[2] After completing his studies with Abu 'Ali al-Marrakushi, Ibn al-Shatir returned to his home in Damascus where he was then appointed muwaqqit (timekeeper) of the Umayyad Mosque.

[2] Part of his duties as muqaqqit involved keeping track of the times of the five daily prayers and when the month of Ramadan would begin and end.

[4] His first set of tables, which have been lost over time, allegedly combined his observations with those of Ptolemy, and contained entries on the Sun, Moon and Earth.

[3] Ibn al-Shatir′s most important astronomical treatise was kitab nihayat al-sul fi tashih al-usul (نهاية السول في تصحيح الاصول "The Final Quest Concerning the Rectification of Principles").

His model incorporated the Urdi lemma, and eliminated the need for an equant (a point on the opposite side of the center of the larger circle from the Earth) by introducing an extra epicycle (the Tusi-couple), departing from the Ptolemaic system in a way that was mathematically identical (but conceptually very different) to what Nicolaus Copernicus did in the 16th century.

[6] Because the Ptolemaic system contains some faulty numerical values for its observations, the actual geocentric distance of the Sun had been greatly underestimated in its solar model.

And with his numerous observations, Ibn al-Shatir was able to generate a new maximum solar equation (2;2,6°), which he found to have occurred at the mean longitude λ 97° or 263° from the apogee.

[7] This was partially done by reducing Ptolemy's circular geometric models to numerical tables in order to perform independent calculations to find the longitude of the planets.

[10] Furthermore, the exact replacement of the equant by two epicycles used by Copernicus in the Commentariolus paralleled the work of Ibn al-Shatir one century earlier.

The presence of this eastern manuscript containing the ideas of Islamic scholars in Italy provides potential evidence of transmission of astronomical theories from the East to Western Europe.

[14] The idea of using hours of equal time length throughout the year was the innovation of Ibn al-Shatir in 1371, based on earlier developments in trigonometry by al-Battānī.

Each day was split into twelve equal segments which meant that the hours would have been shorter in the winter and longer in the summer due to the activity of the sun.

[15][16] Ibn al-Shatir also invented a timekeeping device called "Sandūq al‐Yawāqīt li maʿrifat al-Mawāqīt" (صندوق اليواقيت لمعرفة المواقيت jewel box), which incorporates both a universal sundial and a magnetic compass.

[17] The "Sandūq al‐Yawāqīt li maʿrifat al-Mawāqīt" had a moveable hole in it which allowed the user to find the hour angle of the sun.