An imprecise but systematic determination of the magnitude of objects was introduced by which Greek astronomer, geographer, and mathematician?
Magnitude (astronomy) In astronomy, magnitude is a logarithmic measure of the brightness of an object, measured in a specific wavelength or passband, usually in the visible or near-infrared spectrum. An imprecise but systematic determination of the magnitude of objects was introduced in ancient times by Hipparchus.
Hephaestion of Thebes Hephaestion, Hephaistion, or Hephaistio of Thebes (Ancient Greek: Ἡφαιστίων , "Hēphaistíōn") was a Hellenized Egyptian astrologer of late Antiquity who wrote a Greek treatise known as the "Apotelesmatics" or "Apotelesmatika" around  415. Much of the work appears to be an attempt to synthesize the earlier works of the 1st century astrologer Dorotheus of Sidon and the 2nd century astrologer Claudius Ptolemy. Hephaestion is seen mainly as one of the later compilers of the Hellenistic tradition of astrology since he mainly draws from earlier astrologers, including Antiochus of Athens, and he summarizes large portions of Ptolemy and Dorotheus, which is helpful to modern scholars since we have no other record of many of the authorities that he quotes.