Maker

Wild, Heerbrugg (Switzerland)

Model

T4

Serial Number

37448

Dimensions

Telescope Length 540 mm, Height 467 mm

Image

Description

This Wild T4 micrometer theodolite is the largest of the Wild theodolites and is used for angle measurements of the highest accuracy in 1st order triangulation, tunnel set-out, geodetic astronomy and similar precision applications. The theodolite is of the "broken telescope" type, which means that the image formed in the telescope is viewed through an eyepiece placed at one end of the trunnion axis. Its powerful telescope, with approximately 60x magnification, allows comfortable sighting to zenith, because the eyepiece with its 'impersonal micrometer' is always at eye level. Horizontal and vertical circle readings are made with the optical micrometer directly to 0.1" and 0.2" respectively, by coincidence readings of diametrically opposite graduations. It is capable of determining the longitude to 0.01 s, latitude to 0.2" of arc and the azimuth to 0.3" of arc.

The diameter of the objective lens of the telescope is 70 mm, its focal length (f) is 578 mm, and due to its powerful magnification, the shortest sighting distance is approximately 100 m. The diameters of the horizontal and vertical circles are 240 mm and 135 mm respectively. The sensitivity of the altitude bubble for the vertical circle is 2" per 2 mm. The sensitivities of both the hanging level and of the two Horrebow-Talcott levels supplied with the instrument are 1" per 2 mm. 

Tranport Boxes: telescope unit(735x507x300 mm, 21 kg), yoke assembly (534x435x542 mm, 20 kg), hanging level (373x272x117 mm, 7 kg).

The hanging level is marked No. 48 and its vial No. 306. The sensitivity is listed as 1.15"/2mm on a plaque inside the level box.

History & comments

The Wild T4 is world-renowned as the ultimate in theodolites and is undoubtedly the largest among the Wild range. Weighing approximately 60 kg (see above), it is a heavy and solidly built instrument. The telescope assembly has to be removed for transportation.

Conservation

The instrument is presently on loan to Snowy Hydro for display in their exhibit at the Snowy Hydro Visitor Centre in Cooma.

Condition

Fairly good condition

Remarks

• The eyepiece micrometer in the theodolite can be attached directly to a Chronograph during longitude determinations.
• Theodolite donated by the Snowy Mountains Hydro-Electric Authority (S. M. H. E. A.), now 'Snowy Hydro'
• Inscription: 'S. M. H. E. A.'
• Thanks to J. Dedual for the correct year of manufacture
• Catalogued by T. Ko
• Updated by F. Pall & J. M. Rüeger

Dates

Manufactured in 1957. Catalogued in 1997 & 2005.