Hipparchus invents the astrolabe It is probable that the astrolabe was invented by the Greek astronomer Hipparchus, who devised a plane astrolabe around 200 BC. Its purpose was to tell the time at night by determining the angular distance between stars. Astrolabes were used by astronomers throughout antiquity in the Greco-Roman world. Eventually, they were introduced to the Islamic world by the 8th century AD. It is likely that the Islamic world’s version of the astrolabe was then, around 1000 AD, introduced to Christian Europe, where such instruments were used until the early modern period (around 1550–1770). As mechanical clocks became more widely available in the 17th and 18th centuries, the astrolabe gradually fell out of use. Read more about the astrolabe in the Clocktime article The first timekeepers: Telling time before the pendulum clock. Image Credits Hipparchus, Greek astronomer and mathematician. F033/2687 Science Source / Science Photo Library. Islamic Astrolabe, Unsigned without date, 901-1100 CE, Science Museum Group Collection © The Board of Trustees of the Science Museum, CC BY-NC-SA 4.0, https://collection.sciencemuseumgroup.org.uk/objects/co57101/islamic-astrolabe-astrolabe
