Reflecting circle made by Edward Troughton, London, about 1823. Signed on the index arm: Troughton | 219 | London. Polished brass limb with inlaid silver scale from 140° to 0° to 140°; the entire circle is divided every 20'. Three silver verniers reading to 20", zeros at the left. Circular lacquered brass frame with a wooden handle. A detached U-shaped bracket holds a second handle with a brass-lined threaded hole for a third handle, which can also be screwed on the front of the frame. Three rigidly connected index arms on the back of the frame, a double-ended tangent screw and clamping screw are on the back of one of the arms. Three shades (two red, one green); three horizon shades ( two red, one green). Index glass without adjustment; adjustment of the horizon glass by a screw and a capstan screw. One detached magnifier on a 55 mm swivelling arm, for all three verniers. Threaded telescope bracket in two parts, fitted for correcting collimation error; perpendicular adjustment by rising-piece and a milled collar. Telescope (77 mm) erect image; telescope (179 mm) inverted image two parallel cross-wires; extra draw tube (90 mm) inverted image; extra draw tube (90 mm) inverted image, two parallel cross-wires. Sight tube (132 mm); sight tube (131 mm, probably from a different instrument); three shaded eyepieces (one red, two orange); a magnifying glass. Three unidentified parts. Box not seen WMB. The circle is mounted on a lacquered brass column on a tripod stand with three milled levelling screws. The counterbalanced swinging mount can be locked into the desired position by milled screws.
One of two cases for reflecting circle, 10 inch, on stand, by Troughton, reads by vernier to 10 secs of arc.
One of two cases for reflecting circle, 10 inch, on stand, by Troughton, reads by vernier to 10 secs of arc.
Reflecting circle, 10 inch, on stand, by Troughton, reads by vernier to 10 secs of arc.
