Tanbih al-naqqad ala ma fi al-hay'a al-mashhura min al-fasad

"Tanbih al-naqqad ala ma fi al-hay'a al-mashhura min al-fasad" ("A Note of the Reviewer on the Corruption in the Well-known Astronomy") is a treatise by Gars al-Din ibn Ahmad ibn Khalil al-Halabi, written in 958 AH (1551) according to its colophon; the title shows its author's dissatisfaction with the "well-known" astronomy. ¹

In a chapter on the accidental motion of the celestial bodies and spheres the author defends the older view against a newer one that may have tried to explain the various motions of the spheres by an all-embracing rotation about the axis of the universe, with the ship analogy as the guiding idea. ¹ Elsewhere he rejects the equant and the eccentric deferent, cites Ibn al-Shatir and Mu'ayyad al-Din al-Urdi, finds the observed diameters of Venus and Mars at odds with the accepted theory, and reports from navigators that the inhabited north reaches 72 degrees. ²