Goerz rangefinder

 

 

The Goerz rangefinder for field artillery, one meter base consisted of :

1.      the rangefinder proper;

2.      the tripod;

3.      the adjusting bar, used to examine rangefinders as to their exactness in measuring and their adjustment, if required;

4.      the accessories;

5.      a wooden box for storage and transportation of all rangefinder part.

The eye-piece a was adjustable to the eyes of the observer and was equipped with diopter arrangement. The spirit level t serveed for measuring angles of site, which were read from scale drum on the level screw u and the coarse scale on the level carrier.

 

Before beginning to measure, the eye-piece was set for the visual distance of the observer by means of the diopter scale. If the distance be unknown to him, the eye-piece was set by turning until the image of a far distant object with the greatest possible amount of details, such as walls, bushes, frameworks, and the like, appeared absolutely sharply defined. The resulting number of the diopter scale should be memorized. In harsh light or heavy haze in the distance the orange or yellow screen, as required, was to be used on the eye-piece.

The rangefinder having been coarsely set at the target, if necessary by means of the finder, the object was looked for in the field of view. Lateral setting was accomplished by turning the rangefinder on the tripod pivot after loosening the locking lever m. For use against stationary targets that lever was relocked after the rangefinder had been properly set. The adjustment for height was affected by means of adjusting screw s.

 

The rangefinder’s field of view was divided into two parts by a horizontal line. In the lower part of the image of the object appeared upright, and in the upper part inverted. By turning the height adjustment screw s the images were lined up so that the proper points will touch the dividing line. By turning the measuring screw b the image was shifted laterally until the same vertical rim or similar points of the object are laterally exactly above one another. The distance was then read on the distance scale c.

With laterally moving targets, the images should be adjusted on the edge of the field of view corresponding to the direction of the movement and the measurement should be made while the image run through the field.

With targets which had no prominent vertical lines or points, but showed horizontal lines, such as tops of heights or entrenchments, the distance was measured on the horizontal line by setting the instrument vertical. Errors in height of the instrument prejudiced the exactness in measuring, if the line was sighted at did not run exactly horizontal.

 

The rangefinder could not, except in cases of extreme urgency, obviate the necessity for adjustment in range by the observation of fire. The most important use of the rangefinder was in determining the first range that should be used in attacking a target. By its use, the first range would be, on the average, much closer to the target than if this range was an estimated one. This fact permitted the range change used prior to obtaining a bracket to be profitably reduced when the rangefinder was used, saving time and ammunition in adjustment. The rangefinder was a complex and delicate instrument, so great importance was attached to the training of the operators. They should be accurate, rapid, able to recognize a range not reliably found and to promptly inform the battery commander of this fact.

 

SOURCE : “Goerz Artillery Rangefinder, E 115 – One Metre Base”. The Field Artillery Journal, 5/1 (January-March 1915): pp. 164-173.

 

 

 

Technical characteristics

 

Weights

Rangefinder :

8.35 kg

Tripod :

1.9 kg

Adjusting bar :

6.6 kg

Storage box :

28.6 kg

Optical data

Magnifying power :

15x

Actual field of view :

2° 40’

Actual field of view at 100 meters :

46 m

Entrance pupil :

37 mm

Exit pupil :

2.5 mm

Illumination :

6.25 mm

Shortest distance measurable :

600 m

Average errors in setting under favorable conditions

Distance

Error in setting

Distance

Error in setting

600 m

1.2 m

3000 m

29 m

700 m

1.5 m

4000 m

52 m

800 m

2.1 m

5000 m

81 m

900 m

2.6 m

6000 m

116 m

1000 m

3.2 m

7000 m

158 m

1500 m

7.5 m

8000 m

207 m

2000 m

13 m