Dosenfernrohr Grosses Modell with 12, 25, 40 revolver eyepieces and a 60 mm objective lens, made by Carl Zeiss Jena in 1898.
The name of the model derives from the round, "tin can" type prismatic housing which contains an "Abbe-Amici" roof prism system. Therefore the Dosenfernrohr or Revolver Telescope was the first model produced for the civilian market with a roof prism and very powerful variable magnifications.
The Dosenfernrohr has a variable length from 55 to 59 cm, depending on the choice of the eyepiece and increases by 10 cm when the sunshade tube is extended, which is equipped with an objective lens protection cover.
This large Dosenfernrohr is in excellent condition and all mechanisms work perfectly - the view is bright and clear on all three magnifications.
These telescopes are ideal as tourist and travel telescopes due to their short tube length and low weight. They are delivered in 2 models. In both models, an (Amici-Abbesche) prism system is used to realign the image created by the lens in an inverted position; The much shorter astronomical eyepiece then takes the place of the usual terrestrial eyepiece.
Since the prism system also causes a small shortening of the tube length between the lens and the image plane, the result is an instrument that is unusually short and can therefore be brought particularly easily on its bearing into a suitable position in relation to the observer's eye.
By eliminating the terrestrial eyepiece, it is also possible to give the field of view the extent that can be achieved at the given magnification. The fact that the reverse prism system used is straight-sighted, i.e. the eyepiece is in the axial direction of the tube, is not just an aesthetic advantage, it makes aiming a single telescope noticeably easier.
The three eyepieces corresponding to the three magnifications are mounted on a turret ring that tightly encloses the housing of the prism system. This can-shaped housing is the characteristic part of the instrument for its construction and appearance, which is why we have called it a can telescope. The housings of both models are made of aluminum, the actual tubes are leather-covered.
At the end of the lens there is a sleeve on the tube, which, when pulled outwards, protects the lens from rain and sun and is closed with a lid. This telescope has a lens aperture of 60 mm and a choice of magnification of 12x, 25x and 40x. The instrument rests in a clamp above the vertical and lateral joints.
In order to be able to raise and lower it as a whole, the directional joints sit on a vertical rod, which is moved up or down by turning one of the handwheels in the stand screwed out of the wooden tripod. The instrument and lens cap are housed in a sturdy cowhide leather case with a shoulder strap. The bearing remains on the wooden tripod.