ABU ABDULLAH ALBATTANI (ALBATEGNIUS) (858  929
C.E.)
AlBattani, known in the West as Albategnius, was a
famous astronomer and mathematician. He has been recognized
as the greatest astronomer of his time and one of the
greatest of the Middle Ages. Abu Abdullah Muhammad Ibn
Jabir Ibn Sinan alBattani was born around 858 C.E.
in or near Battan, a state of Harran. He belonged to
the princely Sa'bi family of Harran and he was a Muslim.
AlBattani was first educated by his father Jabir Ibn
Sin'an alBattani, who was also a wellknown scientist.
He then moved to Raqqa, situated on the bank of the
Euphrates, where he received advanced education in sciences.
At the end of the ninth century, he migrated to Samarra,
where he worked until his death in 929 C.E.
AlBattani made his observations and studies in AlRaqqah
from 877 to 929 and made many important discoveries
in astronomy. According to Prof. Phillip Hitti, "He
made several emendations to Ptolemy and rectified the
calculations for the orbits of the moon and certain
planets. He proved the possibility of annular eclipses
of the sun and determined with greater accuracy the
obliquity of the seasons and the true and mean orbit
of the ecliptic, the length of the tropical year and
the seasons and the true and mean orbit of the sun."
His remarkably accurate calculation of the solar year
as 365 days, 5 hours, 46 minutes and 24 seconds is very
close to the latest estimates. He found that the longitude
of the Sun's apogee had increased by 16o 47' since Ptolemy.
It inferred the important discovery of the motion of
solar apsides and of a slow variation in the equation
of time. He did not believe in the trepidation of the
equinoxes, although Copernicus, several centuries later,
held that erroneous notion.
In a sharp contrast to Ptolemy, AlBattani proved the
variation of the apparent angular diameter of the sun
and the possibility of annular eclipses. He revised
orbits of the Moon and the planets and proposed a new
and very ingenious theory to determine the conditions
of visibility of the new moon. Dunthorne, in 1749, used
AlBattani's excellent observations of the lunar and
solar eclipses to determine the acceleration of motion
of the moon. He determined many astronomical coefficients
with great accuracy: Prescession of Equinoxes 54.5"
a year and inclination of the Ecliptic 23o 35'. AlBattani
also provided very ingenuous solutions for some problems
of spherical trigonometry using the methods of orthographic
projection. It was from a perusal of AlBattani's work
on apparant motion of fixed stars that Hevilius discovered
the circular variation of the moon.
AlBattani's greatest fame came in Mathematics with
the use of trigonometric ratios as we used them today.
He was the first to replace the use of Greek chords
by Sines, with a clear understanding of their superiority.
He also developed the concept of Cotangent and furnished
their tables in degrees.
Joseph Hell remarked that "in the domain of trigonometry
the theory of Sine, Cosine and tangent is an heirloom
of the Arabs. The brilliant epochs of Peurbach, of Regiomontanus,
of Copernicus, cannot be recalled without reminding
us of the fundamental and preparatory labor of the Arab
Mathematician."
AlBattani wrote many books on astronomy and trigonometry.
His most famous book was an astronomical treatise with
tables, which was translated into Latin in the twelfth
century and is known by the title 'De Scienta Stellarum
 De Numeris Stellarum et motibus.' The third chapter
of his book on Astronomy is devoted to Trigonometry.
An old translation of this book is available at the
Vatican. His another book alZij was published by C.A.
Nullino in Rome in 1899. His treatise on astronomy was
extremely influential in Europe until the Renaissance
and was translated in several languages.
Beer and Madler in their famous work Der Mond (1837)
mention one of the surface features of the moon after
AlBattani (Albategnius). It is the name of a plain
eighty miles in diameter in Section No. 1, surrounded
by mountains ten to fourteen thousand feet high, several
craters and several saucershaped pits. AlBattani's
original discoveries both in Astronomy and Trigonometry
were of great consequence to the development of sciences,
particularly in the Middle Ages. Copernicus in his book
'De Revolutionibus Orbium Clestium' expresses his indebtedness
to AlBattani.
