Wild t4 theodolite
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 metres. 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.
The circles are to the best of my recall graduated to 4' of arc
The Wild T4 is world-renowned as the ultimate in theodolites and is undoubtedly the largest among the Wild range. Weighing approximately 60 kg, it is also a fairly heavy and solidly built instrument. The telescope assembly has to be removed for transportation. There are separate cases for the alidade, telescope & suspension level.
Radio receiver for time signals
The RCA AR88 is a superhet 20 valve receiver, the one used had an extra circuit fitted in order to activate the Mercer chronograph.
Time signals mainly used were from MSF at Rugby. but on
occasion we used WWV and others
|Chronometer and Chronograph
|A Mercer ½ second
chronometer was used in conjunction with a mercer tape chronograph
The chronograph was modified to use side moving pens instead of the normal needles because the signal from the radio was not sufficient to pierce the tape.
Signal from the impersonal micrometer on the T4 came to the chronograph by wire.
|The timekeeping equipment was housed in a Morris
Commercial 2*4 office vehicle and power came from a petrol
driven generator on a trailer
shown below is a similar vehicle in a different livery
A Morris Commercial Office vehicle 4*2
Thank you to Richard for permission to use this
Initial calculations were performed using
"Apparent Places of Fundamental Stars."
Star almanac for Land Surveyors
Peters 8 figure table of natural trigonometric functions
calculating machines used included
Brunsviga double bank machine
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