Accession No
2457
Brief Description
transit theodolite, by Cooke, Troughton and Simms, English, 1943 (c)
Origin
England; York
Maker
Cooke, Troughton and Simms
Class
surveying
Earliest Date
1943
Latest Date
1943
Inscription Date
Material
metal; glass; wood
Dimensions
box length 340mm; breadth 215mm; height 184m; horizontal circle 120m; telescope length 198mm; height 260mm
Special Collection
Provenance
Transferred from Department of Engineering, University of Cambridge, Cambridge, England, 09/1979.
Inscription
‘Cooke Troughton and Simms. York England No 42051 Pat No 471089 Pat No 518148’ (on limb)
Description Notes
Grey finished metal alloy construction. Inverting telescope with internal focus by milled ring around body at eyepiece end. Telescope transits over objective. 2 fitted eyepiece filters. One marked ‘L’ the other ‘D’. Eyepiece focus. Bubble mounted on left of transit axis with double hinged mirror over. Levelled by screw at base of frame. Horizontal and vertical circles completely enclosed; read by micrometer microscopes on either side of the telescope. Left hand reads vertical circle, the right reads the horizontal circle; both to 1” of arc. Hinged mirror on end of left axis reflects light onto scales to facilitate reading. Knurled vertical motion clamp on right hand transit axis; motion screws at base of right hand frame. Clamp and motion screws for horizontal circle and scale on limb. 2 levelling bubbles mounted on limb.
3 levelling screws clamped to a base; threaded hole for attachment to tripod head. Plumb-bob. Lens cover. Torch unit. Attachment for fitting to left hand axis to illuminate scales. Ray shade. Fitted wooden box.
References
Events
Description
The Theodolite is a relatively, simple tool used for measuring angles, both horizontal and vertical. They work using the same principles as a protractor, the ‘point A’ is located and the angle noted, and then the telescope is pointed at ‘point B’ and the second angle is taken.
Although primarily used in surveying the theodolite can be applied to both Meteorology and Navigation.
Gemma Frisius proposed the idea behind the theodolite in 1533. At the time new methods of surveying were being used and by combining an Alidade, a magnetic compass and the degree scale on the back of an Astrolabe, the calculations made by modern theodolites could be observed. Unfortunately, this method was not practical due to the combination of instruments. The best of the attempts to simplify the process was the ‘theodolitus’, first described in print by Leonard Digges in 1571.
However, this instrument could only take measurements in the horizontal plane. Despite this it was still thought of as the ‘common’ Theodolite up to the late 18th century.
During the 19th century the Altazimuth Theodolite was considered the most useful theodolite, as it could measure on the horizontal and vertical planes. Three notable types of Altazimuth Theodolite were developed: The Everest Theodolite, the Plain Theodolite and the Transit Theodolite. It is the Transit Theodolite, which is still used today.
FM:42883
Images (Click to view full size):
