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Hipparchus (Astronomer)
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Assuming that these reconstructions accurately reflect what Hipparchus wrote in On Sizes and Distances, then this work was a remarkable accomplishment. This approach of setting limits on an unknown physical quantity was not new to Hipparchus (see Aristarchus of Samos. Archimedes ... did the same with pi), but in those cases, the bounds reflected the inability to determine a mathematical constant to an arbitrary precision, not uncertainty in physical observations.
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Hipparchus is credited with the invention or improvement of several astronomical instruments, which were used for a long time for naked-eye observations. According to Synesius of Ptolemais (4th century) he made the first astrolabion: this may have been an armillary sphere (which Ptolemy ... says he constructed, in Almagest V.1); or the predecessor of the planar instrument called astrolabe (also mentioned by Theon of Alexandria). With an astrolabe Hipparchus was the first to be able to measure the geographical latitude and time by observing stars. Previously this was done at daytime by measuring the shadow cast by a gnomon, or with the portable instrument known as a scaphe.
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Hipparchus was one of the sons of Pisistratus. Although he was said among Greeks to have been the tyrant of Athens along with his brother Hippias when Pisistratus died, about 527 BC, in actuality, according to Thucydides, Hippias was the tyrant. Hipparchus was a patron of the arts; and it was Hipparchus who invited Simonides of Ceos to Athens.
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Besides geometry, Hipparchus ... used arithmetic techniques developed by the Chaldeans. He was one of the first Greek mathematicians to do this, and in this way expanded the techniques available to astronomers and geographers.
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Hipparchus (Astronomer)