Question: An imprecise but systematic determination of the magnitude of objects was introduced by which Greek astronomer, geographer, and mathematician?

Context paragraphs:
Photographic magnitude: Before the advent of photometers which accurately measure the brightness of astronomical objects, the apparent magnitude of an object was obtained by taking a picture of it with a camera.  These images, made on orthochromatic photoemulsive film or plates, were more sensitive to the blue end of the visual spectrum than the human eye or modern photometers.  As a result, bluer stars have a lower (i.e. brighter) photographic magnitude than their modern visual magnitude, because they appear brighter on the photograph than they do to modern photometers.  Conversely, redder stars have a higher (i.e. fainter) photographic magnitude than visual magnitude, because they appear dimmer.  For example, the red supergiant star KW Sagittarii has a photographic magnitude of 11.0 to 13.2 but a visual magnitude of about 8.5 to 11.  It is also common for star charts to list a blue magnitude (B) such as with S Doradus and WZ Sagittae.

Eudoxus of Cnidus: Eudoxus of Cnidus ( ; Greek: Εὔδοξος ὁ Κνίδιος , "Eúdoxos ho Knídios"; c. 390– c. 337 BC) was a Greek astronomer, mathematician, scholar and student of Plato.  All of his works are lost, though some fragments are preserved in Hipparchus' commentary on Aratus's poem on astronomy.  Theodosius of Bithynia's important work, "Sphaerics", may be based on a work of Eudoxus.

Hipparchus: Hipparchus of Nicaea ( ; Greek: Ἵππαρχος, "Hipparkhos" ;  ) was a Greek astronomer, geographer, and mathematician.  He is considered the founder of trigonometry but is most famous for his incidental discovery of precession of the equinoxes.

Autolycus of Pitane: Autolycus of Pitane (Greek: Αὐτόλυκος ὁ Πιταναῖος ; c. 360 – c. 290 BC) was a Greek astronomer, mathematician, and geographer.  The lunar crater Autolycus was named in his honour.

Conon of Samos: Conon of Samos (Greek: Κόνων ὁ Σάμιος , "Konōn ho Samios"; c. 280 – c. 220 BCE) was a Greek astronomer and mathematician.  He is primarily remembered for naming the constellation Coma Berenices.

Callippus: Callippus ( ; Ancient Greek: Κάλλιππος ; c. 370 BC – c. 300 BC) was a Greek astronomer and mathematician.

Evaluation: systematic determination of a subject's merit, worth and significance, using criteria governed by a set of standards.  It can assist an organization, program, project or any other intervention or initiative to assess any aim, realisable concept/proposal, or any alternative, to help in decision-making; or to ascertain the degree of achievement or value in regard to the aim and objectives and results of any such action that has been completed.  The primary purpose of evaluation, in addition to gaining insight into prior or existing initiatives, is to enable reflection and assist in the identification of future change.

Absolute magnitude: Absolute magnitude is a measure of the luminosity of a celestial object, on a logarithmic astronomical magnitude scale.  An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if were viewed from a distance of exactly 10 parsecs (32.6 light years), with no extinction (or dimming) of its light due to absorption by interstellar dust particles.  By hypothetically placing all objects at a standard reference distance from the observer, their luminosities can be directly compared on a magnitude scale.  As with all astronomical magnitudes, the absolute magnitude can be specified for different wavelength ranges corresponding to specified filter bands or passbands; for stars a commonly quoted absolute magnitude is the absolute visual magnitude, which uses the visual (V) band of the spectrum (in the UBV photometric system).  Absolute magnitudes are denoted by a capital M, with a subscript representing the filter band used for measurement, such as M for absolute magnitude in the V band.

Ptolemy: Claudius Ptolemy ( ; Greek: Κλαύδιος Πτολεμαῖος , "Klaúdios Ptolemaîos" ] ; Latin: "Claudius Ptolemaeus" ; c. 170 ) was a Greco-Roman mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology.  He lived in the city of Alexandria in the Roman province of Egypt, wrote in Koine Greek, and held Roman citizenship.  The 14th-century astronomer Theodore Meliteniotes gave his birthplace as the prominent Greek city Ptolemais Hermiou (Greek: Πτολεμαΐς ‘Ερμείου ) in the Thebaid (Greek: Θηβαΐδα [Θηβαΐς] ).  This attestation is quite late, however, and, according to Gerald Toomer, the translator of his "Almagest" into English, there is no reason to suppose he ever lived anywhere other than Alexandria.  He died there around AD 168.

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.

Supporting paragraphs: Magnitude (astronomy) Hipparchus
Answer: Hipparchus