Borda type repeating circle with case.

Made:
1775-1785 in Paris
maker:
Etienne Lenoir
inventor:
Jean Charles de Borda

Repeating circle (Borda circle) made by Etienne Lenoir, Paris, France, about 1780. Circular polished brass frame, limb and fittings, a wooden handle. Signed on one of the struts: Lenoir AParis no. 53. Brass scale from 0° to 720° every 20'. Two brass verniers to 1', zeros at the right. The index arm carries the index glass; the telescope arm carries the horizon glass. The tangent screw is on the front of the index arm; the clamping screw is on the back. A second tangent screw and clamping screw are on the back of the telescope arm, at the objective end. Three detached index shades (all red); two detached horizon shades (red and green), all the shades are secured by thumb screws. Magnifier on a 60 mm swivelling arm. Index- and horizon-glass adjustment by square-headed screws and a detached key. Two bubble levels are fixed at a right angle on the front of the telescope arm. Telescope (170 mm), inverted image, two parallel cross-wires, is fixed on two telescope brackets, with perpendicular adjustment on both by rising-pieces and milled knobs. A round plane mirror (probably not original to this instrument), a diaphragm, an adjusting key, and a screwdriver. A square, fitted oak box with the remains of a leather carrying handle.

Details

Category:
Astronomy
Object Number:
1910-128
type:
repeating circle and instrument case
credit:
J.C. Stevens Auction House