Equatorium
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An equatorium (plural, equatoria) is an
History
In his comment on Ptolemy's Handy Tables, 4th century mathematician Theon of Alexandria introduced some diagrams to geometrically compute the position of the planets based on Ptolemy's epicyclical theory. The first description of the construction of a solar equatorium (as opposed to planetary) is contained in Proclus's fifth-century work Hypotyposis,[1] where he gives instructions on how to construct one in wood or bronze.[2]
The earliest known descriptions of planetary equatoria are in the Latin translation of an early eleventh century text by
The Theorica Planetarum (c. 1261–1264) by Campanus of Novara is the earliest extant description of the construction of an equatorium in Latin Europe.[4] Campanus' instrument resembled an astrolabe, with several interchangeable plates within a mater. The best manuscripts of Campanus' treatise contain paper and parchment equatoria with moveable parts.[2]
Variations
The history of the equatorium does not just end after the 11th century, but it inspired a more diverse invention called “The Albion”. The Albion is an astronomical instrument invented by Richard of Wallingford at the beginning of the 14th century.[5] It has various functional uses such as that of the equatorium for planetary and conjunction computations. It can calculate when eclipses will occur. The Albion is made up of 18 different scales which makes it extremely complex in comparison to the equatorium. The history of this instrument is still disputed to this day, as the only Albion from the past is both unnamed and unmarked.[5]
Astrolabe compared with equatorium
The roots of the equatorium lie in the astrolabe. The history of the astrolabe dates back to roughly 220 BC in the works of Hipparchus.[6] The difference between the two instruments is that the astrolabe measures the time and position of the sun and stars at a specific location in time.[7] In contrast, the equatorium is used to calculate the past or future positions of the planets and celestial bodies according to the planetary theory of Ptolemy.[citation needed]
Uses
The equatorium can further be specialized depending on the
At least 15 minutes was needed to calculate the planetary position with the use of a table for each celestial body.[9] A horoscope of that era would have required the positions of seven astronomical objects, requiring nearly two hours of manual calculation time.
See also
- Antikythera mechanism
- Armillary sphere
- Astrarium
- Astrolabe
- Astronomical clock
- Orrery
- Planetarium
- The Equatorie of the Planetis
- Torquetum
References
- Teubner.
- ^ ISBN 978-0-19-509539-5.
- ^ "Zarqali". islamsci.mcgill.ca. Retrieved 2018-05-09.
- ISBN 978-0-684-10114-9.
- ^ a b Truffa, Giancarlo. "The Albion of Rome. A unique example of Medieval Equatorium".
- ^ "Third Solution: The Equant Point - SliderBase". www.sliderbase.com. Retrieved 2018-05-09.
- ^ "the definition of astrolabe". Dictionary.com. Retrieved 2018-05-09.
- JSTOR 43816789.
- ISBN 978-1-4419-9916-0.