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Updated: June 28, 2025
In the middle of the ninth century Albategnius, a Syrian prince, improved the value of excentricity of the sun's orbit, observed the motion of the moon's apse, and thought he detected a smaller progression of the sun's apse. His tables were much more accurate than Ptolemy's. Abul Wefa, in the tenth century, seems to have discovered the moon's "variation."
In Alexandria the memory of the illustrious old times was to be recalled by the discovery of the motion of the sun's apogee by Albategnius, and the third inequality of the moon, the variation, by Aboul Wefa; to be discovered six centuries later in Europe by Tycho Brahe.
The Hollander censures all; and thus they disagree among themselves, old and new, irreconcilable in their opinions; thus Aristarchus, thus Hipparchus, thus Ptolomæus, thus Albategnius, etc., with their followers, vary and determine of these celestial orbs and bodies; and so whilst these men contend about the sun and moon, like the philosophers in Lucian, it is to be feared the sun and moon will hide themselves, and be as much offended as she was with those, and send another message to Jupiter, by some new-fangled Icaromenippus, to make an end of all these curious controversies, and scatter them abroad.
In the eleventh century another Arabian discoverer, Arzachel, observing the sun to be less advanced than Albategnius had found it, inferred incorrectly that the sun had receded in the mean time. The modern explanation of this observation is that the measurement of Albategnius was somewhat in error, since we know that the sun's motion is steadily progressive.
That in the lower left corner with an isolated mountain in the centre is Albategnius, sixty-four miles in diameter. Peaks in the ring rise to a height of fifteen thousand feet above the central plain. The mountains above and to the left are the lunar Apennines; those on the left just below the centre are the Alps. Both ranges include peaks from fifteen thousand to twenty thousand feet in height.
PARROT. An irregularly-shaped formation, 41 miles in diameter, S. of Albategnius, with a very discontinuous margin, interrupted on every side by gaps and depressions, large and small; the most considerable of which is the regular ring-plain Parrot a, on the E. An especially fine valley, shown by Schmidt to consist in part of large inosculating craters, cuts through the wall on the S.W., and runs on the E. side of Argelander towards Airy.
Albategnius is sixty-five miles across, with peaks from 10,000 to 15,000 feet in height. Sacrobosco is a confused mass of broken and distorted walls. Aliacensis is remarkable for having a peak on the eastern side of its wall which is more than 16,000 feet high.
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