Baghdad, the fairy city of the Arabian Nights and capital of the famous Harun-ar-Rashid, the greatest emperor of his time, had the distinction of being the foremost centre of art and culture during mediaeval times.  Renowned scholars and translators, artists and scientists flocked to this great metropolis from all parts of the world and adorned the learned assemblies of Harun and Mamun, who, besides being celebrated scholars themselves, were the greatest patrons of learning that the world has ever known.  The Darul Hukama (House of Wisdom) founded by Mamun-ar-Rashid in Baghdad housed some of the most eminent scholars of the world belonging to different castes and creeds.  The spade work done by the scholars of the House of Wisdom provided the foundation by which the stately edifice of Islamic learning was built.  The caliphate of Mamun, undoubtedly constitutes the most glorious epoch in saracenic history and has rightly been called the 'Augustan age of Islam'.  "The twenty years of his reign" says Ameer Ali, " have left enduring monuments of the intellectual development of the Muslim in all directions of thought.  Their achievements were not restricted to any particular branch of science or literature, but ranged over the whole course of the domain of intellect;   speculative philosophy and 'belles lettres' were cultivated with as much avidity as the exact sciences".' "We see for the first time" says Oelsner, "perhaps in the history of the world, a religious and despotic government allied to philosophy, preparing and partaking in its triumphs".l

Astronomy, in the real sense, started among the Arabs during the early period of the Abbasid Caliphate.  It was much influenced by Sidhanta, a work in Sanskrit brought from India to Baghdad and translated into Arabic by Ibn Ibrahim al-Fazari and later on by Abu Musa Khwarizmi.  Pahlavi tables (zij) compiled during the Sasanid period and Greek astronomical works translated during this period prepared the ground for Arabian astronomy.  Ptolemy's Al-magest went into several translations in Arabic--the best being the one by Hajjaj Ibn Mater (827-28) and another by Humayun Ibn Ishaq, revised by Thabit bin Qurra (d/901).

Khwarizmi has written a valuable treatise on astronomy and has compiled his own Tables (zij) which, after two centuries was revised by Spanish atronomer Majriti (011007) and was translated into Latin by Adelard of Bath.  This formed the basis of later astronomical pursuits both in the East and the West and replaced all earlier tables of Greek and Indian astronomers.  This table was also adopted in China.

Mashallah and Ahmad bin Muhammad alNahavandi were the earliest Arab astronomers who flourished during the reign of Mansur, the second Abbasid Caliph.  Mashallah was called the Phoenix of his age by Abul Faraj.  He is distinguished for writing several valuable treatises on 'Astrolabe' the armillary sphere and the movements of heavenly bodies which have been acclaimed by later scientists.  Ahmad compiled from his observations an astronomical table known as Al-Mustamal which registered an advance over earlier notions of the Greeks and Hindus.

It was during the reign of Mamun, that practical steps were taken for the advancement of astronomy and several observatories equipped with the latest instruments were set up at various places in his domain.  One of them was the observatory in Jundeshapur, in south-west Persia.  Early in the 9th century A.D. the first regular observations (Rasd) with the best available and fairly accurate instruments were made in this observatory.  Mamun got a degree of meridian measured in the plain of Sanjar and followed a method which was much superior to that of Greeks.  The astronomical observations made during the reign of Mamun regarding the equinoxes, the eclipses, the apparitions of the comets and' other celestial phenomena, have earned an important place in the astronomical annals of mediaeval times.  "The size of the earth was calculated", says Ameer Ali "from the measurement of a degree on the shores of the Red Sea--this at a time when Christian Europe was asserting the flatness of the earth".' Attached to his Darul Hukama (House of Wisdom), Mamun erected at Baghdad near the Shamsiyah gate, an astronomical observatory under the directorship of Sind Ibn All, a converted Jew and Yahya Ibn Abi Mansur (830 or 831 A.D.).  According to C.  A.  - Nallino, "Here astronomers made systematic observation of celestial movements and verified with remarkably precise results all the fundamental elements of the Almagest:  the obliquity of the ecliptic, the precession of the equinoxes, the length of the solar year, etc." With the aid of these observations the astronomical tables called the Tested Tables or Tables of Mamun were prepared.  According to Ibn al-Ibri, Mamun later established another observatory on Mt.  Qasiyum outside Damascus.  Afterwards several other observatories were erected at Wasit, Apamea, etc.  Musa bin Shakir was a well-known engineer during the reign of Harun-ar-Rashid.  His sons, specialised in astronomical researches and earned a great reputation as astronomers during the reign of Mamun and his two successors.  Their research regarding the movements of solar and other astral bodies, was remarkable.  They ascertained the size of the earth, the obliquity of the ecliptic, the variations of the lunar latitudes and the precession of the equinoxes!  The work of the sons of Musa bin Shakir was continued by Al-Naziri and Muhammad bin Isa Abu Abdulla, who made notable additions to it.  The invention of the telescope by Abul Hasan forms a landmark in the advancement of astronomical observations and, in improved form, was used with remarkable success in the observatories of Maragha, Cairo and Seville.  A number of Mamun's astronomers headed by Musa Khwarizmi and Musa Ibn Shakir successfully engaged in one ofthe most oblicate geodetic operations, i.e., the determination of the size and the circumference of the earth.  The measurement carried out in the plain of Sanjar and also at Palmyra, "yielded 56 2/3 Arabic miles as the length of a degree of the meridian--a remarkably accurate result, exceeding the real length of the degree at the place by about 2,877 feet" says C.  A.  Nallino.--"This would make the diameter of the earth 6,500 miles and its circumference 20,400 miles".' Muhammad Bin Musa al-Khwarizmi, a versatile genius of Islamic history translated the Sidhanta or Indian tables and wrote a commentary on it.  He has written a valuable treatise on astronomy and has compiled his own tables (zij) which after two centuries were revised by the Spanish astronomer Majriti and translated into Latin by Adelard of Bath in 1126 A.D.  These formed the basis of later astronomical works in the East and the West, replacing all earlier tables by Greek and Indian astronomers.  These tables were also used in China.

Ibrahim al-Fazari was the first Muslim to construct an astrolabe.  He wrote on the use of the armillary sphere and prepared tables in accordance with the Arabic years.  One of the earliest Arabic treatises on this instrument was written by Isa-al-Asturlabi who resided in Baghdad at about 830 A.D.

Abul Abbas al-Farghani (Alfraganus), a resident of Farghana in Central Asia, was an astronomer of repute, who in 861 A.D., according to Ibn Abi Usabiyah (Vol.  I, page 207), supervised for the Abbasid Caliph Al-Mutawakkil the erection of a Nilometer at Fustat.
His well-known work  AI-Mudkhil-ila-ilm-hayat-al-aflak (compendium of astronomy) was translated into Latin in 1135 A.  D.  by John of Seville and Gerard of Cremona.  It was also rendered into Hebrew.  "The introduction of Astronomy into Christian Europe", says J.  W.  Draper, "has been attributed to the translation of the works of Muhammad Fargani.  In Europe, also, the Arabs were the first to build observatories;   the Giralda, or Tower of Seville was erected under the superintendence of Geber, the mathematician"

The Buwayhid Sultans were also great patrons of learning and were surrounded by a galaxy of talented scholars invited from the four corners of the Islamic world.  The Buwayhid Sultan Sharaf al-Daulah (982--89, A.D.) founded a good observatory in his palace at Baghdad where such celebrated astronomers as Abdur Rahman al-Sufi, Ahmad al-Saghani and Abul Wafa carried on their research.  Abdur Rahman al-Sufi wrote al-kawakib al-Sabitah (fixed stars) which is known as a masterpiece of observational astronomy.  Alkohi, another astronomer attached to the same dynasty, studied the movements of the planets and his research regarding the summer solstice and the autumnal equinox were of considerable value.  Abul Wafa, born in 939 A.  D.  in Khorasan and established in Iraq was an outstanding mathematician and astronomer, who introduced the use of the secant as well as the tangent into astronomical observations.  Another Buwayhid ruler, Rukn al-Daulah, (932--76 A.  D.) patronised Abu Jafar al-Khazin, a well-known astronomer of Khorasan, who ascertained 'the obliquity of the ecliptic and solved a problem of Archimedes which leads to a cubic equation'.l

By the close of the tenth century A.D., Baghdad was thronged with hundreds of astronomers including Ali Ibn Amajur and Abul Hasan Ali Ibn Amajur who are known for their accurate calculation of the lunar movements.

Abu Abdulla Ibn Muhammad Ibn Jabir-al Battani (Albategnius-877-91 8 A.D.) a Sabian from Harran was one of the most illustrious astronomers of the East who is known as the Ptolemy of the Arabs.  His tables translated into Latin formed the basis for astronomical work in Europe for several centuries.  He also wrote a voluminous treatise on the subject and his astronomical tables were an advance over those of Khwarizmi and the Indians.  He carried on his studies and observations in al-Raqqah.  He was an outstanding original writer and a research scholar of repute who made several emendations to Ptolemy and rectified the calculations for the orbits of the moon and certain other planets.  According to Philip K.  Hitti, "He’s proved the possibility of annular eclipses of the sun and determined with greater accuracy the obliquity of the ecliptic, the length of the tropical year, end of the seasons and the mean orbit of the sun"."

Persia, which, after the downfall of the Abbasid Caliphate formed the nerve centre of Islamic learning, produced some of the greatest intellectuals of mediaeval times.  Great advances were made in almost all branches of knowledge.  One of the most outstanding intellectuals of Islam was Abu Rehan Beruni (973--1048 A.D.) who graced the literary meetings of Mahmud Ghaznaui.  "Few know physics and metaphysics" says J.  N.  Sircar, the celebrated Indian historian, "amongst those few the greatest in Asia was Al-Beruni, at once a philosopher and a scientist and preeminent in both of these two seemingly incompatible fields".' Al-Beruni was a distinguished and original scholar of astronomy and other sciences.  His Al-Qanun al-Masudi written for his patron Sultan Masud of Ghazni in 1030 A.D.  is an astronomical encyclopaedia.  A short catechism of geometry, arithmetic, astronomy and astrology also written in 1030 A.D.  and entitled Al-Tahfin li-awail sinaat al-l\rajum deals chiefly with the calenders and eras of ancient peoples.  The rotation of the earth on its axis and the accurate determination of longitudes and latitudes were also elaborately discussed in this book.

Malik Shah Saljuqi and his illustrious grand vazir Nizamul Mulk Toosi were also great patrons of learning during those times.  They established an observatory at Rayy or Neshapur in 1074-75 A.D. where under the guidance of Omar Khayyam and Abdur Rahman al-Hazini astronomical observations were made.  Their research led to a reformed calendar which preceded the Cregorian calender by 600years.  According to Sedillot, who is an authority on the subject, "it is more exact".  This calendar formulated by Omar Khayyam was named Al-Tarikh Jalali after his patron Jalaluddin Malik Shah Seljuqi, and is based on an accurate determination of the length of the tropical year.  The Gregorian calendar leads to an error of one day in 3,330 years whereas Khayyam's apparently leads to an error of one day in about 5,000 years.

The destruction wrought by the Mongol hordes served a death blow to all cultural and intellectual movements in the world of Islam.  The cultural treasures amassed during centuires of intellectual pursuits was reduced to ashes.  On the downfall of the Abbasid Caliphate there sprang up small Muslim principalities who kept aloft the candle of learning and vied with each other in the patronage of scholars and scientists.  A year after the fall of Baghdad, in 1259 A.D., Hulagu Khan started the construction of the Khaniz observatory in Maragah (Turkistan).  This was the best observatory of its time, working under the directorship of the celebrated genius and astronomer of that era, Nasiruddin Toosi, and equipped with the best available instruments including an armillary sphere, the mural quadrant and a solstitial armil.  The remains of this observatory are still extant and it was here that Toosi compiled his famous astronomical tables known as al zij' al il khani which earned much popularity throughout Asia including China.  Nasiruddin Toosi also wrote Tazkirah fi'ilm al-Hai'a', an outstanding work on astronomy.

Samarqand, the capital of the famous conqueror Tamerlane became in those days a great centre of Islamic education.  An astronomical table prepared in 1437 for a prince of the family of Tamerlane and called Table of Ulugh Beg was much appreciated in Europe and according to Carra De Vaux was published in England in the 18th century A.D.

The Arab civilization of Spain rivalled that of the Abbasid's in the East, and during the middle of the IOth century astronomical studies were especially favoured by the rulers of Muslim Spain.  The outstanding Spanish astronomers were Al-Majriti of Cordova, al-Zarqali (1029--1087 A.D.) of Toledo, Ibn Afiah (d/2140-50 A.D.) of Seville and Nur-ud-din Abu Ishaq al-Bitruji.

In his famous work Kitab al Hayat (book of astronomy), which was later translated into Latin by Gerard of Cremona, Jabir Ibn Afiah, the celebrated astronomer of the twelfth century, sharply criticised Ptolemy.  Against the observations of Ptolemy he rightly observed that the lower planets, Mercury and Venus, have no visible parallaxes.  His generalisations of the subject were confirmed by later research.

Al-Zarqali (Arzachel 1029-1087 A.D.) was the foremost astronomical observer of Muslim Spain.  He was the celebrated instrument maker who constructed an improved type of astrolabe (a saJilza) on which he wrote a treatise.  His calculations of the length of the Mediterranean Sea as 42 degrees was approximately accurate in comparison to Ptolemy's estimate of 62" and Al-Khwarizmi's estimate of 52".  He also has the distinction of being the first astronomer to prove the motion of the solar apogee with reference to stars.  His works along with those of Al-Battani were studied and.appreciated in the West and Copernicus quotes him in his well known work De Revolutionibus Orbizrm Coelestium.

Nur-ud-Din Abu Ishaq al-Bitruji (Alpetragius), was foremost among the last astronomers of Spain, whose outstanding work Kitab al-Hai'a was translated into Latin by Michael Scot in 1217 and into Hebrew in 1259 A.D.  He is considered the exponent of a new astronomy and his book marks the culmination of the anti-Ptolemaic movement.  According to Draper, "increased accuracy was given to the correction of the astronomical observations by Alhazen's great discovery of atmospheric refraction."

The first observatory in Europe was built by Arabs in Seville.  The famous astronomical tower of Seville was constructed under the supervision of Jabir Ibn Afiah in 1190 A.D.  With the fall of the Muslim power in Spain it was turned into a belfry by the Christian conquerors who did not know what else to do with it.

"Finally it was through Spanish channels" says Philip K.  Hitti, "that the Latin West found its oriental inspiration in astronomy and astrology.  The leading Muslim astronomical works were translated in Spain into Latin, and the Alfonsine tables compiled under the aegis of Alfonso X in the 13th century were but a development of Arab astronomy".l According to R..Briffault, "Arab astronomy did not forestall Copernicus or Newton, though without it there would have been no Copernicus and Newton" 2

The Muslims, have thus made the greatest contributions to astronomical knowledge during mediaeval times.

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