Brass framed reflecting circle with case.

Reflecting circle made by Charles West, London, 1817-1822. Circular lacquered brass frame and index arm, polished limb, two detachable wooden handles. Signed on the limb: C. West, 5. Cursitor St. Chancery Lane, London. Inlaid silver scale from 0° to 180° (four times) every 20'. Three silver verniers to 10", zeros at the right. The index arm carries the index glass; the telescope arm carries the horizon glass. The tangent screw and clamping screw are on the back of the index arm; two clamping crews are at both ends of the telescope arm. Four index shades (two red, one green); three horizon shades (two red, one green). Index-glass adjustment by screw; adjustment of the horizon glass by screw and capstan screws. Detachable magnifier serving two verniers on a 40 mm swivelling arm; a second, fixed magnifier is on a 25 mm swivelling arm. Threaded telescope bracket in two parts, fitted for correcting collimation error; perpendicular adjustment by rising-piece and a milled collar. Telescope (84 mm) erect image; telescope (152 mm) inverted image, four cross-wires; extra draw tube (57 mm). Sight tube (83 mm); shaded eyepiece (red); adjusting key; adjusting pin. Square fitted mahogany box containing in the lid a broadside of James Allan at no. 12 Blenvitts Buildings, Fetter Lane, London, announcing his new, improved, self-correcting dividing engine, and the prizes he received for this. The broadside was printed after 1811.

Details

Category:
Astronomy
Object Number:
1981-694
Materials:
brass, glass, wood and silver
type:
reflecting circle and instrument case
credit:
Delehar, P.

Parts

Brass framed reflecting circle.

Brass framed reflecting circle.

Reflecting circle divided by James Allan and Signed by C. West.

Object Number:
1981-694/1
type:
reflecting circle
Image ©
The Board of Trustees of the Science Museum
Case for reflecting circle.

Case for reflecting circle.

Fitted box with accesories, bearing Allan's trade label, for reflecting circle divided by James Allan and Signed by C. West.

Object Number:
1981-694/2
type:
instrument case
Image ©
The Board of Trustees of the Science Museum