Series of lenses “Rubinar”

Rubinar is a family of mirror-meniscus lenses with a large focal length, manufactured at the Lytkarino Optical Glass Plant (OJSC LZOS). Lenses of this family are intended for use as interchangeable lenses for small format single-lens reflex cameras.

The main application of the lenses of the Rubinar family is astro photography, photographing distant objects, birds and other animals (photography).

Optical design

The desire to increase the focal length of the lenses while maintaining the small dimensions of the frame led to the creation of an original design of the MTO series lenses, consisting of lenses and mirrors deposited on a spherical surface.

Lenses “Rubinar” were created on the basis of photographic lenses “MTO” and ” ZM ” made according to the modified Maksutov  – Cassegrain scheme with a prefocal field corrector.

The Rubinar is a catadioptric telescope according to the scheme most often referred to as the Richter-Slevogt scheme after the names of German opticians. Its other names are “ Volosova – Galpern – Pechatnikova “(USSR), and” Houghton “(USA). The scheme includes a pair of full-aperture lenses, primary and secondary spherical mirrors, and an astigmatism and field curvature corrector, which is a small-diameter negative prefocal lens mounted behind the primary mirror and extends the focal length by about 1.4 times. The secondary mirror is of the mangen type, installed in the front full-aperture lens. The central shielding by the secondary mirror is, in different models, 13-36% of the area, or 34-50% of the entrance pupil diameter. The lens creates a wide, flat photographic field. Can be used as a lens or telescope. Aperture of various models from 53 mm to 106 mm.

Focusing the lens – manual according to the image on the focusing screen. The relative aperture of the diaphragm is constant. Lens mount – threaded М42 × 1 / 45.5 or K bayonet. They have a threaded socket for mounting on a tripod (except Rubinar 4.5 / 300 and Rubinar 8/500).

Use as a telescope

Due to its small size, light weight and robust metal construction, Rubinar is well suited as a portable traveling telescope.

The manufacturer provides for two ways of using the Rubinar lens as a telescopic observation system, both of which give a straight, non-inverted image, like in a telescope, which is very convenient. The first way is to use a commercially available “Tourist-FL” eyepiece; the second is the Astrorubinar set, supplied only with the MC Rubinar 10/1000 macro lens.

In addition to the options provided by the manufacturer, there are many others. The lens can be turned into a telescope using a separate eyepiece and adapter with an M42x1 female thread on one side and an eyepiece seat on the other. At the same time, in order to fully realize the capabilities of Rubinar, you need to use 2 ″ form-factor eyepieces and a corresponding adapter with M42x1 mount.

With the use of the “Tourist-FL” eyepiece, the magnification reaches 111 × (for “Rubinar-10/1000”). With the addition of a two-fold teleconverter, such as the MC K-1, serving as a Barlow lens, the magnification is accordingly doubled to 222 ×.

A more solid and expensive version of the telescope based on the Rubinar lens is called Astrorubinar. In addition to the MC Rubinar 10/1000 macro lens, the Astrorubinar telescope kit includes two eyepiece assemblies: straight and with a 90-degree prism, as well as a set of three 1.25 ″ eyepieces (standard form factor of eyepieces used in telescopes) …

Eyepieces supplied by LZOS (9.4 mm (56 degrees), 15 mm (Plesl, 40 degrees) and 30 mm (Köllner, up to 30 degrees)), together with the “zoom” of the eyepiece units, provide a continuous range of magnifications from 22 up to 175 times (22-54, 44-110, and 70-175). The eyepieces are not supplied with boxes and lids. The prism, in the eyepiece unit – without a cover, with one reflective surface, that is, it gives an incongruent – mirror-inverted image, which is inconvenient for observing terrestrial objects.

The linear light diameter in the eyepieces and eyepiece units (linear field of view) of the Astrorubinar and Tourist-FL is small, about 12 mm. This is less than in prismatic binoculars and spotting scopes, where this parameter is usually about 16 mm, and, moreover, does not correspond (much inferior) to the parameters of the 1.25 ″ form factor eyepieces, which have a light diameter of about 26 mm.

The center of gravity of the “Rubinar-1000” is set forward in relation to the tripod socket by 5 cm, it passes through a wide focusing ring. The set of the Astrorubinar telescope does not include a finder, its mounting on the telescope lens is not provided

Other features

Bokeh

Due to the optical design of the mirrored lens, only a part of the front lens (ring) works in Rubinar, because its central part is obscured by a secondary mirror. Because of this, the energy diagram of the scattering spot has a recession in the center, and, as a consequence, unsharp point light sources will be displayed in the form of rings (“bagels”).

Macro photography

Lenses of the Rubinar family allow macro photography at a scale of up to 1: 4.

Light filters

Lenses “MC Rubinar 10/1000 macro” releases after 2000 were equipped with full-aperture filters M116 × 1.0. The set included three unclarified filters UV-1.4 ×, ZhZ-4 ×, O-8 ×. The multiplicity of filters is increased in comparison with conventional filters of the same colors with a smaller diameter, due to the large size, and, accordingly, the thickness of the glass, and the absorption in it.

The form factor of the M116 × 1.0 filters, having a light diameter of 101 mm, is not suitable for the MC Rubinar 10/1000 macro lens, since it “cuts off” its 106 mm aperture by 5 mm. Filters of this size in Soviet optics were used, except for Rubinar-1000, only in one more lens MTO-11ca (1000/10), of the same plant. In the rest of the lenses with a focal length of 1000 mm, filters with threads M120 × 1.0, 5M120 × 1.0 were used. Thread М116 × 1.0 is not included in the range of standard threads according to GOST 3933-75 (1995). The M120 × 1.0 filter form factor is also small for this lens.

Lenses “MC Rubinar 10/1000 macro” of early releases – until 2000 – instead of full-aperture M116 × 1.0 were equipped with only small M35.5 × 0.5 light filters (light diameter 31mm) of reduced height (low-profile), screwed into the lens from the side mounts to the camera. The set included 5 pieces of UV-1 ×, ZhZ-2 ×, O-2.8 ×, N-2 ×, N-4 ×. Later releases came with full-aperture filters and were not equipped with screw-in М35 × 0.5, but the possibility of their use remained.

Adapters for modern cameras for Rubinar lenses

Installation on modern digital cameras (SLR or mirrorless digital cameras with interchangeable lenses) is possible using the appropriate adapters (for example, M42 × 1 – K-mount or M42 × 1 – NX-mount).

Installation on SLR cameras is often complicated by the presence of a built-in flash that is very prominent in front of them.

By ordering things from the links below, you help the project cover the costs of site maintenance and development. List of adapters, systems and mounts (direct links for ordering)

When ordering, it should be borne in mind that cheap adapters of poor quality with a lens on the Nikon F mount significantly spoil the picture. Adapters without a lens reduce the maximum focusing range (due to the difference in focal lengths). Adapters with chips come across poor quality, exposure metering and focus confirmation on some Canon EOS models may suffer from this.

Options

  • MC Rubinar – 4.5 / 300 Macro
  • MC Rubinar – 5.6 / 500 Macro
  • MC Rubinar – 8/500 Macro
  • MC Rubinar K – 8/500 Macro (mount – K bayonet)
  • MC Rubinar – 10/1000 Macro
  • MC Rubinar K – 10/1000 Macro (mount – K bayonet)
  • Astro Rubinar-100-B (based on MC Rubinar 10/1000)
  • Astro Rubinar-100-S. Does not have a turning system for ground observation. The performance of the main mirror made of sitall and the rigid installation of the lens to “infinity” (no focusing ring) allows to increase the system’s resistance to changing temperatures and achieve better visual quality of the image in the center of the field of view.

Marking “MC” means the presence of multi-coating

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