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23.
Al-Zarqali
(420-480H/1029-1087AD)
Al-Zarqali was the foremost astronomers of his time. He was
also a unique reference in algebra, astronomy and astrology.
He was an Arab Muslim from Andalusia, born in Toledo, where
he carried out most of his astronomic observations; then he
moved to Cordoba, where he spent the rest of his life(139).
His
full name is Ibrahim ibn Yahya an-Nakash, known as ibn
Zarqala or al-Zarqali. His Latinised name is Arzaquiel.
Scientific Contributions
Al-Zarqali
invented a new astrolabe, known as Safihah Zarqalia and
referred to in astronomy as "al-Zarqali astrolabe". In the
15th century, Ragio Montanous published a manuscript in
which he detailed the advantages of Sahifa al-Zarqalia. Al-Zarqali
was the first to prove the motion of the apogee of the Sun
relative to the stars. He measured its rate motion as 12.04
minutes per year (the actual value is 11.8 minutes)(140).
Al-Zarqali
also compiled tables on planets, known as Toledan Tables,
based on the observations he made in Toledo from 1061 to
1080(141).
Al-Zarqali
corrected geographical data from Ptolemy and al-Kawarizmi.
Specifically, he corrected Ptolmey’s estimate of the length
of the Mediterranean sea from 62 degrees to the correct
value of 42 degree(142).
When talking on the influence of Arab astronomers in the
West, Hunkah says that al-Zarqali’s works were carefully
studied by Western scholars. In the 12th century, Gerard of
Cremonia translated al-Zarqali’s works into Latin. Ragio
Montanous wrote a book in the 15th century on the advantages
of the Sahifah al-Zarqalia. In 1530, the German scholar
Ziegler Jacob wrote a commentary on al-Zarqali’s book. In
his "De Revolutionibus Orbium Coelestium" -1530-, Copernicus
quotes the works of al-Zarqali and al-Battani (Albategnius)(143).
Major
Works
Zarkali
cites the following among al-Zarqali’s major works :
-"Al Amal bi Assahifa Az-Zijia";
-"Attadbir";
-"Al Madkhal fi Ilm Annoujoum";
-"Rissalat
fi Tarikat Istikhdam as-Safiha al-Moushtarakah li Jamiā al-ouroud";
Al-Zarqali’s
works influenced Spanish astronomers who designed the
"Alfonso's Tables", by the name of Alfonso, king of Castile,
who, 200 years after al-Zarqali’s death, ordered all his
works to be translated into Castillan(144).
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