Lesser Known Astronomical Instruments
Triquetrum- A precursor to the telescope, the triquetrum was the name for parallactic rulers described by Ptolemy in the Almagest and used to measure the altitude of celestial objects. It was one of the most popular astronomical instruments, and could measure angles much more accurately than an astrolabe. It’s also mentioned by Copernicus in his book, De Revolutionibus Orbium Coelestium, written in 1543, and was used by the Danish astronomer Tycho Brahe.
Torquetum- The exact origins of the torquetum are unclear, though Franco of Poland is credited with discussing and distributing information about the instrument first with his earliest writings on it dating back to 1284, though the only surviving examples date back to the 16th century. The torquetum was an instrument used to measure the position of celestial objects in either elliptical, equatorial, or terrestrial coordinate systems. In a sense, it’s a complex medieval analog computer.
Equatorium- Inspired by the astrolabe, an equatorium was used to work out the past, present, and even future positions of the sun, moon, and planets according to the planetary theory of Ptolemy. It’s one of the more rare astronomical instruments, with only a few surviving in museum collections. This one is from around 1600, possibly French in origin, and is on display at the World Museum in Liverpool.
