چکیده
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Muḥyī al-Dīn al-Maghribī (d. 1283 AD) carried out a systematic observational
programme at the Maragha observatory in northwestern Iran in order to provide new
measurements of solar, lunar, and planetary parameters, as he explains in his treatise
Talkhīṣ al-majisṭī (Compendium of the Almagest). His project produces a new and consistent
set of parameters. On the basis of his four documented observations of Mars, carried out in
1264, 1266, 1270, and 1271 AD, he measured the unprecedented values for the radius of the
epicycle, the longitude of the apogee, and the mean motion in longitude of the planet and
also confirmed that Ptolemy’s value for its eccentricity was correct for his time. This paper
presents a detailed, critical account of Muḥyī al-Dīn’s measurements. Using a criterion
described below, we compare the accuracy of his values for the structural parameters of Mars
with that of other historically important values known for these parameters from medieval
Middle Eastern astronomy from the early eighth to the late fifteenth century. Muḥyī al-Dīn
attained a higher degree of precision in his theory of Mars established at Maragha than the
majority of his predecessors; the results were also more accurate than those established in
his earlier zīj written in Damascus in 1258 AD and used in the official astronomical tables
produced at the Maragha observatory, the Īlkhānī zīj.
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