- The Astrolabe was a device used in Celestial Navigation to calculate the user’s Latitude and local time. Astrolabe means ‘star-taker’ in Greek.
- The Astrolabe superseded the Gnomon, by bringing together the Gnomon and the Star Chart, built into one instrument.
History
- c.160 BCE
- The concept of the Astrolabe is credited as an invention by the Greek Astronomer Hipparchus, born in 180 BCE. However, it is uncertain whether he ever built one.
- 150 CE
- The Astronomer Ptolemy of Alexandria, published ‘Planisphaerium’, which described the mathematical calculations needed to project the stars on to the celestial sphere. This appears to be a guide to constructing an Astrolabe, but there is no proof that he built one, although he did build an Armillary Sphere.
- 390 CE
- Theon of Alexandria wrote a description of how to build an Astrolabe.
- c.700 CE
- From the eighth century onwards, the Arab Astronomers start making Astrolabes.
- c.1390 CE
- Geoffrey Chaucer wrote a Treatise on the Astrolabe.
How the Astrolabe worked
- The pointer could be rotated to align with a known star or planet.
- It was used to locate and predict the positions of the Planets and Stars in Celestial Navigation.
- The Astrolabe could calculate the user’s Latitude, and then the local time.
Source
- Treatise on the Astrolabe by Geoffrey Chaucer c.1390 CE.
Jacob's staff
- The Jacob’s staff is a simple device that was first recorded as being used in Europe to measure angles between the Horizon and a celestial body during the 14th century CE.
- It was replaced by the Sextant.
Museums
- Oxford Museum of the History of Science
- The Museum holds many examples of the Astrolabe.
- Whipple Museum, Cambridge
- The Museum holds examples of Astrolabes in its Holden-White Collection.
History of Science Museum, Oxford