A quadrant (from Latin quadrans 'the fourth part' ) is a historical astronomical instrument with which the elevation angles and positions of stars were determined.
Layout and function
The classic quadrant consists of a quarter circle with graduation , a corresponding reading device, a visor and a plumb bob . The star to be measured was sighted using the rear sight and the front sight . The position of the hanging plumb bob on the quarter circle indicates the elevation angle .
Small quadrants were held in hand, larger ones set up on tripods . From around 1650, Adrien Auzout and Jean Picard in particular replaced the visor with a measuring telescope with a micrometer .
Quadrants have been used in astronomy , navigation , geodesy, and topography .
Replica quadrants and modern kits are still in use today, e.g. B. for amateur astronomers , for introductory measuring exercises and - in a further developed form - for determining heights in forestry and construction.
Claudius Ptolemy with quadrant
In addition to the transportable quadrants, large devices were also installed on a wall running north-south, exactly vertical, the so-called wall quadrants , with which a higher measurement accuracy was achieved when observing stars on the meridian . For example, the Danish astronomer Tycho Brahe used the Tychonic Wall Quadrant named after him in his Uranienborg observatory , with a quarter circle of two meters radius. When telescope equipment became standard at the end of the 17th century , large wall quadrants developed into the main instrument of many observatories.
- Sebastian Münster: Rudimenta Mathematica . H. Petri (Basileae), Basel 1551 ( full text in the Google book search).
- Jean Picard: Mesure de la Terre . Imprimerie royale, Paris ( full text in the Google book search). Edited posthumously by Philippe de La Hire around 1685, in which Picard describes in detail his quadrant ( quart de cercle ) in Mesure de la Terre, Article V p. 11.
- John Davis: The Zutphen Quadrant - A very early equal-hour instrument excavated in The Netherlands. In: British Sundial Society Bulletin. Volume 26 (i), March 2014. (flowton-dials.co.uk)
- B. Fermin, D. Kastelein: Het Zutphense Kwadrant. Archeological onderzoek in de gracht van de ringwalburg op de Houtmarkt te Zutphen. (= Zutphense Archeological Publicaties. 80). Gemeente Zutphen, 2013, ISBN 978-90-77587-92-8 . (Dutch)
- ^ Karl Ernst Georges : Comprehensive Latin-German concise dictionary . 8th, improved and increased edition. Hahnsche Buchhandlung, Hannover 1918 ( zeno.org [accessed on March 13, 2019]).