Binoculars Carl Zeiss Jena D.F.8x24

   In 1907, Carl Zeiss radically changed the framework and the design of his binoculars, replacing "civilian" models Feldstecher 6 Fach by Telex, Feldstecher 8 Fach by Telact, Jagdglas by Silvamar and Feldstecher 12 Fach by Telefort. The new devices’ detailed characteristics were published in the 74-th volume of Carl Zeiss catalog in August 1907. The optical characteristics were significantly improved in new devices (the field of view and the objective diameter were increased, optical aberrations were decreased), and the devices’ design was also changed: the central hinge and the “lugs” for a neck strap were not attached to binocular with the help of screws any more, they became integral with it instead, an eccentric objective alignment system appeared and its frame design was also changed, the prism covers spanned the binoculars’ carcass, and they were lubricated with a special compound at the joint points in order to improve impermeability. Moreover, the prisms inside the binoculars were no longer pressed by prism covers – they were fixed with the help of special flat springs instead. It helped increasing the device’s reliability greatly. Actually, the binoculars have survived in such appearance up to present days (see Hans T.Seeger. Zeiss-Feldstecher, Handfernglaser von 1894-1919, Modelle-Merkmale-Mythos, pp.399-414)
   Earlier, around the end of 1906, first military versions of D.F. 8x binoculars appeared in the new design (an old version is available by the following link - https://binocollection.com/catalog/-binoculars-carl-zeiss-jena-df8x.html). These were the analogs of the “civil” Telact 8x model that appeared a little bit later (https://binocollection.com/catalog/binoculars-carl-zeiss-jena-telact-8x.html). The earliest D.F. 8x devices had their own individual number and they were intended for sale to military people in private order with the permission of military department (for example, the D.F. 6x binocular has the same number - https://binocollection.com/catalog/binoculars-carl-zeiss-jena-df6x-1.html. This model was produced with such marking for a very short time. Later, the serial numbers were shifted to the lower right prism cover edge and they started to put military approval number on the upper right prism cover (under the name of the model).
   In 1912-1913, the D.F. 8x binocular in the Telact 8x design was replaced by lighter and smaller (which was very important for military use) model D.F. 8x in the Turact 8x    https://binocollection.com/catalog/binoculars-carl-zeiss-jena-turact-8x.html. For some time both models were produced in parallel, so you can find the second type of binoculars with an earlier serial number compared to D.F. 8x/Telact 8x.
    The D.F. 8x model in the Telact 8x design was replaced by the D.F. 8x model in the Turact 8x design in 1912-1913. This binocular has a little bit smaller field of view (6.3° versus 6.6°) and slightly worse optical features. However, it is lighter and smaller in size (which is important for military use), as well as more technological (and therefore cheaper) in production. Both models were produced in parallel for some time, so one can find the second type of binoculars with earlier serial numbers in comparison with D.F. 8x/Telact 8x model.
   The D.F. 8x24 has 8x magnification and 24mm lenses. The binocular’s “military” application is proved by the central hinge fixture’s (clamp’s) large diameter. The interpupillary distances scale is indicated on the upper hinge disk. The D.F. 8x24 binocular in the Turact 8x design was produced in 2 versions with various design changes until the mid of 1920s:
    1st version: with the double ring-type lens frames (starting from 1912-13 and up to 1914);
    2nd version: with rounded objective covers in two variations: with grooves on the objective covers to minimize stray light and without them (starting from 1914 and up to the mid of 1920s)
   This device belongs to the second, most popular version, with rounded objective covers and without grooves, intended to minimize stray light. The front and rear prismatic covers are made of zinc alloy and they are attached to the binocular with the help of one screw (the covers were fastened with the help of three screws in a previous version). The upper prism cover width is equal to 46 mm; the binocular’s body height (including the upper prism cover) is equal to 69.5 mm. The eyepieces’ base diameter is equal to 20.5 mm and they have the diagonal knurling on the surface (located at an angle 45 degrees). The eyepiece’s front lens design has been slightly modified compared to a previous version of this model (see photo).

   There are inscriptions “Carl Zeiss Jena” on the left prism cover. There is also an inscription “Dienstglas D.F. 8x24 640814 X 1917” on the right prism cover. "Dienstglas" (service glass) is another sign of the binocular “military” application, "X 1917" is probably the date of the device’s manufacture (it quite corresponds to the serial number 832911). The device was manufactured as a large 2000 pieces batch. Unlike previous models, the inscriptions are made in block letters against the background of Carl Zeiss Tessar photo lens schematic image without silver alloy application. The goniometric grid is mounted in the right eyepiece (see photo).
   The previous version of this model can be checked by the following link:https://binocollection.com/catalog/binocular-carl-zeiss-jena-df8x-5.html