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Brass reflecting circle.

1865-1871

Brass scale and protractor by Pistor and Martins

1860-1900
Reflecting half-circle made by Pistor and Martins, Berlin, Germany, about 1860. Brown and yellow-lacquered brass frame, polished limb, a wooden handle. Signed on the limb: PISTOR & MARTINS BERLIN. Marked on the limb: 664. Inlaid silver scale indicating from 350° to 0° to 130° and from 180° to 250°; the entire scale is divided every 10', measuring to 238°. Silver vernier to 10", zero at the centre. The tangent screw and clamping screw (both incomplete) are at the bottom of the index arm. Four half-glass shades (two red, two green), no horizon shades. Index glass without adjustment; adjustment of the horizon prism by capstan screws. Magnifier on a 130-mm swivelling arm, a frosted glass shade. Threaded telescope bracket in two parts, fitted for correcting collimation error by capstan screws; perpendicular adjustment by rising-piece and a milled knob. Telescope (183 mm) inverted image, two cross-wires (broken); telescope (85 mm) erect image; extra draw tube (133 mm) inverted image, two parallel cross-wires. Shaded eyepiece (red). A fitted rectangular mahogany box containing in the lid a trade label for Elliot Brothers, 449 Strand, London (18..-18-..)

Prismatic reflecting half-circle and case

1855-1865