This mechanism, which is alleged to have excited great wonder in the West, furnishes yet another instance of Arabian practicality.
Perhaps the greatest of the Arabian astronomers was Mohammed ben Jabir Albategnius, or El-batani, who was born at Batan, in Mesopotamia, about the year 850 A.D., and died in 929.

Albategnius was a student of the Ptolemaic astronomy, but he was also a practical observer.

He made the important discovery of the motion of the solar apogee.

That is to say, he found that the position of the sun among the stars, at the time of its greatest distance from the earth, was not what it had been in the time of Ptolemy.

The Greek astronomer placed the sun in longitude 65 degrees, but Albategnius found it in longitude 82 degrees, a distance too great to be accounted for by inaccuracy of measurement.