0228
   OPTICAL SCALE-READING THEODOLITE  
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  Surveying Instrument Collection 

Maker

Carl Zeiss, Oberkochen, Germany

Model

Th 4

Serial Number

63707

Dimensions

Telescope length 150 mm, Height 270 mm

Image

Zeiss Th 4 Optical Scale-Reading Theodolite

Description

This Zeiss Th 4 optical scale-reading theodolite of medium accuracy was developed as a modern instrument with a reading microscope for the multitude of applications requiring setting-out, alignment, measuring of vertical and horizontal angles or distance stadia measurement. It is therefore suited for building-site surveys, lot surveys in cadastral and urban surveying, low-order triangulation, ground-control work, trigonometric levelling, topographical tacheometry and traverse surveys for cadastre, reallotment and mining. 

This instrument, as with the Zeiss Th 2, features the "ball-and-socket" levelling system. Some other features of the theodolite include: optical plummet built into the alidade, combined coarse-fine focusing drives, automatic vertical circle indexing system featuring a V-type compensator, inverted telescope image and a sighting collimator for rapid and convenient coarse pointing. 

The simultaneous viewing of the horizontal and vertical circles eliminates the need for changing over between readings. Also, the graduation images of the horizontal and vertical circles are colour coded for easy differentiation (blue for vertical and yellow for horizontal).

The graduation interval of the horizontal and vertical circles is 1 degree, the optical scale interval is 1 minute (1') and estimation can be made to 6". The diameters of the horizontal and vertical circles are 98 mm and 85 mm respectively. The sensitivity of the plate level is 30" per 2 mm and the setting accuracy of the compensator is approximately 1". The magnification of the telescope is 25x, the diameter of the objective lens of the telescope is 35 mm, and the shortest pointing distance is approximately 1.2 m.

The instrument's plastic case is fitted with a number of accessories including a plumb bob and a cylinder telescopic attachment for glare reduction.

The "ball-and-socket" levelling system is also incorporated in the Zeiss Th 2 theodolite (Cat. No. 0227 in collection). The weights of instrument and container are 4.5 kg and 3.0 kg respectively. Inverted telescope image.

Includes Zeiss S22 wooden telescopic tripod (150 x 150 x 1150 mm when folded).

History & comments

The standard deviation of a direction measured on both faces is quoted as 3".

Conservation

Plastic container

Condition

excellent

Remarks

 

Donated by Mr. Lothar Bulla (formerly with Carl Zeiss Aust P/L) in June 2004. Instrument S/N 80883 is shown on photo.

Dates

Catalogued in 2004.

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