パップス
Ptolemy mentions ("Almagest" V.14) that he used a similar instrument as Hipparchus, called "dioptra", to measure the apparent diameter of the Sun and Moon. Pappus of Alexandria described it (in his commentary on the "Almagest" of that chapter), as did Proclus ("Hypotyposis" IV). It was a 4-foot rod with a scale, a sighting hole at one end, and a wedge that could be moved along the rod to exactly obscure the disk of Sun or Moon.