Octant
The octant (from Latin octans , the divided arc of a 45 degree segment of a circle , i.e. the eighth part [of a circle]) is a nautical device for measuring angles . Its name refers to the circumference of the attached scale of 45 ° (one eighth of a circle). Because of the reflection in the beam path, the measurement range is twice as much (namely 90 °). The scale is divided accordingly.
It was developed by the English astronomer and mathematician John Hadley together with his brothers George (1685–1768) and Henry (* 1687) and presented to the Royal Society in London in 1731 . First referred to as the Hadley Quadrant , it became the forerunner of the more modern sextants . The originally around 50 cm large wooden instruments could be reduced to a more manageable size by using brass .
Also in 1731, Thomas Godfrey developed an octant in the American colonies .
Since the octant can only measure angles of up to 90 ° - that is, it was only of limited use when determining length using the so-called lunar distances - it was replaced by the sextant in the late 18th and early 19th centuries.
See also
literature
- Dreier, Franz A .: angle measuring instruments. From the 16th to the 19th century , Kunstgewerbemuseum, Berlin, 1989
- Randier, Jean: Nautical Instruments . Stalling, Oldenburg, 1979, ISBN 3-7979-1895-X
- Mörzer, Bruyns Willem FJ: Schip right door Zee. De Octant in de Republiek in de achttiende eeuw. Amsterdam 2003
Individual evidence
- ^ Karl Ernst Georges : Comprehensive Latin-German concise dictionary . 8th, improved and increased edition. Hahnsche Buchhandlung, Hannover 1918 ( zeno.org [accessed on March 13, 2019]).
- ^ Benjamin Franklin: The Autobiography of Benjamin Franklin . Dover Publications, Mineola 1996, ISBN 978-0-486-29073-7 , pp. 45 (American English, limited preview in Google Book Search).
