repeating circle circle of Borda - eighteenth centuryJecker signed in Paris dated 1794. ( workshop Jecker brothers assets from 1793 to 1819 ) , turned ebony handle , telescopic sight , with vernier reading glass , circle 360 silver and 720 parts graduated in its original mahogany box with brass fittings , many accessories , diam. 28 cm bearing No. 268. Quite complete instrument all filter sets for large and small mirror and scope. With riders setting. Removable handle. In his mahogany box Box : 30 x 30 cmBienvenue :) Visitez notre site: http://www.la-timonerie-antiquites.comWELCOME :) .......PLEASE VISIT THE SHOP THANKS http://www.la-timonerie-antiquites.com/en calculating longitude at sea was done in three ways : estimation of the road of the vessel with compass and log (measuring speed ), the average reading time given by a clock; angular distance measuring Moon - Sun or Moon - stars . The latter method is disposed specific instruments only from 1750 , when Mayer offers the reflecting circle . Borda make the instrument more reliable, easier to use and faster.The repeating circle is an instrument for geodetic surveying, invented by Etienne Lenoir in 1784, while an assistant of Jean-Charles de Borda, who later improved the instrument. It was notable as being the equal of the great theodolite created by the renowned instrument maker, Jesse Ramsden. It was used to measure the meridian arc from Dunkirk to Barcelona by Delambre and Méchain.The repeating circle is made of two telescopes mounted on a shared axis with scales to measure the angle between the two. The instrument combines multiple measurements to increase accuracy with the following procedure:
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