Wild T3
The Wild T3 from the Swiss company Wild-Heerbrugg is a precision theodolite for triangulations and was in use until around 1980. It is twice as precise as the widespread second theodolite Wild T2 and, at just under 10 kg, only around 50% heavier. It was developed around the 1930s and essentially goes back to Heinrich Wild , the inventor and company founder of the Wild company.
The T3 achieved an accuracy of at least 0.5 ″ and, thanks to its largely closed design and high stability, surpassed most of the triangulation theodolites used up to that time , whose precision mechanics and pitch circles were open. The name T3 should signal the higher accuracy compared to the somewhat simpler Wild T2 .
The basic concept of the theodolite comes from Heinrich Wild and has proven itself over several decades until the predecessor of today's total stations was developed around 1980. Its height is about 30 cm, its mass just under 10 kg. The achromatic telescope has about 40x magnification and an aperture of 5 cm, internal focusing and lighting. Directly next to the eyepiece of the measuring telescope is a second view for circular reading. It is carried out with short microscopes that mirror two opposite points of the pitch circles together in order to eliminate any eccentricity . The circular reading on the tick marks running against each other corresponds to that of the T2, but, unlike this, was not partially digitized in the 1970s because the series was too small.
The coarse and fine movements for direction and elevation angles are arranged with four rotary knobs on the alidade and the telescope supports. The substructure has an optical plumb line , lighting connections and the horizontal circle adjustment. The vertical axis is cylindrical, which is very robust, but brings with it minor secondary axis errors ("wobble") of up to about 1 ″. Today, combinations of cylinder axes with a horizontal ball bearing are common.
With a number of additional instruments, the T3 has been equipped for demanding special tasks over the years, including a. for marrow separation (special lighting, zenith prism, etc.), for optical distance measurement and even for astrogeodesy - u. a. by a precise Reiter bubble and by the Prismenastrolab -Vorsatz in connection with a specular mercury horizon .