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Explorer's Alidade

Detailed Description

Manufactured by Keuffel & Esser, New York & New Jersey. In this type of alidade, as opposed to the high standard, the telescope mounted close to the straightedge, producing a more compact instrument. A right-angle prism is attached to the eyepiece and permits viewing by looking down. A cylindrical bubble and magnetic compass needle are attached to the base; these are used to level and orient the plane table to its proper position.
Object ID: USGS-000161

Sources/Usage

Public Domain.

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