Objekt 25
Ten inch mirror sextant
Description
The name sextant comes from the division of the measuring scale: one sixth of a full circle, i.e. 60°. With a mirror sextant, the measuring range is twice as large due to the mirroring, so that angles up to 120° can be measured. The mirror sextant consists of a fixed horizon mirror and an index mirror, which is mounted in the center of the rotating pointer arm (alidade). For height determination, the mirrored image of the object is aligned with the direct image of the horizon. The necessary displacement of the pointer arm can be read from the measuring scale and corresponds to the height of the object above the horizon. For observing the sun, solar filters can be inserted into the ray paths. In astronomy, a sextant was used, among other things, to measure altitude for subsequent position determination. The Austrian-German astronomer Franz Xaver von Zach (1754-1832), director of the observatory in Gotha, visited Basel in 1805 and determined, among other things, the latitude of Basel with the help of Troughton's sextant.
Object description
Manufacturer: Edward Troughton (1753-1835)
London, around 1800
Brass, engraved, silver (limbus), mirror, with accompanying box made of mahogany wood to store the instrument
Signature: Troughton London
Purchased in 1805 by Daniel Huber, professor of mathematics, from Franz Xaver Freiherr von Zach, director of the observatory in Gotha, Germany
Deposit Astronomisch-Meteorologische Anstalt der Universität Basel, Phys. 6.
Inv. 1960.21.