The perfection targeted in the religious, official (administrative) and the social spheres of the Islamic civilization relies on the precision in calculation and on the devices that provide it. This fact indicates that the religious and social legitimacy, in a way, depends on the mathematical sciences, especially astronomy. In this sense, many arrangements had to be undertaken in the Ottoman Empire such as the development of astronomical, geometric-trigonometric tables and techniques, the improvement of the present tools and exact calculations in order to be able to regulate many issues according to the capital of the state such as the settlement of the worship hours, the appointment of the geometric-trigonometric direction of the Kabah located in Mecca, the determination of the beginnings and the ends of months, days and years that carry religious and political significance such as the Ramadan. On the other hand, some issues such as the travel of ships, the measurement of distance, the detection of route and even astrology were to an extent dependent on mathematics and astronomical devices like the astrolabe and the trigonometric quantrant (rub-i mujayyab).
Within this framework, the astronomical tradition in the Ottoman Empire, as a natural continuation of the Islamic civilization, was a product of an environment shaped by the representatives of the Maragha School of mathematics-astronomy during the Seljuki and particularly the Ilkhanid eras. It can be claimed that many astronomers contributed to this formation including Kutbuddin Shirazi (d. 1311), who instructed for a long time at the medreses of Sivas and Kayseri as one of the most prominent theoretical astronomers of the history of astronomy and his students. In fact, the affiliation of Ibn Sertak (d. 1328 c.), who was the mentor of Davud Kayseri, (d. 1350), the head instructor of the first Ottoman medrese established in Iznik, with the Maragha school is the greatest indication of this continuation.
Despite the fact that theoretical astronomy was taught in medreses during the establishment period of the Ottoman Empire and the fact that many topics related to astronomy were discussed in the works of theology and philosophy, most of these works dealt with the calendar and practical astronomy in parallel to the needs of the society as seen in the example of Ahmed-i Dai (d. 1421). However, the observations of Abdulvacid b. Muhammed (d. 1435) in Kütahya signify the presence of astronomical research oriented towards observation even though it was at a small scale. The presence of commentaries on some astronomical tables, the compilation of works on astronomical devices such as the astrolabe and the trigonometric quantrant are also worth noting in terms of their indication of the practical character of astronomy in this period.
Musa Kadı-zade (d. 1444), as the head instructor of Ulug Bey's medrese in Samarkand and the director of the observatory at one point, lived outside the borders of the Ottoman Empire. However, being raised in the Ottoman capital of the period, Bursa, he was also a student of Mehmed Fenari (d. 1431), who had organized the Ottoman scientific (ilmiye) institution. Kadı-zade defined the tradition of Ottoman theoretical astronomy through the works he wrote on theoretical astronomy and the students that he trained. One of his exceptional students, Fethullah Şirvani (d. 1486) first wrote commentaries on the works of his mentor and then penned some additional commentary on the important theoretical work of Nasiruddin Tusi (d. 1273) on astronomical history, el-Tezkire fi ilm el-hey'e. However, both the theoretical and planetary astronomy and the practical astronomy of the Ottoman Empire were actually established by the student of both Kadı-zade and Ulug Bey (d. 1449), Ali Kuşçu (d. 1474) of the Samarkand school as well as his friends and students. While the theoretical and planetary astronomy was to a great extent dependent on the accumulation of the schools of Maragha and Samarkand, practical astronomy and timekeeping were connected to the classical Islamic tradition of timekeeping that reached its peak in Damascus in the hands of Şemseddin Halili (d. 1397?) and Ibn Shatir (d. 1375) in the fourteenth century. Trying to cleanse the Hermetic-Phytagorean mysticism out of the mathematical sciences, the Aristotelian physical and metaphysical principles out of astronomy and optics, Ali Kuşçu proposed a new kinematic-geometrical model regarding the movements of the planet Mercury. Moreover, he developed an eccentric model for both the inner and the outer planets in the place of epicyclical models which proved to be crucial for the heliocentric cosmology-astronomy on its way to Copernicus (d. 1543) over Regiomontanus (d. 1476). These theoretical works of Ali Kuşçu were later extended by Ahaveyn (d. 1499) and his grandson, Mirim Çelebi (d. 1524), but criticized by Abdulali Bircendi (d. 1528). They were further transformed into a radical proposal by Ibn Nakib (d. 1563) on the basis of Ibn Shatir's new astronomy. The Ottoman astronomers continued to tackle these theoretical problems that found its roots in the Maragha mathematical-astronomical school until the eighteenth century.
Apart from the almanac(devr-i daim) calendar of Sheikh Vefa (d. 1491) that was applied for many years in the field of practical astronomy, Mehmed Konevi (d. 1523) operated with the consideration of the astronomical needs of his era, the classical period of the Ottoman Empire. Reordering the Hellenistic and Islamic astronomical heritage according to Istanbul, Mehmed Konevi led the way to the transmission of the abovementioned heritage in especially the field of practical astronomy from Arabic and Persian into Turkish through the works he penned in Turkish. In this fashion, he both set an example for the following astronomers and prepared the ground for the turkification of the astronomical terminology. The Ottoman traditions of timekeeping, practical astronomy and mathematical geography were reproduced in Turkish by taking Istanbul as the center in real sense by his follower Mustafa el-Muvakkit (d. 1571). This process resulted in the compilation of the first Turkish theoretical astronomical text by Seydi Ali Reis (d. 1563). Moreover, the naval astronomy and geography were developed by taking into account the works of the great captains Ibn Macit and Suleyman el-Mehri.
The theoretical and practical astronomy of the Ottoman Empire that derived from the classical Islamic heritage reached its peak at the time of Takiyuddin Rasid (d. 1585), the mathematician, physicist and mechanical scientist who united the schools of Maragha, Samarkand and Cairo-Damascus in himself and established the Istanbul Observatory. Takiyuddin improved the old observational devices and invented many new tools; he used the mechanical-automatic watch for the first time in observational activity. Through his astronomical tables, for the first time in history ever since the Babylonians, he abandoned the sexagesimal system and applied decimal fractions to both astronomy and trigonometry. He prepared the sinus and tangent tables according to this calculation. The mathematical precision comprising his foremost aim, Takiyuddin corrected the deficiencies of the Samarkand school through his studies. Compared to his counterparts in Europe such as Copernicus and Tycho Brahe (d. 1601), his works appear to have surpassed their level in terms of some devices, precision in calculation and some new diagnoses.
In the Ottoman Empire, the astronomical works based on observation are not limited to the Istanbul Observatory constructed by Takiyuddin. While the sources have recorded that solar observations were carried out in Istanbul during the reign of Sultan Bayezid II, Abdulali Bircendi has explained in a work penned by him that he established an observatory of a small scale in Trabzon, where he performed his own observations.
Both the theoretical and the practical astronomical works following the sixteenth century operated within the frames of a classical paradigm identified as "normal science" by Kuhn. The Ottoman astronomers continued to produce theoretical and practical works on many subjects and also to write treatises on many astronomical devices until the beginning of the twentieth century. The emphasis was laid on the problems related to the cosmology of the astronomy of the period and the relationship between astronomy and religion. For example, the almanaca(ruzname) prepared by Mehmed Darendevi (d. 1739) was implemented not only in the Ottoman geography but also in Western Europe, as acknowledged by Albert Toderini.
Modern astronomy entered the Ottoman astronomical world through the translation of İbrahim Efendi in between 1660 and 1664. This process was sustained by the translations of Ebu Bekr Dımeşki (d. 1691). The information introduced by modern astronomy settled well into the society following the works of Ibrahim Muteferrika (d. 1745) and it did not create a conflict in Ottoman mentality as it did in Western Europe. On the contrary, the new ideas in astronomy were interpreted as a technical detail. In this course progressing with the translations of Osman b. Abdulmennan (d. 1786 c.), the Ottoman astronomers began to translate many astronomical tables of the western astronomers and the calendars of the Ottoman state were prepared accordingly. The instructors of the new schools of higher learning established in 1773 known as the mühendishane including Huseyin Rifki (d. 1817), Seyyid Ali Pasa (d. 1846) and especially Ishak Hoca (d. 1836) contributed to the adoption of this information. Ishak Hoca dedicated a large part of his work, Mecmua-ı ulum-ı riyaziye, which covered the most recent information in all fields of the period, to the details of astronomy; as such, the ancient astronomy was officially abandoned in favor of the modern astronomy.
The astronomical works that were continued by figures such as Ahmed Cevdet Paşa (d. 1900) , Ahmet Muhtar Paşa (d. 1918) and Salih Zeki (d. 1921) gained a new dimension with the appointment of Mehmet Fatin Gökmen (d. 1955) to the directorate of the Observatory (established in 1867); by supervising the construction of the Kandilli Observatory after the foundation of the Turkish Republic, he extended the Ottoman accumulation to the Republican era and as such, he provided for the continuity of astronomical research from the Ottomans to the Republic.
Demir, Remzi, Takiyüddin'de Matematik ve Astronomi, Ankara: 2000.
Fazlıoğlu, İhsan, "Osmanlı felsefe-biliminin arkaplanı: Semerkand matematik-astronomi okulu", Dîvân İlmî Araştırmalar Dergisi, İstanbul 2003/1, S. 14, s. 1-66.
Fazlıoğlu, İhsan, "The Samarqand Mathematical-Astronomical School: A Basis for Ottoman Philosophy and Science." Journal for the History of Arabic Science 14 (2008): 3-68.
Fazlıoğlu, İhsan, "Taqi al-Din", Biographical Encyclopaedia of Astronomers (edit. Thomas Hockey), c. II, Springer, New York 2007, s. 1122-1123.
Fazlıoğlu, İhsan, "Qushji", Biographical Encyclopaedia of Astronomers (edit. Thomas Hockey), c. II, Springer, New York 2007, s. 946-948.
Fazlıoğlu, İhsan, "Mirim Chalabî", Biographical Encyclopaedia of Astronomers (edit. Thomas Hockey), c. II, Springer, New York 200, s. 788-789.
Fazlıoğlu, İhsan, "Mustafa b. Ali al-Muwaqqıt", Biographical Encyclopaedia of Astronomers (edit. Thomas Hockey), c. I, Springer, New York 2007, s. 33-34.
Fazlıoğlu, İhsan, "Fath Allah al-Shirwanî"", Biographical Encyclopaedia of Astronomers (edit. Thomas Hockey), c. II, Springer, New York 2007, s. 1055-1056.
Fazlıoğlu, İhsan, "Katib Sinan al-Qonawî", Biographical Encyclopaedia of Astronomers (edit. Thomas Hockey), c. II, Springer, New York 2007, s. 945-946.
Fazlıoğlu, İhsan, ""Omar al-Darandawî"", Biographical Encyclopaedia of Astronomers (edit. Thomas Hockey), c. I, Springer, New York 2007, s. 277-278..
Mordmann, "Das Observatorium des Taqi ed-Din zu Pera", Der İslam, XIII, 1913, 82-96.
Ragep, F. Jamil, Ali Qushji and Regiomontanus: Eccentric Transformations and Copernican Revolutions, Journal History of Astronomy, xxxvi (2005), 359-371.
Saliba, George. "Al-Qushji's Reform of the Ptolemaic Model for Mercury." Arabic Sciences and Philosophy 3 (1993): 161-203.
Sayılı, Aydın Sayılı, The Observatory in Islam, Ankara: 1960, pp. 289-305.
Şeşen, Ramazan (ve diğerleri), Osmanlı Astronomi Literatürü Tarihi (OALT), (History of astronomy literature during the Ottoman period). Vol. I-II, Istanbul: IRCICA, 1997.
Tekeli, Sevim (edit.), Alat el-Rasadiyye li Zic-i Şehinşahiyye, İTED, III/1-2, 1960, pp. 1-30.
------------, "Nasiruddin, Takiyüddin ve Tycho Brahe'nin Rasad Aletlerinin Mukayesesi", Ankara Üniversitesi, Dil ve Tarih-Coğrafya Fakültesi Dergisi, vol. XVI/3-4, Ankara 1958, pp. 301-353.