "Andalusian Revolt".<ref>{{citation|first=A. I.|last=Sabra|author-link=A. I. Sabra|contribution=The Andalusian Revolt Against Ptolemaic Astronomy: Averroes and al-Bitrûjî|pages=233-53|editor-first=Everett|editor-last=Mendelsohn|title=Transformation and Tradition in the Sciences: Essays in honor of I. Bernard Cohen|publisher=[[Cambridge University Press]]}}</ref>
In the late 11th century, [[Arzachel|al-Zarqali]] (Latinized as Arzachel) discovered that the orbits of the planets are [[elliptic orbit]]s and not circular orbits,<ref>[[Robert Briffault]] (1938). ''The Making of Humanity'', p. 190.</ref> though he still followed the Ptolemaic model.
In the 12th century, [[Averroes]] rejected the [[Deferent and epicycle|eccentric deferents]] introduced by [[Ptolemy]]. He rejected the [[Ptolemaic model]] and instead argued for a strictly [[concentric]] model of the universe. He wrote the following criticism on the Ptolemaic model of planetary motion:<ref name=Gingerich/>
{{quote|"To assert the existence of an eccentric sphere or an epicyclic sphere is contrary to nature. [...] The astronomy of our time offers no truth, but only agrees with the calculations and not with what exists."}}
Averroes' contemporary, [[Maimonides]], wrote the following on the planetary model proposed by [[Ibn Bajjah]] (Avempace):
{{quote|"I have heard that Abu Bakr [Ibn Bajja] discovered a system in which no [[Deferent and epicycle|epicycles]] occur, but [[Eccentricity|eccentric]] spheres are not excluded by him. I have not heard it from his pupils; and even if it be correct that he discovered such a system, he has not gained much by it, for eccentricity is likewise contrary to the principles laid down by Aristotle.... I have explained to you that these difficulties do not concern the astronomer, for he does not profess to tell us the existing properties of the spheres, but to suggest, whether correctly or not, a theory in which the motion of the stars and planets is uniform and circular, and in agreement with observation."<ref>Bernard R. Goldstein (March 1972). "Theory and Observation in Medieval Astronomy", ''Isis'' '''63''' (1): 39-47 [40-41].</ref>}}
Later in the 12th century, Ibn Bajjah's successors, [[Ibn Tufail]] (Abubacer) and [[Nur Ed-Din Al Betrugi|al-Betrugi]] (Alpetragius), were the first to propose planetary models without any [[equant]], [[Deferent and epicycle|epicycles or eccentrics]]. Al-Betrugi was also the first to discover that the planets are [[Luminosity|self-luminous]].<ref>Bernard R. Goldstein (March 1972). "Theory and Observation in Medieval Astronomy", ''Isis'' '''63''' (1): 39-47 [41].</ref> Their configurations, however, were not accepted due to the numerical predictions of the planetary positions in their models being less accurate than that of the Ptolemaic model,<ref name=Gale>{{citation|url=http://www.bookrags.com/research/ptolemaic-astronomy-islamic-planeta-scit-021234
|contribution=Ptolemaic Astronomy, Islamic Planetary Theory, and Copernicus's Debt to the Maragha School|title=Science and Its Times|publisher=[[Thomson Gale]]|year=2005-2006|accessdate=2008-01-22}}</ref> mainly because they followed [[Aristotle]]'s notion of perfect circular motion.
====Maragha Revolution====
{{main|Maragheh observatory}}
The "Maragha Revolution" refers to the [[Maragheh]] school's [[revolution]] against Ptolemaic astronomy. The "Maragha school" was an astronomical tradition beginning in the [[Maragheh observatory]] and continuing with astronomers from [[Damascus]] and [[Samarkand]]. Like their Andalusian predecessors, the Maragha astronomers attempted to solve the [[equant]] problem and produce alternative configurations to the [[Ptolemaic model]]. They were more successful than their Andalusian predecessors in producing non-Ptolemaic configurations which eliminated the equant and eccentrics, were more accurate than the Ptolemaic model in numerically predicting planetary positions, and were in better agreement with [[empirical]] [[observation]]s.<ref name=Saliba-1994>{{Harv|Saliba|1994b|pp=233-234 & 240}}</ref> The most important of the Maragha astronomers included [[Mo'ayyeduddin Urdi]] (d. 1266), [[Nasīr al-Dīn al-Tūsī]] (1201-1274), 'Umar al-Katibi al-[[Qazwini]] (d. 1277), [[Qutb al-Din al-Shirazi]] (1236-1311), Sadr al-Sharia al-Bukhari (c. 1347), [[Ibn al-Shatir]] (1304-1375), [[Ali al-Qushji]] (c. 1474), [[al-Birjandi]] (d. 1525) and Shams al-Din al-Khafri (d. 1550).<ref>{{Harv|Dallal|1999|p=171}}</ref>
[[Image:Al-Tusi Nasir.jpeg|thumb|left|150px|[[Nasīr al-Dīn al-Tūsī]] resolved significant problems in the [[Geocentric model|Ptolemaic system]] with the [[Tusi-couple]], which later played an important role in the [[Copernican heliocentrism|Copernican model]].]]
Some have described their achievements in the 13th and 14th centuries as a "Maragha Revolution", "Maragha School Revolution", or "[[Scientific Revolution]] before the [[Renaissance]]". An important aspect of this revolution included the realization that astronomy should aim to describe the behaviour of [[Physical body|physical bodies]] in [[Islamic mathematics|mathematical]] language, and should not remain a mathematical [[hypothesis]], which would only save the [[phenomena]]. The Maragha astronomers also realized that the [[On the Heavens|Aristotelian]] view of [[Motion (physics)|motion]] in the universe being only circular or [[linear]] was not true, as the [[Tusi-couple]] showed that linear motion could also be produced by applying [[circular motion]]s only.<ref>{{Harv|Saliba|1994b|pp=245, 250, 256-257}}</ref>
Unlike the ancient Greek and Hellenistic astronomers who were not concerned with the coherence between the mathematical and physical principles of a planetary theory, Islamic astronomers insisted on the need to match mathematics with the real world surrounding them,<ref>{{citation|first=George|last=Saliba|author-link=George Saliba|date=Autumn 1999|title=Seeking the Origins of Modern Science?|journal=BRIIFS|volume=1|issue=2|url=http://www.riifs.org/review_articles/review_v1no2_sliba.htm |accessdate=2008-01-25}}</ref> which gradually evolved from a reality based on [[Aristotelian physics]] to one based on an empirical and mathematical [[physics]] after the work of Ibn al-Shatir. The Maragha Revolution was thus characterized by a shift away from the philosophical foundations of [[On the Heavens|Aristotelian cosmology]] and [[Ptolemaic astronomy]] and towards a greater emphasis on the empirical observation and [[Islamic mathematics|mathematization]] of astronomy and of [[nature]] in general, as exemplified in the works of Ibn al-Shatir, al-Qushji, al-Birjandi and al-Khafri.<ref>{{Harv|Saliba|1994b|pp=42 & 80}}</ref><ref>{{citation|first=Ahmad|last=Dallal|year=2001-2002|title=The Interplay of Science and Theology in the Fourteenth-century Kalam|publisher=From Medieval to Modern in the Islamic World, Sawyer Seminar at the [[University of Chicago]] |url=http://humanities.uchicago.edu/orgs/institute/sawyer/archive/islam/dallal.html |accessdate=2008-02-02}}</ref><ref>{{Harv|Huff|2003|pp=217-8}}</ref>
Other achievements of the Maragha school include the first empirical observational evidence for the [[Earth's rotation]] on its axis by al-Tusi and al-Qushji,<ref name=Ragep/> the separation of [[natural philosophy]] from astronomy by Ibn al-Shatir and al-Qushji,<ref name=Ragep2>{{Harv|Ragep|2001b}}</ref> the rejection of the Ptolemaic model on empirical rather than [[philosophical]] grounds by Ibn al-Shatir,<ref name=Saliba-1994/> and the development of a non-Ptolemaic model by Ibn al-Shatir that was mathematically identical to the [[Copernican heliocentrism|heliocentric Copernical model]].<ref>{{Harv|Saliba|1994b|pp=254 & 256-257}}</ref>
[[Image:Ghotb2.jpg|thumb|Medieval manuscript by [[Qutb al-Din al-Shirazi]] depicting an epicyclic planetary model.]]
[[Mo'ayyeduddin Urdi]] (d. 1266) was the first of the Maragheh astronomers to develop a non-Ptolemaic model, and he proposed a new theorem, the "Urdi lemma".<ref>{{Harv|Saliba|1979}}</ref> [[Nasīr al-Dīn al-Tūsī]] (1201-1274) resolved significant problems in the Ptolemaic system by developing the [[Tusi-couple]] as an alternative to the physically problematic [[equant]] introduced by Ptolemy,<ref name=Gill>{{Harv|Gill|2005}}</ref> and conceived a plausible model for [[ellipse|elliptical]] orbits.<ref name=Covington/> Tusi's student [[Qutb al-Din al-Shirazi]] (1236-1311), in his ''The Limit of Accomplishment concerning Knowledge of the Heavens'', discussed the possibility of [[heliocentrism]]. 'Umar al-Katibi al-[[Qazwini]] (d. 1277), who also worked at the Maragheh observatory, in his ''Hikmat al-'Ain'', wrote an argument for a heliocentric model, though he later abandoned the idea.<ref name=Baker/>
[[Ibn al-Shatir]] ([[1304]]–[[1375]]) of [[Damascus]], in ''A Final Inquiry Concerning the Rectification of Planetary Theory'', incorporated the Urdi lemma, and eliminated the need for an equant by introducing an extra epicycle (the Tusi-couple), departing from the Ptolemaic system in a way that was mathematically identical to what [[Nicolaus Copernicus]] did in the 16th century. Unlike previous astronomers before him, Ibn al-Shatir was not concerned with adhering to the theoretical principles of [[natural philosophy]] or Aristotelian [[cosmology]], but rather to produce a model that was more consistent with [[empirical]] observations. His model was thus in better agreement with empirical [[observation]]s than any previous model,<ref name=Saliba-1994/> and was also the first that permitted empirical [[Experiment|testing]].<ref>Y. M. Faruqi (2006). "Contributions of Islamic scholars to the scientific enterprise", ''International Education Journal'' '''7''' (4): 395-396.</ref> His work thus marked a turning point in astronomy, which may be considered a "Scientific Revolution before the Renaissance".<ref name=Saliba-1994/> His rectified model was later adapted into a [[Copernican heliocentrism|heliocentric model]] by Copernicus,<ref name=Gill/> which was mathematically achieved by reversing the direction of the last vector connecting the Earth to the Sun.<ref name=Saliba>{{Harv|Saliba|1999}}</ref> In the published version of his masterwork, ''[[De revolutionibus orbium coelestium]]'', Copernicus also cites the theories of [[al-Battani]], [[Arzachel]] and [[Averroes]] as influences,<ref name=Covington/> while the works of [[Ibn al-Haytham]] and [[al-Biruni]] were also known in Europe at the time.
An area of active discussion in the Maragheh school, and later the [[Samarkand]] and [[Istanbul]] observatories, was the possibility of the [[Earth's rotation]]. Supporters of this theory included [[Nasīr al-Dīn al-Tūsī]], Nizam al-Din al-Nisaburi (c. 1311), al-Sayyid al-Sharif al-Jurjani (1339-1413), Ali al-Qushji (d. 1474), and Abd al-Ali [[al-Birjandi]] (d. 1525). Al-Tusi was the first to present empirical observational evidence of the Earth's rotation, using the location of [[comet]]s relevant to the Earth as evidence, which al-Qushji elaborated on with further empirical observations while rejecting Aristotelian [[natural philosophy]] altogether. Both of their arguments were similar to the arguments later used by [[Nicolaus Copernicus]] in 1543 to explain the Earth's rotation.<ref name=Ragep>{{Harv|Ragep|2001a}}</ref>
===1450-1900===
This period was considered the period of stagnation, when the traditional system of astronomy continued to be practised with enthusiasm, but with decreasing innovation.<ref name=Dallal162/> It was believed there was no innovation of major significance during this period, but this view has been rejected by historians of astronomy in recent times, who argue that Muslim astronomers continued to make significant advances in astronomy through to the 16th century and possibly after this as well.<ref name=Ragep2/><ref name=Saliba-2000/> After the 16th century, there appears to have been little concern for [[Astrophysics|theoretical astronomy]], but [[observational astronomy]] in the Islamic tradition continued in the three Muslim [[Gunpowder warfare|gunpowder empires]]: the [[Ottoman Empire]], the [[Safavid dynasty]] of Persia, and the [[Mughal Empire]] of India.
====Earth's motion====
[[Image:Ali Kuşçu Portre.jpg|right|thumb|[[Ali Kuşçu|Ali al-Qushji]] provided [[empirical]] evidence for the [[Earth's rotation|Earth's motion]] and completely separated astronomy from [[natural philosophy]].]]
The work of [[Ali Kuşçu|Ali al-Qushji]] (d. 1474), who worked at [[Samarkand]] and then [[Istanbul]], is seen as a late example of innovation in Islamic astronomy and it is believed he may have had an influence on [[Nicolaus Copernicus]] due to similar arguments concerning the [[Earth's rotation]]. Before al-Qushji, the only astronomer to present an [[Empiricism|empirical]] argument for the Earth's rotation was [[Nasīr al-Dīn al-Tūsī]] (d. 1274), who used the phenomena of [[comet]]s to refute [[Ptolemy]]'s claim that a stationery Earth can be determined through observation alone. Al-Tusi, however, accepted that the Earth was stationery on the basis of [[natural philosophy]] instead, particularly [[On the Heavens|Aristotelian cosmology]]. In the 15th century, the influence of [[Aristotelian physics]] and natural philosophy was declining due to religious opposition. Al-Qushji, in his ''Concerning the Supposed Dependence of Astronomy upon Philosophy'', thus rejected Aristotelian physics and completely separated natural philosophy from astronomy, allowing astronomy to become a purely empirical and mathematical science. This allowed him to explore alternatives to the Aristotelian notion of a stationery Earth, as he explored the idea of a moving Earth. He elaborated on al-Tusi's argument and concluded, on the basis of [[empiricism]] rather than speculative philosophy, that the moving Earth theory is just as likely to be true as the stationary Earth theory and that it is not possible to [[empirical]]ly deduce which theory is true.<ref name=Ragep/><ref name=Ragep2/><ref>Edith Dudley Sylla, "Creation and nature", in Arthur Stephen McGrade (2003), pp. 178-179, [[Cambridge University Press]], ISBN 0521000637.</ref> Ali al-Qushji also improved on al-Tusi's planetary model and presented an alternative planetary model for [[Mercury (planet)|Mercury]].<ref>{{citation|last=Saliba|first=George|author-link=George Saliba|title=Arabic planetary theories after the eleventh century AD|pages=123-4}}, in {{Harv|Rashed|Morelon|1996|pp=58-127}}</ref>
In the 16th century, the debate on the Earth's motion was continued by [[al-Birjandi]] (d. 1528), who in his analysis of what might occur if the Earth were rotating, develops a hypothesis similar to [[Galileo Galilei]]'s notion of "circular [[inertia]]",<ref>{{Harv|Ragep|2001b|pp=63-4}}</ref> which he described in the following observational test (as a response to one of [[Qutb al-Din al-Shirazi]]'s arguments):
{{quote|"The small or large rock will fall to the Earth along the path of a line that is perpendicular to the plane (''sath'') of the horizon; this is witnessed by experience (''tajriba''). And this perpendicular is away from the tangent point of the Earth’s sphere and the plane of the perceived (''hissi'') horizon. This point moves with the motion of the Earth and thus there will be no difference in place of fall of the two rocks."<ref>{{Harv|Ragep|2001a|pp=152-3}}</ref>}}
====Theoretical astronomy====
It was traditionally believed that Islamic astronomers made no more advances in planetary theory after the work of [[Ibn al-Shatir]] in the 14th century, but recent studies have shown that there were several significant advances in planetary theory through to the 16th century, after [[George Saliba]] studied the works of a 16th century astronomer, Shams al-Din al-Khafri (d. 1550), a [[Safavid]] commentator on earlier [[Maragheh observatory|Maragha astronomers]]. Saliba wrote the following on al-Khafri's work:
{{quote|"By his sheer insight into the role of mathematics in describing natural phenomena, this astronomer managed to bring the hay'a tradition to such unparalleled heights that could not be matched anywhere else in the world at that time neither mathematically nor astronomically. By working on the alternative mathematical models that could replace those of Ptolemy, and by scrutinizing the works of his predecessors who were all searching for unique mathematical models that could describe the physical phenomena consistently, this astronomer finally realized that all mathematical modeling had no physical truth by itself and was simply another language with which one could describe the physical observed reality. He also realized that the specific phenomena that were being described by the Ptolemaic models did not have unique mathematical solutions that were subject to the same restraints. Rather there were several mathematical models that could account for the Ptolemaic observations, yield identical predictive results at the same critical points used by Ptolemy to construct his own models (thus accounting for the observations as perfectly as Ptolemy could) and still meet the consistency requirement that was imposed by the Aristotelian cosmology which was adopted by the writers in the ''hay'a'' tradition."<ref name=Saliba-2000>{{Harv|Saliba|2000}}</ref>}}
====Observational astronomy====
Another notable 16th century Muslim astronomer was the [[Ottoman Empire|Ottoman]] astronomer [[Taqi al-Din]], who built the [[Istanbul observatory of al-Din]] in 1577, where he carried out astronomical observations until 1580. He produced a [[Zij]] (named ''Unbored Pearl'') and [[astronomical catalog]]ues that were more accurate than those of his contemporaries, [[Tycho Brahe]] and [[Nicolaus Copernicus]]. Taqi al-Din was also the first astronomer to employ a [[Decimal separator|decimal point]] notation in his [[observation]]s rather than the [[sexagesimal]] fractions used by his contemporaries and predecessors.<ref name=Tekeli>Sevim Tekeli, "Taqi al-Din", in Helaine Selin (1997), ''Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures'', [[Kluwer Academic Publishers]], ISBN 0792340663.</ref> After the destruction of the Istanbul observatory of al-Din in 1580, however, astronomical activity stagnated in the Ottoman Empire, until the introduction of [[Copernican heliocentrism]] in 1660, when the Ottoman scholar Ibrahim Efendi al-Zigetvari Tezkireci translated Noël Duret's French astronomical work (written in 1637) into Arabic.<ref>{{citation|last=Zaken|first=Avner Ben|year=2004|title=The heavens of the sky and the heavens of the heart: the Ottoman cultural context for the introduction of post-Copernican astronomy|journal=The British Journal for the History of Science|publisher=[[Cambridge University Press]]|volume=37|pages=1-28}}</ref>
[[Image:Heliocentric.jpg|thumb|right|A model of the [[Copernican heliocentrism|heliocentric system]] attributed to [[Nicolaus Copernicus]].]]
Meanwhile in the [[Mughal Empire]], the 16th and 17th centuries saw a synthesis between Islamic and [[Indian astronomy]], where Islamic observational techniques and instruments were combined with [[Indian mathematics|Hindu computational]] techniques. While there appears to have been little concern for theoretical astronomy, Muslim and [[Hindu]] astronomers in [[History of India|India]] continued to make advances in [[observational astronomy]] and produced nearly a hundred Zij treatises. [[Humayun]] built a personal observatory near [[Delhi]], while [[Jahangir]] and [[Shah Jahan]] were also intending to build observatories but were unable to do so. After the decline of the Mughal Empire, however, it was a Hindu king, [[Jai Singh II of Amber]], who attempted to revive the Islamic tradition of astronomy in India. In the early 18th century, he built several large observatories in order to rival the famous Samarkand observatory, and in order to update [[Ulugh Beg]]'s ''[[Zij-i-Sultani]]'' with more accurate observations. The instruments and observational techniques used at the observatory were mainly derived from the Islamic tradition, and the computational techniqes from the Hindu tradition.<ref name=Sharma>{{citation|title=Sawai Jai Singh and His Astronomy|first=Virendra Nath|last=Sharma|year=1995|publisher=[[Motilal Banarsidass]] Publ.|isbn=8120812565|pages=8-9}}</ref><ref name=Baber>{{citation|title=The Science of Empire: Scientific Knowledge, Civilization, and Colonial Rule in India|first=Zaheer|last=Baber|year=1996|publisher=[[State University of New York Press]]|isbn=0791429199|pages=82-9}}</ref> In particular, one of the most remarkable astronomical instruments invented by Muslims in Mughal India is the seamless celestial globe (see [[#Globes|Globes]] below).
Jai Singh also invited European [[Jesuit]] astronomers to his observatory, who had bought back the astronomical tables compiled by [[Philippe de La Hire]] in 1702. After examining La Hire's work, Jai Singh concluded that the techniques and instruments used in the European tradition were inferior to the Islamic and Indian traditions. It is uncertain whether Islamic astronomers in India were aware of the [[Copernican Revolution]] via the Jesuits, but it appears they were not concerned with theoretical astronomy, hence the theoretical advances in Europe did not interest them at the time.<ref>{{citation|title=The Science of Empire: Scientific Knowledge, Civilization, and Colonial Rule in India|first=Zaheer|last=Baber|year=1996|publisher=[[State University of New York Press]]|isbn=0791429199|pages=89-90}}</ref>
===1900-present===
In the 20th and 21st centuries, Muslim astronomers have been making advances in moon sighting, while Muslim [[astronaut]]s and [[rocket scientist]]s have been involved in research on [[astronautics]] and [[space exploration]].
====Muslim participation in astronautics and space exploration====
[[Image:Kerimov21.jpg|thumb|[[Kerim Kerimov]], one of the founders of the [[Soviet space program]].]]
[[Kerim Kerimov]] from [[Azerbaijan]] (then part of the [[Soviet Union]]) was one of the most important key figures in early space exploration. He was one of the founders of the [[Soviet space program]], one of the lead architects behind the first [[human spaceflight]] ([[Vostok 1]]), and responsible for the launch of the first [[space station]]s (the [[Salyut]] and [[Mir]] series) as well as their predecessors (the [[Cosmos 186]] and [[Cosmos 188]]).<ref>{{citation|first=Peter|last=Bond
|url=http://findarticles.com/p/articles/mi_qn4158/is_20030407/ai_n12692130|contribution=Obituary: Lt-Gen Kerim Kerimov|title=[[The Independent]]|date=7 April 2003|accessdate=2008-01-22}}</ref><ref>{{citation|first=Betty|last=Blair|year=1995|title=Behind Soviet Aeronauts|journal=[[Azerbaijan International]]|volume=3|issue=3}}</ref>
[[Farouk El-Baz]] from [[Egypt]] worked for the rival [[NASA]] and was involved in the first [[Moon landing]]s with the [[Apollo program]], where he was secretary of the ''Landing Site Selection Committee'', ''Principal Investigator of Visual Observations and Photography'', chairman of the ''Astronaut Training Group'', and assisted in the planning of scientific explorations of the Moon, including the selection of landing sites for the Apollo missions and the training of astronauts in lunar observations and photography.<ref>{{cite web|url= http://www.islamonline.net/servlet/Satellite?c=Article_C&cid=1169545087624&pagename=Zone-English-HealthScience%2FHSELayout |title=Muslim Scientists and Space Exploration - Farouk El-Baz: With Apollo to the Moon - Interview|publisher=[[IslamOnline]]|accessdate=2008-01-15}}</ref>
In the late 20th and early 21st centuries, there have also been a number of Muslim astronauts, the first being [[Sultan bin Salman bin Abdulaziz Al Saud]] as a [[Payload Specialist]] aboard [[STS-51-G]] [[Space Shuttle Discovery]], followed by [[Muhammed Faris]] aboard [[Soyuz TM-2]] and [[Soyuz TM-3]] to [[Mir]] [[space station]]; [[Abdul Ahad Mohmand]] aboard [[Soyuz TM-5]] to Mir; [[Talgat Musabayev]] (one of the [[Spaceflight records#Total time in space|top 25 astronauts by time in space]]) as a [[flight engineer]] aboard [[Soyuz TM-19]] to Mir, commander of [[Soyuz TM-27]] to Mir, and commander of [[Soyuz TM-32]] and [[Soyuz TM-31]] to [[International Space Station]] (ISS); and [[Anousheh Ansari]], the first woman to travel to ISS and the fourth [[space tourist]].
In 2007, [[Sheikh Muszaphar Shukor]] from [[Malaysia]] travelled to ISS with his [[Expedition 16]] crew aboard [[Soyuz TMA-11]] as part of the [[Angkasawan program]] during [[Ramadan]], for which the [[National Fatwa Council]] wrote ''Guidelines for Performing Islamic Rites ([[Ibadah]]) at the International Space Station'', giving advice on issues such as [[Salah|prayer]] in a low-gravity environment, the location of [[Mecca]] from ISS, determination of prayer times, and issues surrounding [[Sawm|fasting]]. Shukor also celebrated [[Eid ul-Fitr]] aboard ISS. He was both an astronaut and an [[orthopedic surgeon]], and is most notable for being the first to perform [[biomedical research]] in space, mainly related to the characteristics and growth of liver [[cancer]] and [[leukemia]] cells and the crystallisation of various [[protein]]s and [[microbe]]s in space.<ref>{{Cite web|url=http://thestar.com.my/news/story.asp?file=/2007/10/11/nation/19136025&sec=nation|title=Mission in space|accessyear=2007|accessmonthday=October 13|publisher=[[The Star (Malaysia)|The Star]]|year=2007 |date=October 13, 2007|author=[[The Star (Malaysia)|The Star]]|language=English}}</ref>
Other prominent Muslim scientists involved in research on the [[space science]]s and space exploration include Essam Heggy who is working in the NASA Mars Exploration Program in the Lunar and Planetary Institute in Houston, as well as Ahmed Salem, Alaa Ibrahim, Mohamed Sultan, and Ahmed Noor.<ref>{{cite web|url=
http://www.islamonline.net/servlet/Satellite?c=Article_C&cid=1177155965285&pagename=Zone-English-HealthScience%2FHSELayout |title=Muslim Scientists and Space Exploration - Essam Heggy: Into the Heart of Mars - Interview|publisher=[[IslamOnline]]|accessdate=2008-01-15}}</ref>
====New efforts in moon sighting====
According to Islam, Muslims should observe religious duties during special days on the basis of the [[Islamic calendar|Islamic lunar calendar]]. Therefore, moon sighting is an important issue for Muslims.<ref name="Moon sighting">{{citation|url=http://online.wsj.com/article_email/SB119239099536758507-lMyQjAxMDE3OTEyNTMxOTUwWj.html |title=Muslim Moon Hunting Evolves|author=Farnaz Fassihi|date=October 15, 2007|journal=[[The Wall Street Journal]]|page=A8|accessdate=2008-01-24}}</ref> In recent years, due to global communication and using modern technologies to see the [[new moon]], a new trend has formed among Muslims in this field<ref>{{cite web|url=http://moonsighting.com|title=Moon Sighting|accessdate=2008-01-24}}</ref><ref>{{cite web|url=http://www.hilal-sighting.com|title=Hilal-Sighting]|publisher=[[Columbia University]], [[New York]]|accessdate=2008-01-24}}</ref><ref>{{cite web|url=http://www.icoproject.org|title=Islamic crescent's observation project|accessdate=2008-01-24}}</ref> and new [[Fiqh|religious]] questions have emerged.<ref>{{cite web|url=http://islam.about.com/od/ramadan/a/moonsighting.htm|title=Moon-Sighting at Ramadan|author=Huda|accessdate=2008-01-24}}</ref>
In 2005, [[Ayatollah]] [[Ali Khamenei]], [[Faqih|religious scholar]] and [[supreme leader]] of [[Iran]], issued a [[fatwa]] to use modern technologies for moon sighting. The [[Islamic Society of North America]] in Plainfield, Ind., followed suit last year. Muslims are scrambling for a technological edge in the annual moon-hunting ritual.<ref name="Moon sighting"/><ref>{{cite web|url= http://www.gulf-times.com/site/topics/article.asp?cu_no=2&item_no=109235&version=1&template_id=57&parent_id=56 |title=Fasting month of Ramadan begins in Qatar today|work=[[Gulf Times]]|date=23 September, 2006|accessdate=2008-01-24}}</ref>
Ayatollah Khamenei has established a Moon Observation Committee, comprised of [[cleric]]s who pore over sightings reported to centers. Scientists note the moon's angle, position, and illumination, and compare the sightings from the field with [[computer]]ized [[chart]]s that pinpoint where the moon should be. In Iran, groups of astronomers accompanied by a cleric are dispatched across the country, some using [[night vision]] gear lent by the [[military of Iran]] and [[high-definition]] telescopes from the [[List of universities in Iran|universities]]. Iran also sends up a chartered airplane with an astronomer aboard. The plane is loaded with sensitive observation and photographic equipment, along with a [[laptop]]. Iranian [[mapmaker]]s at the National Geography Organization in [[Tehran]] have created a three-dimensional map of the country identifying 70 locations where the new moon might best be seen.<ref name="Moon sighting"/> There are similar efforts in other [[Muslim countries]] as well.
There is also a competition among astronomers to see the younger moon with naked eyes. According to the Islamic lunar calendar in Iran, the new "World Record for Lunar Crescent Sighting" has been established on September 7, 2002 (Jamadi-al Thani 29, 1423 AH) by Mohsen Ghazi Mirsaeed on the north-west heights (2,110 meters ) of [[Zarand]] in Rashk Bala village (31°, 04' N , 56°, 28' E). The record for the moon age at the moment of first visibility with naked eyes is 11 hours and 42 minutes.<ref>{{cite web|url=http://www.icoproject.org/icop/grecord.html|title=A New World Record for Lunar Crescent Sighting By Mr. Mohsen G. Mirsaeed|publisher=Islamic Crescents' Observation Project|accessdate=2008-01-24}}</ref>
==Observatories==
The modern astronomical [[observatory]] as a [[research institute]]<ref name=Kennedy-1962/> (as opposed to a private [[observation post]] as was the case in ancient times)<ref name = "Micheau-992-3">{{citation|last=Micheau|first=Francoise|contribution=The Scientific Institutions in the Medieval Near East|pages=992-3}}, in {{Harv|Rashed|Morelon|1996|pp=985-1007}}</ref> was first introduced by medieval Muslim astronomers, who produced accurate [[Zij]] treatises using these observatories. The Islamic observatory was the first specialized astronomical institution with its own scientific [[staff]],<ref name=Kennedy-1962/> [[Director (education)|director]], astronomical [[Program Management|programme]],<ref name = "Micheau-992-3"/> large [[#Instruments|astronomical instruments]], and building where astronomical [[research]] and [[observation]]s are carried out. Islamic observatories were also the first to employ enormously large astronomical instruments in order to improve the accuracy of their observations.<ref name=Kennedy-1962>{{Harv|Kennedy|1962}}</ref>
The medieval Islamic observatories were also the earliest institutions to emphasize group research (as opposed to individual research) and where "theoretical investigations went hand in hand with observations." In this sense, they were similar to modern scientific research institutions.<ref>{{citation|last=Prof. Bakar|first=Osman ([[Georgetown University]])|publisher=CIC's annual Ottawa dinner|url=http://www.al-huda.com/Article_5%205.htm|title=Islam's Contribution to Human Civilization: Science and Culture|date=October 15, 2001|accessdate=2008-01-22}}</ref>
===Early observatories===
The first systematic observations in Islam are reported to have taken place under the patronage of [[al-Ma'mun]], and the first Islamic observatories were built in 9th century [[Iraq]] under his patronage.
In many private observatories from [[Damascus]] to [[Baghdad]], [[meridian (geography)|meridian]] degrees were measured, solar parameters were established, and detailed observations of the [[Sun]], [[Moon]], and [[planets]] were undertaken.
In the 10th century, the [[Buwayhid]] dynasty encouraged the undertaking of extensive works in Astronomy, such as the construction of a large scale instrument with which observations were made in the year 950. We know of this by recordings made in the ''zij'' of astronomers such as Ibn al-Alam. The great astronomer [[Abd Al-Rahman Al Sufi]] was patronised by prince [[Adud o-dowleh]], who systematically revised [[Ptolemy]]'s catalogue of [[star]]s. [[Sharaf al-Daula]] also established a similar observatory in [[Baghdad]]. And reports by [[Ibn Yunus]] and [[al-Zarqall]] in [[Toledo, Spain|Toledo]] and [[Córdoba, Spain|Cordoba]] indicate the use of sophisticated instruments for their time.
It was [[Malik Shah I]] who established the first large observatory, probably in [[Isfahan (city)|Isfahan]]. It was here where [[Omar Khayyám]] with many other collaborators constructed a [[zij]] and formulated the [[Iranian calendar|Persian solar calendar]], a.k.a. the ''jalali calendar'', the most accurate [[solar calendar]] to date. A modern version of this calendar is still in official use in [[Iran]] today.
[[Image:Maragheh Observatory.jpg|thumb|left|Current status of [[Maragheh observatory]].]]
===Late medieval observatories===
{{see|Maragheh observatory|Istanbul observatory of al-Din}}
The more influential observatories, however, were established beginning in the 13th century. The [[Maragheh observatory]] was founded by [[Nasīr al-Dīn al-Tūsī]] under the patronage of [[Hulegu Khan]] in the 13th century. Here, al-Tusi supervised its technical construction at [[Maragheh]]. The facility contained resting quarters for [[Hulagu Khan]], as well as a library and mosque. Some of the top astronomers of the day gathered there, and their collaboration resulted in important alternatives to the [[Ptolemaic model]] over a period of 50 years. The observations of al-Tusi and his team of researchers were compiled in the ''[[Zij-i Ilkhani]]''.
[[Image:Soviet Union stamp 1987 CPA 5876.jpg|thumb|[[Ulugh Beg]], founder of a large Islamic observatory in [[Samarkand]], honoured on this [[Soviet]] stamp.]]
In 1420, prince [[Ulugh Beg]], himself an astronomer and mathematician, founded another large observatory in [[Samarkand]], the remains of which were excavated in 1908 by Russian teams. In 1577, [[Taqi al-Din]] bin Ma'ruf founded the large [[Istanbul observatory of al-Din]], which was on the same scale as those in Maragha and Samarkand.
In the [[Mughal Empire]], [[Humayun]] built a personal observatory near [[Delhi]] in the 16th century, while [[Jahangir]] and [[Shah Jahan]] were also intending to build observatories but were unable to do so. After the decline of the Mughal Empire, the Hindu king [[Jai Singh II of Amber]] built several large observatories inspired by the famous Samarkand observatory. The instruments and observational techniques used at the observatory were mainly derived from the Islamic tradition, and the computational techniqes from the Hindu tradition.<ref name=Sharma/><ref name=Baber/>
===Modern observatories===
In modern times, many well-equipped observatories can be found in [[Jordan]],<ref>{{cite web|url=http://www.jas.org.jo/index2.html|title=Jordanian Astronomical Society|accessdate=2008-01-15}}</ref> [[Palestine]],<ref>{{cite web|url=http://www.pas.ps/maine.htm|title=Palestinian Astronomical Society|accessdate=2008-01-15}}</ref> [[Lebanon]],<ref>{{cite web|url=http://www.geocities.com/CapeCanaveral/Hall/6865|title=Lebanese Astronomical society|accessdate=2008-01-15}}</ref> [[UAE]],<ref>{{cite web|url=http://www.falak.ae|title=Emirates Astronomical Society|accessdate=2008-01-15}}</ref> [[Tunisia]],<ref>{{cite web|url=http://www.satunisia.info/angstro.htm|title=Société Astronomique de Tunise|accessdate=2008-01-15}}</ref> and other Arab states are also active as well. [[Iran]] has modern facilities at [[Shiraz University]] and [[Tabriz University]]. In December 2005, ''[[Physics Today]]'' reported of Iranian plans to construct a "world class" facility with a 2.0 metre [[telescope]] observatory in the near future.<ref>{{cite web|author=Feder Toni|date=July, 2004|url=http://www.physicstoday.org/vol-57/iss-7/p28a.html|title=Iran Invests in Astronomy|publisher=[[Physics Today]]|accessdate=2008-01-22}}</ref>
==Instruments==
{{see also|Inventions in the Muslim world}}
[[Image:Astrolabium.jpg|thumb|A [[Persia]]n ([[Iran]]ian) [[astrolabe]] from [[1208]].]]
Modern knowledge of the instruments used by Muslim astronomers primarily comes from two sources. First the remaining instruments in private and museum collections today, and second the treatises and manuscripts preserved from the Middle Ages.
Muslims made many improvements to instruments already in use before their time, such as adding new scales or details, and invented many of their own new instruments. Their contributions to astronomical instrumentation are abundant. Many of these instruments were often invented or designed for [[Islam]]ic purposes, such as the determination of the direction of [[Qibla]] or the times of [[Salah]].
===Astrolabes===
Brass [[astrolabe]]s were developed in much of the [[Islamic]] world, often as an aid to finding the [[qibla]]. The [http://www.soas.ac.uk/visitors/gallery/previous/islamicpatronage/popup25732.html earliest known example] is dated 315 (in the [[Islamic calendar]], corresponding to 927-8CE). The first person credited for building the Astrolabe in the Islamic world is reportedly [[Al-Fazari, Mohammad|Fazari]].<ref>[[Richard Nelson Frye]], ''Golden Age of Persia'', p. 163.</ref> Though the first primitive astrolabe to chart the stars was invented in the [[Hellenistic civilization]], al-Fazari made several improvements to the device. The Arabs then took it during the [[Abbasid]] [[Caliphate]] and perfected it to be used to find the beginning of [[Ramadan]], the hours of [[prayer]] ([[Salah]]), the direction of [[Mecca]] ([[Qibla]]), and over a thousand other uses.<ref name=Winterburn/>
In the 10th century, [[al-Sufi]] first described over 1000 different uses of an astrolabe, in areas as diverse as [[astronomy]], [[Islamic astrology|astrology, horoscope]]s, [[Mariner's astrolabe|navigation]], [[surveying]], [[time]]keeping, [[Qibla]], [[Salah]], etc.<ref name=Winterburn>{{cite web|author=Dr. Emily Winterburn ([[National Maritime Museum]])|url=http://www.muslimheritage.com/topics/default.cfm?ArticleID=529|title=Using an Astrolabe|publisher=Foundation for Science Technology and Civilisation|year=2005|accessdate=2008-01-22}}</ref>
;''Large astrolabe''
[[Ibn Yunus]] accurately observed more than 10,000 entries for the sun's position for many years using a large astrolabe with a diameter of nearly 1.4 metres.<ref name=Zaimeche/>
;''Mechanical geared astrolabe''
The first [[Mechanical engineering|mechanical]] astrolabes with [[gear]]s were invented in the Muslim world, and were perfected by Ibn Samh (c. 1020). One such device with eight [[gear]]-wheels was also constructed by [[Abū Rayhān al-Bīrūnī]] in 996. These can be considered as an ancestor of the [[mechanical clock]]s developed by later Muslim engineers.<ref>{{cite web|url=http://www.usc.edu/dept/MSA/introduction/woi_knowledge.html|title=Islam, Knowledge, and Science|publisher=[[University of Southern California]]|accessdate=2008-01-22}}</ref>
[[Image:Astrolabe-Persian-18C.jpg|thumb|left|An 18th century Persian [[astrolabe]], kept at The [[Whipple Museum of the History of Science]] in [[Cambridge]], England.]]
;''Navigational astrolabe''
The first [[Mariner's astrolabe|navigational astrolabe]] was invented in the Islamic world during the [[Middle Ages]], and employed the use of a [[Polar coordinate system|polar]] [[Map projection|projection]] system.<ref>Robert Hannah (1997). "''The Mapping of the Heavens'' by Peter Whitfield", ''Imago Mundi'' '''49''', pp. 161-162.</ref>
;''Orthographical astrolabe''
[[Abū Rayhān al-Bīrūnī|Abu Rayhan al-Biruni]] invented and wrote the earliest treatise on the [[Orthographic projection (cartography)|orthographical]] astrolabe in the [[1000s]].<ref name=Khwarizm/>
[[Image:Astrolabio andalusí Toledo 1067 (M.A.N.) 01.jpg|thumb|An [[astrolabe]] from [[al-Andalus]] dating back to 1067.]]
;''Saphaea and Zuraqi''
The first astrolabe instruments were used to read the rise of the time of rise of the [[Sun]] and fixed stars. In the 11th century, [[Arzachel]] (al-Zarqali) of [[al-Andalus]] constructed the first universal astrolabe which, unlike its predecessors, did not depend on the [[latitude]] of the observer, and could be used anywhere on the Earth. This universal astrolabe instrument became known in Europe as the "Saphaea". Another astrolabe, the Zuraqi is a unique astrolabe invented by [[al-Sijzi]] for a [[heliocentric]] planetary model in which the Earth is moving rather than the sky.<ref name=Nasr/>
;''Linear astrolabe''
A famous work by [[Sharaf al-Dīn al-Tūsī]] is one in which he describes the linear astrolabe, sometimes called the "staff of al-Tusi", which he invented.<ref>{{citation|url=http://www.britannica.com/eb/topic-342088/linear-astrolabe|contribution=Linear astrolabe|title=[[Encyclopædia Britannica]]|year=2007|accessdate=2008-01-22}}</ref>
;''Astrolabic clock''
[[Ibn al-Shatir]] invented the astrolabic [[clock]] in 14th century [[Syria]].<ref>{{Harv|King|1983|pp=545-546}}</ref>
===Analog computers===
Various [[analog computer]] devices were invented to compute the [[latitude]]s of the Sun, Moon, and planets, the [[ecliptic]] of the Sun, the time of day at which [[planetary conjunction]]s will occur and for performing [[linear interpolation]].
;''Equatorium''
The [[Equatorium]] was an [[analog computer]] invented by [[Abū Ishāq Ibrāhīm al-Zarqālī]] (Arzachel) in [[al-Andalus]], probably around 1015 CE. It is a mechanical device for finding the [[longitude]]s and positions of the [[Moon]], [[Sun]], and [[planet]]s, without calculation using a geometrical model to represent the [[celestial body]]'s mean and anomalistic position.<ref>{{Harv|Hassan}}</ref>
[[Image:planisphere.jpg|thumb|left|The [[planisphere]] was invented by [[Abū Rayhān al-Bīrūnī]].]]
;''Planisphere and mechanical geared calendar computer''
[[Abū Rayhān al-Bīrūnī]] invented and wrote the earliest treatise on the [[planisphere]], an [[analog computer]], in the [[1000s]].<ref name=Khwarizm/> He also invented the first [[Mechanical engineering|mechanical]] [[lunisolar calendar]] [[Analog computer|computer]] which employed a [[gear train]] and eight [[gear]]-wheels.<ref>{{Harv|Hill|1985}}</ref> This was an early example of a fixed-[[wire]]d knowledge processing [[machine]].<ref name=Oren>Tuncer Oren (2001). "Advances in Computer and Information Sciences: From Abacus to Holonic Agents", ''Turk J Elec Engin'' '''9''' (1): 63-70 [64].</ref>
[[Image:Torquetum.jpg|thumb|The [[torquetum]] was invented by [[Jabir ibn Aflah]] (Geber).]]
;''Torquetum''
[[Jabir ibn Aflah]] (Geber) (c. 1100-1150) invented the [[torquetum]], an observational instrument and mechanical analog computer device used to transform between [[spherical coordinate system]]s.<ref>{{citation|first=R. P.|last=Lorch|title=The Astronomical Instruments of Jabir ibn Aflah and the Torquetum|journal=[[Centaurus (journal)|Centaurus]]|volume=20|issue=1|year=1976|pages=11-34}}</ref> It was designed to take and convert measurements made in three sets of coordinates: [[horizon]], [[equator]]ial, and [[ecliptic]].
;''Mechanical astrolabe with geared calendar computer''
In 1235, Abi Bakr of [[Isfahan]] invented a brass [[astrolabe]] with a [[gear]]ed [[calendar]] movement based on the design of [[Abū Rayhān al-Bīrūnī]]'s mechanical calendar computer.<ref>Silvio A. Bedini, Francis R. Maddison (1966). "Mechanical Universe: The Astrarium of Giovanni de' Dondi", ''Transactions of the American Philosophical Society'' '''56''' (5): 1-69.</ref> Abi Bakr's geared astrolabe uses a set of [[gear]]-wheels and is the oldest surviving complete mechanical geared [[machine]] in existence.<ref>{{cite web|url=http://www.mhs.ox.ac.uk/astrolabe/exhibition/gearing.htm|title=Astrolabe gearing|publisher=[[Museum of the History of Science, Oxford]]|year=2005|accessdate=2008-01-22}}</ref><ref>{{cite web|url=http://www.mhs.ox.ac.uk/students/03to04/Astrolabes/Starholder_history.html|title=History of the Astrolabe|publisher=[[Museum of the History of Science, Oxford]]}}</ref>
;''Plate of Conjunctions''
In the 15th century, [[al-Kashi]] invented the Plate of Conjunctions, a computing instrument used to determine the time of day at which [[planetary conjunction]]s will occur,<ref>{{Harv|Kennedy|1947|p=56}}</ref> and for performing [[linear interpolation]].<ref name=Kennedy/>
;''Planetary computer''
In the 15th century, [[al-Kashi]] also invented a mechanical planetary computer which he called the Plate of Zones, which could graphically solve a number of planetary problems, including the prediction of the true positions in [[longitude]] of the [[Sun]] and [[Moon]],<ref name=Kennedy>{{Harv|Kennedy|1950}}</ref> and the [[planet]]s in terms of [[elliptical orbit]]s;<ref>{{Harv|Kennedy|1952}}</ref> the [[latitude]]s of the Sun, Moon, and planets; and the [[ecliptic]] of the Sun. The instrument also incorporated an [[alhidade]] and [[ruler]].<ref>{{Harv|Kennedy|1951}}</ref>
===Astronomical clocks===
The Muslims constructed a variety of highly accurate [[astronomical clock]]s for use in their observatories.<ref>{{Harv|Ajram|1992}}</ref>
;''Water-powered astronomical clocks''
[[Al-Jazari]] invented monumental [[Water clock|water-powered]] [[astronomical clock]]s which displayed moving models of the [[Sun]], [[Moon]], and [[star]]s. His largest astronomical clock displayed the [[zodiac]] and the [[Heliocentric orbit|solar]] and [[lunar orbit]]s. Another innovative feature of the clock was a [[pointer]] which traveled across the top of a [[gate]]way and caused automatic [[door]]s to open every [[hour]].<ref>{{Harv|Hill|1991}}</ref>
;''Mechanical observational clock''
Taqi al-Din invented the "observational clock", which he described as "a [[mechanical clock]] with three [[dial]]s which show the [[hour]]s, the [[minute]]s, and the [[second]]s." He used this for [[Astronomical clock|astronomical purposes]], specifically for measuring the [[right ascension]] of the [[star]]s. This is considered one of the most important innovations in 16th century practical astronomy, as previous [[clock]]s were not accurate enough to be used for astronomical purposes.<ref name=Tekeli/>
===Dials===
Muslim astronomers and engineers invented a variety of [[dial]]s for [[timekeeping]], and for determining the times of the [[Salat|five daily prayers]].
[[Image:SevillaGlorietaDelReloj01.JPG|thumb|left|A [[sundial]] in [[Seville]], [[Andalusia]], Spain.]]
;''Sundials''
Muslims made several important improvements to the theory and construction of [[sundial]]s, which they inherited from their [[Indian astronomy|Indian]] and [[Hellenistic civilization|Hellenistic]] predecessors. [[Al-Khwarizmi]] made tables for these instruments which considerably shortened the time needed to make specific calculations. Muslim sundials could also be observed from anywhere on the Earth. Sundials were frequently placed on mosques to determine the [[Salah|time of prayer]]. One of the most striking examples was built in the 14th century by the ''muwaqqit'' (timekeeper) of the [[Umayyad Mosque]] in [[Damascus]], [[Ibn al-Shatir]].<ref>{{Harv|King|1999a|pp=168-9}}</ref> Muslim astronomers and engineers were the first to write instructions on the construction of horizantal sundials, vertical sundials, and polar sundials.<ref name=King-Astronomy>{{citation|first=David A.|last=King|contribution=Astronomy and Islamic society|pages=163-8}}, in {{Harv|Rashed|Morelon|1996|pp=128-184}}</ref>
;''Navicula de Venetiis''
This was a universal horary [[dial]] invented in 9th century [[Baghdad]]. It was used for accurate timekeeping by the Sun and Stars, and could be observed from any [[latitude]].<ref>{{Harv|King|2005}}</ref> This was later known in Europe as the "Navicula de Venetiis",<ref>{{Harv|King|2003}}</ref> which was considered the most sophisticated timekeeping instrument of the [[Renaissance]].<ref name=King/>
;''Compass dial''
In the 13th century, [[Ibn al-Shatir]] invented the [[compass dial]], a [[time]]keeping device incorporating both a universal [[sundial]] and a magnetic [[compass]]. He invented for the purpose of finding the times of [[Salah]].<ref>{{Harv|King|1983|pp=547-548}}</ref>
[[Image:Armillary sphere.png|thumb|left|An [[armillary sphere]].]]
===Globes===
;''Armillary sphere''
An [[armillary sphere]] had similar applications to a [[celestial globe]]. No early Islamic armillary spheres survive, but several treatises on “the instrument with the rings” were written.
[[Image:Spherical astrolabe.jpg|thumb|The [[spherical astrolabe]] was invented by Islamic astronomers.]]
;''Spherical astrolabe''
The [[spherical astrolabe]] was first produced in the [[Islamic Golden Age|Islamic world]].<ref>Emilie Savage-Smith (1993). "Book Reviews", ''Journal of Islamic Studies'' '''4''' (2): 296-299.
{{quote|"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> It was an Islamic variation of the astrolabe and the armillary sphere, of which only one complete instrument, from the 14th century, has survived.
;''Celestial globes''
[[Celestial globe]]s were used primarily for solving problems in celestial astronomy. Today, 126 such instruments remain worldwide, the oldest from the 11th century. The altitude of the sun, or the [[Right Ascension]] and [[Declination]] of stars could be calculated with these by inputting the location of the observer on the [[meridian]] ring of the [[globe]].
In the 12th century, [[Jabir ibn Aflah]] (Geber) was "the first to design a portable celestial sphere to measure and explain the movements of celestial objects."<ref>{{cite web|title=An overview of Muslim Astronomers|url=http://www.muslimheritage.com/topics/default.cfm?ArticleID=232|publisher=FSTC Limited|date=26 December, 2001|accessdate=2008-02-01}}</ref>
;''Seamless celestial globe''
The [[Seamlessness|seamless]] [[celestial globe]] invented by Muslim metallurgists and instrument-makers in [[Mughal India]], specifically [[Lahore]] and [[Kashmir]], is considered to be one of the most remarkable feats in [[metallurgy]] and [[engineering]]. All [[globe]]s before and after this were seamed, and in the 20th century, it was believed by metallurgists to be technically impossible to create a metal globe without any [[wiktionary:seam|seams]]. It was in the 1980s, however, that Emilie Savage-Smith discovered several celestial globes without any seams in Lahore and Kashmir. The earliest was invented in Kashmir by the Muslim metallurgist Ali Kashmiri ibn Luqman in 998 AH (1589-90 CE) during [[Akbar the Great]]'s reign; another was produced in 1070 AH (1659-60 CE) by Muhammad Salih Tahtawi with Arabic and Sanskrit inscriptions; and the last was produced in Lahore by a Hindu metallurgist Lala Balhumal Lahuri in 1842 during [[Jagatjit Singh Bahadur]]'s reign. 21 such globes were produced, and these remain the only examples of seamless metal globes. These Mughal metallurgists developed the method of [[lost-wax casting]] in order to produce these globes.<ref>{{citation|first=Emilie|last=Savage-Smith|title=Islamicate Celestial Globes: Their History, Construction, and Use|publisher=Smithsonian Institution Press, Washington, D.C.|year=1985}}</ref><ref name=Kazi/>
These seamless celestial globes are considered to be an unsurpassed feat in metallurgy, hence some consider this achievement to be comparable to that of the [[Great Pyramid of Giza]] which was considered an unsurpassed feat in [[architecture]] until the 19th century.<ref name=Kazi>{{cite web|first=Najma|last=Kazi|title=Seeking Seamless Scientific Wonders: Review of Emilie Savage-Smith's Work|url=http://www.muslimheritage.com/topics/default.cfm?articleID=832|publisher=FSTC Limited|date=24 November, 2007|accessdate=2008-02-01}}</ref>
===Mural instruments===
A number of [[mural instrument]]s (including several different [[Quadrant (instrument)|quadrants]] and [[Sextant (astronomical)|sextant]]s) were invented by Muslim astronomers and engineers.
[[Image:Tycho instrument augsburg quadrant 20.jpg|thumb|The [[Quadrant (instrument)|quadrant]] was invented by [[Muhammad ibn Mūsā al-Khwārizmī]]. This illustration was drawn by [[Tycho Brahe]].]]
;''Sine quadrant''
The sine quadrant, invented by [[Muhammad ibn Mūsā al-Khwārizmī]] in 9th century [[Baghdad]], was used for astronomical calculations.<ref name=King-2002/>
;''Horary quadrant''
The first horary [[Quadrant (instrument)|quadrant]] for specific [[latitude]]s, was invented by [[Muhammad ibn Mūsā al-Khwārizmī]] in 9th century Baghdad, center of the development of quadrants.<ref name=King-2002/> It was used to determine time (especially the times of prayer) by observations of the Sun or stars.<ref>{{Harv|King|1999a|pp=167-8}}</ref>
;''Quadrans Novus''
Quadrans Vetus was a universal horary [[Quadrant (instrument)|quadrant]], an ingeniuous mathematical device invented by [[al-Khwarizmi]] in 9th century [[Baghdad]] and later known as the "Quadrans Vetus" (Old Quadrant) in medieval Europe from the 13th century. It could be used for any [[latitude]] on Earth and at any time of the year to determine the time in hours from the [[altitude]] of the Sun. This was the second most widely used astronomical instrument during the [[Middle Ages]] after the [[astrolabe]]. One of its main purposes in the Islamic world was to determine the times of [[Salah]].<ref name=King-2002>{{Harv|King|2002|pp=237-238}}</ref>
;''Quadrans Vetus''
The [[astrolabe|astrolabic]] [[Quadrant (instrument)|quadrant]] was invented in [[Egypt]] in the [[11th century]] or [[12th century]], and later known in Europe as the "Quadrans Vetus" (New Quadrant).<ref>{{Harv|King|Cleempoel|Moreno|2002|p=333}}</ref>
[[Image:Ulugh Beg observatory.JPG|thumb|left|[[Ulugh Beg]]'s [[mural instrument|mural]] [[Sextant (astronomical)|sextant]], constructed in [[Samarkand]], [[Uzbekistan]], during the 15th century.]]
;''Almucantar quadrant''
The first [[almucantar]] [[Quadrant (instrument)|quadrant]] was invented in the medieval Islamic world, and it employed the use of [[trigonometry]]. The term "almucantar" is itself derived from Arabic.<ref>Elly Dekker (1995), "An unrecorded medieval astrolabe quadrant from c. 1300", ''Annals of Science'' '''52''' (1): 1-47 [6].</ref> The Almucantar quadrant was originally modified from the [[astrolabe]].<ref name=King-Astronomy/>
;''Sextant''
The first [[Sextant (astronomical)|sextant]] was constructed in [[Ray, Iran]], by [[Abu-Mahmud al-Khujandi]] in [[994]]. It was a very large sextant that achieved a high level of accuracy for [[astronomy|astronomical]] measurements, which he described his in his treatise, ''On the obliquity of the ecliptic and the latitudes of the cities''.<ref>{{MacTutor|id=Al-Khujandi|title=Al-Khujandi}}</ref> In the 15th century, [[Ulugh Beg]] constructed the "Fakhri Sextant", which had a radius of approximately 36 meters. Constructed in [[Samarkand]], [[Uzbekistan]], the arc was finely constructed with a staircase on either side to provide access for the assistants who performed the measurements.
===Observation tube===
The first reference to an "observation tube" is found in the work of [[al-Battani]] (Albatenius) (853-929), and the first exact description of the observation tube was given by [[al-Biruni]] (973-1048), in a section of his work that is "dedicated to verifying the presence of the new cresent on the horizon." Though these early observation tubes did not have [[Lens (optics)|lenses]], they "enabled an observer to focus on a part of the sky by eliminating [[light]] inteference." These observation tubes were later adopted in [[Latin]]-speaking Europe, where they influenced the development of the [[telescope]].<ref>Regis Morelon, "General Survey of Arabic Astronomy", pp. 9-10, in {{Harv|Rashed|Morelon|1996|pp=1-19}}</ref>
===Other instruments===
Various other astrononmical instruments were also invented in the Islamic world:
*The first astronomical uses of the magnetic [[compass]] is found in a treatise on astronomical instruments written by the [[Yemen]]i [[sultan]] al-[[Ashraf]] (d. 1296). This was the first reference to the compass in astronomical literature.<ref>Emilie Savage-Smith (1988), "Gleanings from an Arabist's Workshop: Current Trends in the Study of Medieval Islamic Science and Medicine", ''[[Isis (journal)|Isis]]'' '''79''' (2): 246-266 [263].</ref>
[[Image:Alidade for ceiling projector.JPG|right|thumb|An [[alidade]].]]
*The [[Alhidade]] was invented in the Islamic world, while the term "alhidade" is itself derived from Arabic.
*A [[compendium]] was a multi-purpose astronomical instrument, first constructed by the Muslim astronomer [[Ibn al-Shatir]] in the 13th century. His compendium featured an [[alhidade]] and polar [[sundial]] among other things. Al-Wafa'i developed another compendium in the 15th century which he called the "equatorial circle", which also featured a horizontal sundial. These compendia later became popular in [[Renaissance]] Europe.<ref name=King-Astronomy/>
*Islamic [[Quadrant (instrument)|quadrants]] used for various astronomical and timekeeping purposes from the 10th century introduced [[orthogonal]] and [[regular grid]]s and markings that are identical to modern [[graph paper]].<ref>Josef W. Meri (2006), ''Medieval Islamic Civilization: An Encyclopedia'', p. 75, [[Taylor and Francis]], ISBN 0415966914.</ref><ref>{{Harv|King|1999b|p=17}}</ref>
*In 17th century [[Safavid dynasty|Safavid Persia]], two unique [[brass]] instruments with [[Mecca]]-centred [[world map]]s engraved on them were produced primarily for the purpose of finding the [[Qibla]]. These instruments were engraved with [[Cartography|cartographic]] [[Grid reference|grids]] to make it more convenient to find the direction and distance to Mecca at the centre from anywhere on the Earth, which may be based on cartographic grids dating back to 10th century [[Baghdad]].<ref name=King>{{Harv|King|2004}}</ref> One of the two instruments, produced by Muhammad Husayn,<ref>{{Harv|Iqbal|2003}}</ref> also had a [[sundial]] and [[compass]] attached to it.<ref>{{Harv|King|1997|p=62}}</ref>
*The shadow square was an instrument used to determine the linear height of an object, in conjunction with the [[alidade]], for angular observations.<ref>{{cite web|url=http://www.nmm.ac.uk/collections/search/lightbox.cfm/category/90286|title=Shadow square|publisher=[[National Maritime Museum]]|accessdate=2008-01-22}}</ref> It was invented by [[Muhammad ibn Mūsā al-Khwārizmī]] in 9th century Baghdad.<ref>{{Harv|King|2002|pp=238-239}}</ref>
==List of notable treatises==
===Zij treatises===
{{main|Zij}}
*[[Ibrahim al-Fazari]] (d. 777) and [[Muhammad al-Fazari]] (d. 796/806)
**''Az-Zij ‛alā Sinī al-‛Arab'' (c. 750)
*[[Yaqūb ibn Tāriq]] (d. 796)
**''Az-Zij al-Mahlul min as-Sindhind li-Darajat Daraja''
*[[Muhammad ibn Mūsā al-Khwārizmī]] ([[Latin]]ized as ''Algorismi'') (c. 780-850)
**''Zij al-Sindhind'' (c. 830)
*[[Muhammad ibn Jābir al-Harrānī al-Battānī]] (Latinized as ''Albategni'') (853-929)
**''Az-Zij as-Sabi''
*[[Abd Al-Rahman Al Sufi]] (Latinized as ''Azophi'') (903-986)
**''[[Book of Fixed Stars]]'' (c. 964)
*[[Al-Zarqali]] (Latinized as ''Arzachel'') (1028-1087)
**''[[Tables of Toledo]]''
*[[Al-Khazini]] (fl. 1115-1130)
**''Az-Zij as-Sanjarī'' (''Sinjaric Tables'') (1115-1116)
*[[Nasīr al-Dīn al-Tūsī]] (1201-1274)
**''[[Zij-i Ilkhani]]'' (''Ilkhanic Tables'') (1272)
*[[Jamshīd al-Kāshī]] (1380-1429)
**''Khaqani Zij''
*[[Ulugh Beg]] (1394-1449)
**''[[Zij-i-Sultani]]'' (1437)
*[[Taqi al-Din]] (1526-1585)
**''Unbored Pearl'' (1577-1580)
===Almanacs===
The word "[[Almanac]]" is an [[Arabic language|Arabic]] word.<ref>{{Harv|Glick|Livesey|Wallis|2005|p=29}}</ref> The modern almanac differs from earlier astronomical tables (such as the earlier [[Babylonian astronomy|Babylonian]], Ptolemaic and [[Zij]] tables) in the sense that "the entries found in the almanacs give directly the positions of the celestial bodies and need no further computation", in contrast to the more common "auxiliary astronomical tables" based on Ptolemy's ''Almagest''. The earliest known almanac in this modern sense is the ''Almanac of Azarqueil'' written in 1088 by [[Abū Ishāq Ibrāhīm al-Zarqālī]] (Latinized as Azarqueil) in [[Toledo, Spain|Toledo]], [[al-Andalus]]. The work provided the true daily positions of the sun, moon and planets for four years from 1088 to 1092, as well as many other related tables. A [[Latin]] translation and adaptation of the work appeared as the ''[[Tables of Toledo]]'' in the 12th century and the ''[[Alfonsine tables]]'' in the 13th century.<ref>{{Harv|Glick|Livesey|Wallis|2005|p=30}}</ref>
===Treatises on instruments===
In the 12th century, [[al-Khazini]] wrote the ''Risala fi'l-alat'' (''Treatise on Instruments'') which had seven parts describing different scientific [[instrument]]s: the [[Triquetrum (astronomy)|triquetrum]], [[dioptra]], a [[triangle|triangular]] instrument he invented, the [[Quadrant (instrument)|quadrant]] and [[Sextant (astronomical)|sextant]], the [[astrolabe]], and original instruments involving [[reflection]].<ref>Robert E. Hall (1973). "Al-Biruni", ''Dictionary of Scientific Biography'', Vol. VII, p. 338.</ref>
In 14th century [[Egypt]], Najm al-Din al-Misri (c. 1325) wrote a treatise describing over 100 different types of scientific and astronomical instruments, many of which he invented himself.<ref name=King/>
In 1416, [[al-Kashi]] wrote the ''Treatise on Astronomical Observational Instruments'', which described a variety of different instruments, including the [[Triquetrum (astronomy)|triquetrum]] and [[armillary sphere]], the [[Equinox|equinoctial]] armillary and [[Solstice|solsticial]] armillary of [[Mo'ayyeduddin Urdi]], the [[sine]] and [[versine]] instrument of Urdi, the [[Sextant (astronomical)|sextant]] of [[al-Khujandi]], the Fakhri sextant at the [[Samarqand]] observatory, a double quadrant [[Azimuth]]-[[altitude]] instrument he invented, and a small armillary sphere incorporating an [[alhidade]] which he invented.<ref>{{Harv|Kennedy|1961|pp=104-107}}</ref>
===Other works===
*[[Ja'far Muhammad ibn Mūsā ibn Shākir]] (Latinized as ''Mohammed Ben Musa'') (800-873)
**''Book on the motion of the orbs''
**''Astral Motion''
**''The Force of Attraction''
*[[Ahmad ibn Muhammad ibn Kathīr al-Farghānī]] (Latinized as ''Alfraganus'') (d. 850)
**''Elements of astronomy on the celestial motions'' (c. 833)
**''Kitab fi Jawami Ilm al-Nujum''
*[[Ibn al-Haytham]] (Latinized as ''Alhacen'') (965-1039)
**''On the Configuration of the World''
**''Doubts concerning Ptolemy'' (c. 1028)
**''The Resolution of Doubts'' (c. 1029)
**''The Model of the Motions of Each of the Seven Planets'' (1029-1039)
*[[Abū Rayhān al-Bīrūnī]] (973-1048)
**''Kitab al-Qanun al-Mas'udi'' (Latinized as ''Canon Mas’udicus'') (1031)
*[[Juzjani, Abu Ubaid|Abu Ubayd al-Juzjani]] (c. 1070)
**''Tarik al-Aflak'' (1070)
*''Al-Istidrak ala Batlamyus'' (''Recapitulation regarding Ptolemy'') (11th century)
*[[Al-Khazini]] (fl. 1115-1130)
**''Risala fi'l-alat'' (''Treatise on Instruments'')
*[[Nasīr al-Dīn al-Tūsī]] (1201-1274)
**''Al-Tadhkirah fi'ilm al-hay'ah'' (''Memento in astronomy'')
*'Umar al-Katibi al-[[Qazwini]] (d. 1277)
**''Hikmat al-'Ain''
*[[Qutb al-Din al-Shirazi]] (1236-1311)
**''The Limit of Accomplishment concerning Knowledge of the Heavens''
*[[Ibn al-Shatir]] (1304–1375)
**''A Final Inquiry Concerning the Rectification of Planetary Theory''
*[[Ali Kuşçu|Ali al-Qushji]] (d. 1474)
**''Concerning the Supposed Dependence of Astronomy upon Philosophy''
*Shams al-Din al-Khafri (d. 1525)
**''The complement to the explanation of the memento''
==Arabic star names==
{{main|List of Arabic star names}}
Many of the modern names for numerous [[star]]s and [[constellation]]s are derived from their [[Arabic language]] names. Examples include: [[Acamar]], [[Aldebaran]], [[Altair]], [[Baham]], [[Baten Kaitos]], [[Caph]], [[Dabih]], [[Edasich]], [[Furud]], [[Gienah]], [[Hadar]], [[Izar]], [[Jabbah]], [[Keid]], [[Lesath]], [[Mirak]], [[Nashira]], [[Okda]], [[Phad]], [[Rigel]], [[Sadr]], [[Tarf]], and [[Vega]], as well as a number of other stars. Some of these names originated in the pre-Islamic [[Arabian Peninsula]], but many came later, as translations of [[Ancient Greek]] descriptions.<ref>{{cite web|url=http://astro.isi.edu/reference/starnames.txt|title=Arabic Star names}}</ref>
==See also==
*[[Arab and Persian astrology]]
*[[History of astronomy]]
*[[Hebrew astronomy]]
*[[Inventions in the Muslim world]]
*[[Islamic astrology]]
*[[Islamic Golden Age]]
*[[Islamic science]]
*[[List of Arab scientists and scholars]]
*[[List of Iranian scientists and scholars]]
*[[List of Muslim astronomers]]
*[[List of Muslim scientists]]
*[[Zij]]
==Notes==
{{reflist|2}}
==References==
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</div>
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== കൂടുതല് അറിവിന് ==
| 