Al-Zarqali

Abū Isḥāq Ibrāhīm ibn Yaḥyā al-Naqqāsh al-Zarqālī al-Tujibi (); also known as Al-Zarkali or Ibn Zarqala (1029–1100), was an Arab maker of astronomical instruments and an astrologer from the western part of the Islamic world. In Latin he was referred to as Arzachel or Arsechieles, a modified form of Arzachel, meaning 'the engraver'. He lived in Toledo, Al-Andalus before moving to Córdoba later in his life. His works inspired a generation of Islamic astronomers in Al-Andalus, and later, after being translated, were very influential in Europe. His invention of the Saphaea (a perfected astrolabe) proved very popular and was widely used by navigators until the 16th century.

The crater Arzachel on the Moon is named after him. was born in a village near the outskirts of Toledo, the then capital of the newly established Taifa of Toledo. He started work after 1048 under Said al-Andalusi for the Emir Al-Mamun of Toledo and also under Al-Mu'tamid of the Taifa of Seville. Assuming a leading position under Said, Al-Zarqālī conducted solar observations for 25 years from 1050.

thumb|left|Art from [[Toledo, Spain|Toledo in Al-Andalus depicting the Alcázar in the year 976.AD]]

He was trained as a metalsmith and due to his skills he was nicknamed Al-Nekkach "the engraver of metals". His Latinized name, 'Arzachel' is formed from the Arabic al-Zarqali al-Naqqash, meaning 'the engraver'.

Science

thumb|upright|right|A copy of al-Zarqālī's [[astrolabe as featured in the Calahorra Tower.]]

Instruments

Al-Zarqālī wrote two works on the construction of an instrument (an equatorium) for computing the position of the planets using diagrams of the Ptolemaic model. These works were translated into Spanish in the 13th century by order of King Alfonso X in a section of the Libros del Saber de Astronomia entitled the "Libros de las laminas de los vii planetas".

He also invented a perfected kind of astrolabe known as "the tablet of al-Zarqālī" (al-ṣafīḥā al-zarqāliyya), which was famous in Europe under the name Saphaea.

There is a record of an al-Zarqālī who built a water clock, capable of determining the hours of the day and night and indicating the days of the lunar months. According to a report found in al-Zuhrī's Kitāb al-Juʿrāfīyya, his name is given as Abū al-Qāsim bin ʿAbd al-Raḥmān, also known as al-Zarqālī, which has made some historians think that this is a different person. Al-Zarqālī's model for the motion of the Sun, in which the center of the Sun's deferent moved on a small, slowly rotating circle to reproduce the observed motion of the solar apogee, was discussed in the thirteenth century by Bernard of Verdun and in the fifteenth century by Regiomontanus and Peurbach. In the sixteenth century Copernicus employed this model, modified to heliocentric form, in his De Revolutionibus Orbium Coelestium.

Tables of Toledo

Al-Zarqālī also contributed to the famous Tables of Toledo, an adaptation of earlier astronomical data by Al-Khwarizmi and Al-Battani, to locate the coordinates of Toledo. This almanac that he compiled directly provided "the positions of the celestial bodies and need no further computation", it further simplifies longitudes using planetary cycles of each planet.

In designing an instrument to deal with Ptolemy's complex model for the planet Mercury, in which the center of the deferent moves on a secondary epicycle, al-Zarqālī noted that the path of the center of the primary epicycle is not a circle, as it is for the other planets. Instead it is approximately oval and similar to the shape of a pignon (or pine nut). Some writers have misinterpreted al-Zarqālī's description of an earth-centered oval path for the center of the planet's epicycle as an anticipation of Johannes Kepler's sun-centered elliptical paths for the planets. Although this may be the first suggestion that a conic section could play a role in astronomy, al-Zarqālī did not apply the ellipse to astronomical theory and neither he nor his Iberian or Maghrebi contemporaries used an elliptical deferent in their astronomical calculations.

Works

Major works and publications:

Al Amal bi Assahifa Az-Zijia
Attadbir
Al Madkhal fi Ilm Annoujoum
Rissalat fi Tarikat Istikhdam as-Safiha al-Moushtarakah li Jamiâ al-ouroud
Almanac Arzarchel

Notes

External links

Muslim Scientists Before the Renaissance: Abū Ishāq Ibrāhīm al-Zarqālī (Arzachel)
'Transmission of Muslim astronomy to Europe'
'An Extensive biography'