Contributions of Ancient Arabian and Egyptian Scientists on Astronomy - Part 6

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

Näsir al-Din made observations in the observatory at Maragha which was well equipped with good astronomical instruments. He prepared new astronomical tables called after the Mongol ruler, Al-Zij al-Ilkhäni. Nasir al-Din asked the ruler to give him a period of 30 years to compile the tables, because it was the shortest period during which the planetary cycles were completed. But the ruler refused, and gave him only 12 years to accomplish this task. Nasir al-Din tried a succeeded in completing the tables within this time. They were based upon new observations. But the use of the earlier ones had also been made.

The Zij-i- Ilkhäni was originally written in Persian. It consists of four books dealing respectively with (a) Chinese, Greek, Arabic and Persian Chronology; (b) motions of the planets; (c) ephemeredes and (d) astrological operations. The translation of the Zij was made into Arabic, and commentaries on it were written. Finally, a sort of supplement to it was compiled by Jamshed Ibn Mas’üd al-Käshi (d. 840/1436), the first director of Ulugh Beg’s observatory in Samarqand. These tables enjoyed a great popularity in the East including China, and were, continued to be used even after the compilation of new tables by Ulugh Beg in 1437. (29)


A contemporary of Nasir al-Din, Mu’ayyid al-Din al-Urdi al-Dimashqi also took part with him in compiling the tables. He was a Syrian astronomer, architect and engineer. He started his career as a technician in Syria. He did some hydraulic work in Damascus, and also constructed there an astronomical instrument for al-Mansür Ibrahim (King of Hims, 1239—1245). In about 1259 he went to Maragha, and helped Nasir al-Din in organizing the observatory and compiling the tables. It seems that the instruments, remarkably precise, were constructed under his supervision in the foundry attached to the observatory.

Al-Urdi was the author of a treatise in which he also described the instruments used in the observatory of Maragha, and explained their use and construction. The instruments are as follows:—
(1) mural quadrant (2) armillary sphere (3) solstitial armil (4) equinoctial armil (5) Hipparch’s diopter (alidade); (6) instrument with two quadrants (7) instrument with two limbs (8) instruments to determine sines and azimuths (9) instruments to determine sines and versed sines, (10) the perfect instrument (a universal instrument) (11) parallactic ruler (after Ptolemy).

Al-Urdi was also the author of two other treatises; one on the construction of a perfect sphere and another on the determination of the distance between the centre of the sun and the apogee. He compiled astronomical tables, and wrote on Ptolemaic astronomy.

In 1279 or 1289 al-Urdi’s son Muhammad made a celestial globe. It consisted of two brass hemispheres separated by the ecliptic. Its diameter was 140 mm. It had a horizon circle. Two movable half circles were attached to the zenith point by a pivot. These circles are graduated and are used to determine the declination and right ascension of any star. Forty-eight constellations, the equator and the ecliptic are inlaid with silver or gold. It is preserved in the mathematical salon of Dresden. (30)

The works of Muslim astronomers were later translated into Latin, Hebrew and vernaculars by the Christian and Jewish scholars, some of the technical terms including azimuth (al-Samt), Algol (Alfol), Achernar (Akhir al-Nahr), passed into the European languages. The names of many stars such as akrab (Aqrab), Algedi (al-Jadi, the kid), Altair (al-ta’ir ,the player), Denab (dhanb, tail), Pherkad (Farqad, calf), Adara (‘Adhrah) Aldebaran (al-dibràn), which are of Arabic origin, also passed into these languages. The stars being countless in number, their separate study is not possible. They were, therefore, divided into various groups, and the groups were named after the things and animals with which they resembled.

REFERENCES :

1. Briffault, Robert , The Making of’ Humanity, Lahore, 1980, p. 187.
2. Encyclopedia Britannica, London, Vol. II, p.575.
3. Abu’l Hasan Ali Ibn Yusuf , Al-Qifti , Tàrikh al-Hikmah,’ Leipzig, 1903, p. 265. Sarton, George, Introduction to the History of Science, Washington 1927, vol. I. p. 530.
4. Ibid.
5. Ibid, p. 563.
6. Al-Qifti, op. cit., 57.
7. Ibid., p. 327.Sarton, op. cit. p. 531.
8. Ibid.
9. Ibid. p. 557.Haji Khalifah, Kashf al-Zunün, Istanbul, 1943, vol. II, p. 1594.
10. Sarton, op. cit., p. 562.
11. Ibid, p. 558.
12. Shibli Nu’mani, Al-Ma’mun, Agra, 1894, pp. 49— 50,
13. Ibn Nadeem, Al-Fehrist, Matba’ah al-Rahmaniyah, Cairo, n.d.. p. 383.
14. Shibli Nu’mani, op. cit. pp. 49—50. Sarton, op. cit. p. 566.
15. Ibid.
16. Sarton, op. cit.. p. 585.
17. Al-Qifti, op. cit. p. 170.
18. Ibid, p. 280. Sarton, op. cit. p. 5858.
19. Ibid., p. 599.
20. Al-Qifti, op. cit. p. 351.
21. Sarton, op. cit. p. 666.
22. Ibid.
23. A1-Süfi, ‘Abd al-Rahman, Swar al-Kawàkib, Hyderabad, preface by M. Nizamuddin, and J.J. Winter, pp. 1-7.
24. Al-Qifti, op. cit., p. 226.
25. A1-Qifti, op. cit., p. 230.
26. Sarton, op. cit., p. 758,
27 Ibid., p.759
28. Ibid, vol. II, part I, p. 206.
29. Ibid., part I, p. 204.
30. Al-Baghdadi, Isma’il Bãshã, Hadiyyat al-‘Arifin, Istanbul, 1951, vol. II, p. 131.
31. Sarton, op. cit. vol. II, part II, p. 1005.
32. Ibid., pp. 1013-1014.