Aristarchus claimed that at half moon (first or last quarter moon), the angle between the Sun and Moon was 87°.Greek Mathematical Works, Loeb Classical Library, Harvard University, 1939–1941, edited by Ivor Thomas, volume 2 (1941), pp. 6–7 He may have proposed 87° as a lower bound, since gauging the lunar terminator's deviation from linearity to one degree of accuracy is beyond the unaided human ocular limit (which is about three arcminutes of accuracy). Aristarchus is known to have studied light and vision as well.Heath, 1913, pp. 299–300; Thomas, 1942, pp. 2–3.
Aristarchus claimed that at half moon (first or last quarter moon) the angle between the Sun and Moon was 87°.Greek Mathematical Works, Loeb Classical Library, Harvard University, 1939–1941, edited by Ivor Thomas, volume 2 (1941), pp. 6–7 He may have proposed 87° as a lower bound, since gauging the lunar terminator's deviation from linearity to one degree of accuracy is beyond the unaided human ocular limit (which is about three arcminutes of accuracy). Aristarchus is known to have studied light and vision as well.Heath, 1913, pp. 299–300; Thomas, 1942, pp. 2–3.