Precision Theodolite (after Gigas) Type Tpr with photographic recording of circle and level readings, manufactured by Askania-Werke of Berlin-Mariendorf, Germany, specifically built for the Soviet Union. The Precision Theodolite comes with a photographic recording camera designed to record time and circle readings. This rare early model was likewise also used by the United States, and was typically grouped with two or three others for advanced missile and satellite tracking; operators used angle measurements from several locations to precisely track the exact position of the missile. The instruments were also capable of surveying their own positions from known reference points or celestial bodies.
Instrument features include a telescope (a magnification of 40 x, 63 x, and 80 x; a field of view at a distance of 1,000 feet of 20 ft., 13 ft., and 8 ft.; a free aperture of objective of 63 mm; and a shortest focusing distance of 33 ft), glass circles (a horizontal circle of 200 mm diameter; a vertical circle of 140 mm; a graduation interval of 4´; and a direct reading to 0,2″), levels (a plate level of 2″/2 mm; and a control level of 5″/2 mm) and photographic recording (a picture size of 24 x 24 mm on standard 35 mm film; camera with spring driven mechanism for about 50 pictures). The main instrument box, with original Askania TPR label, measures approximately 19.25″ x 17.25″ x 17.5″, and weighs 113.5 pounds. The additional cases containing cables, electronics, camera, instrument optical micrometer, and the film optical micrometer measure 20″ x 15.5″ x 7″ and 16.5″ x 15.25″ x 6.5″, and weigh 37.8 pounds and 32.2 pounds.
The Tpr offered includes several options that were used for very high precision observations for determination of the position of the instrument on earth by sighting on stars and using a precision time source. This amounts to a very precise version of celestial navigation as practiced with a sextant, chronometer, and tables of star positions with time. Two additional levels are included—a striding level to set the horizontal axis more precisely than is possible with the level built into the instrument, and a set of two levels known as Horrebow (or Horrebow-Talcott) levels. The latter are used for precise determination of the tilt axis of the telescope. A third optional accessory included is a micrometer eyepiece. This has a reticle used to determine fine star positions with time. The knob moves the reticle and simultaneously sends a signal to a recording chronometer. The recording chronometer (not included with this item) records the precise time a celestial body crossed the reticle lines. If satellites were observed, slight variations in their orbits compared with computed positions could be used to determine variations in the strength of the earth’s gravitational field, very likely a use of this instrument. A copy of the book, “Introduction to Satellite Geodesy” by Ivan Mueller, will be included with the item.
The Precision Theodolite Tpr belongs to the class of universal instruments, and is suited for first order triangulation, flare triangulation, and for astronomical work at Laplace stations. It is designed to read horizontal and vertical angles directly to 0.2″, and to accurately observe the passage of stars. The instrument greatly relieves the observer of routine manipulations and allows them to concentrate upon pointings at the targets. Readings of circles and plate level is performed by the photographic recorder upon pressing a single button, and is done so quickly that the next recording could be achieved one fifth of a second later. A tremendous piece of early technology, and an impressive forerunner to the modern astronomical theodolite.
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