Contributions of Ancient Arabian and Egyptian Scientists on Astronomy - Part 3

By: Md. Wasim Aktar
Deptt. of Agril. Chemicals, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia, West Bengal, India.

‘Ali Ibn ‘Isa al-Astur1ãbi who flourished in Baghdad and Damascus in the first half of the 9th century, took part in the measurement of the length of the terrestrial degree ordered by al-Ma’mun. He made astronomical observations at Baghdad and Damascus from 829 to 833. He was the famous constructor of astrolabes; hence the nickname al-Asturlãbi (maker of astrolabe). He wrote a treatise on astrolabes, which is one of the earliest works on this instrument. (14)

Yahya Ibn Abi Mansür also took part in the observations made at Baghdad in 829-30, and compiled the astronomical tables called Ma’munic tables. Like the tables of Habash these, too, are a collective work of ‘various astronomers. Al-Marwarudhi, who also flourished under al-Ma’mun, made solar observations. (15)

In the 9th century astronomy flourished in the East, Astronomical researches were conducted in the observatories of Baghdad, Damascus and other places. More original and improved work was done in the second half of the 10th century. The elaboration of trigonometry, which was considered to be a branch of astronomy at that time, was also continued. A great attention was paid to the construction of good astronomical instruments, especially to the spherical astrolabe which was newly introduced at that time. Hamid Ibn ‘Ali was a famous constructor of spherical astrolabes. Jãbir Ibn Sinan was also a maker of this as well as of other astronomical instruments. According to al-Biruni, he was the first to make a spherical astrolabe. Al-Nairizi wrote on this instrument an elaborate treatise which represents the best Arabic work on this topic. In this treatise the author, after giving the introduction, describes the instruments, and gives its applications. Beside this work, al-Nairizi compiled astronomical tables. A great scientist al-Mähani made for 33 years (833—886), a series of observations on lunar and solar eclipses and planetary conjunctions. Another astronomer of this time Ahmad al- Nahâwandi, who flourished at the time of Yahya Ibn Khalid Ibn Barmak, made astronomical observations at Jundishapur and compiled tables called Mushtamil. (16)

After carrying out astronomical observations for ten years (825 to 835) Habash al-Hãsib compiled three astronomical tables. The first were according to the Hindu method (based on Siddhanta). The second called Al-Zij al-Mumtahan (the “tested Tables”) were according to the Arab method. They were very important and were probably due to the co-operative efforts of al-Ma’mun’s astronomers. The third called Al-Zij Al-Saghir (the small tables) was commonly known as the Tables of Shah. Habash al-Hãsib determined the time of the solar eclipse of the year 829. He was the first to determine time by an altitude (in this case, of the sun). This method was generally accepted and adopted by Muslim astronomers. (17)

The most illustrious scholar of this age, and one of the greatest astronomers of Islam, was ‘Abd Allah Muhammad Ibn Jãbir Ibn Sinan al-Battãni (Latin; Albategnius, Albatenius). His ancestors were Sabeans of Harran, but he himself was a Muslim. He carried out astronomical observations of a wide range and with remarkable accuracy for about 41 years (877—918). He determined many astronomical co-efficients, like the precession 54.5” a year, inclination of the ecliptic 23° 35’, with great accuracy. He noticed an increase of 16° 47’ in the longitude of the sun’s apogee since Ptolemy’s time. This led to the discovery of the motion of the solar apsides and of slow variation in the equation of time. Al-Battãni proved the possibility of the annular eclipses of the sun. He also wrote many astrological works. His main work is a large astronomical treatise including the astronomical tables. His tables contain a catalogue of fixed stars for the year 880—81. His work is an advance on that of al-Khwãrizmi, and shows more divergence from Indian methods. Observations regarding the first appearance of the new moon, the length of the tropic and sidereal year, the obliquity of the ecliptic, the lunar anomalies, the parallaxes, etc., are more complicated and more accurately made by al-Battãni than by al-Khwãrizmi

Al-Battãni’s astronomical treatise was translated into Latin and Spanish in the 12th and 13th centuries respectively. It exerted a great influence on the European scholars of the middle Ages and Renaissance. (l8)

Thãbit Ibn Qurrah (d. 901) who was a physician, mathematician, astronomer and translator from Greek and Syriac into Arabic published his solar observations made at Baghdad. He particularly determined the altitude of the sun and the length of the solar year. (19)