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Optics In all our refractors we use the highest quality optical sets available on the market. We�re currently using one of the best 80 mm optic on the market, the Super APO triplet F/6 produced by LOMO and the full APO triplet line, from 105 to over 200 mm diameter, designed by Thomas Back and produced at LZOS factory. Some special products are using other APO triplet objectives developed by our optical designers and produced with the highest quality standards. All LZOS triplet instruments come equipped, as standard, with an interferometric test report. All instruments are tested, verified and collimated before delivery on our autocollimation (double light passage type) optical bench with an artificial laser star at very high magnification. The LZOS factory, with its huge structure placed Near Moscow, is a recognized reference point for the manufacture of research instrumentation in the astronomy field and, thanks to the absolute high quality, especially in the professional one. Its productive capacities allow to produce monolithic mirrors up to various meters of diameter, and the company is among the very few capable of producing special raw materials for astronomy. Besides the life long experience of the technicians and the very modern equipment used, one of the most important strong points on refracting optics manufacturing, is the internal production of all glasses and optic materials necessary for the production of the finished objectives. This allows to control the true characteristics of light dispersion of the single glass casting and the attainment, during the manufacturing of the surfaces and their assembly, of the highest expectations in performance. Every objective produced is mounted, aligned and tested before delivery to Officina Stellare directly in LZOS. Our task, thanks to our careful mechanics design and final assembly, is to guarantee the attainment of the max imum theoretical possible performances of the objective. With the help of the page �Essay on Optics� written by Thomas Back on his web site, we want to help the customer to have a sharp idea of some definitions widely used on the apochromat refractormarket. In this text which we report below there are also some important infos on the material used for the LZOS objectives and on their performances. �Apochromatism�: an old definition With the proliferation of apochromatic refractors that are available to the amateur astronomer, it is time to define the parameters of a true apochromaticobjective lens. The modern definition of "apochromat" is the following: an objective in which the wave aberrations do not exceed 1/4 wave optical path difference (OPD) in the spectral range from C (6563A - red) to F (4861A - blue), while the g wavelength (4358A - violet) is 1/2 wave OPD or better, has three widely spaced zero color crossings and is corrected for coma. �Apochromatism�: a brief history Abbe, working for carl Zeiss during the last years of 1800, discovered that by using optically clear, polished natural fluorite, in a microscope objective, the �apochromatism� could be achieved. These first true apochromatic microscope objectives were so superior to the competition, that Zeiss gained nearly the entire high end market. So secret was the use of fluorite, that Abbe marked an "X" on the data sheet for the fluorite element, so as to keep it secret from the other optical companies. Abbe's definition of apochromatism was the following. Apochromat: an objective corrected parfocally for three widely spaced wavelengths and corrected for spherical aberration and coma for two widely separated wavelengths. This definition is not as simple as it sounds. Abbe's definition, to put it in clearer terms (I hope) is that a true apochromat is an objective that has three color crossings that are spaced far apart in the visual spectrum (~4000A, deep violet to ~7000A, deep red). But what about the levels of spherical aberration at each of these wavelengths? Abbe, in his definition of apochromat, states that spherical aberration must be corrected for two widely spaced wavelengths. �Apochromatism�: searching for a definitive defintion T.B. explain us what happens whenwe try to correct spherical for two widely spaced wavelengths: we correct for all the wavelengths between them too. This is called correcting for spherochromatism (the variation of spherical aberrationwith a change in wavelength). Obtaining this is not so simple. We need to do a combination of a lot designs/factors. It is the designer that must come up with a good compromise of color correction, lack of spherical aberration (3rd order and zonal) and controlling spherochromatism, so as not to degrade the image contrast. All major brands use different technics: wide air-spaced Petzval design, Fluorite and/or exotic glass, large air spacing, slightly aspherization, etc. to control the above aberrations. T.M. designed LZOS objectives optical uses Russian OK-4 super ED glass with an outer crown and a special dense crown glass, using air spacing with different internal radii, and hand figuring to control these aberrations. Now you might ask, after all this, just what is a modern definition of apochromatism? Well, as you read, it is not only three color crossings. One of the first things an optical designer discovers is that with catalog glass data, it is easy to design lenses with three or even four color crossings (superachromat). But what is really important is how small the chromatic focal shift is (not the zero crossings) over a wide spectral range, and how low the spherical aberration is over that same range. So we are left with an ambiguous definition. After designing, testing and selling many different apochromatic lenses T.M. remember us that there is no "definite" line where a lens becomes "apochromatic" in the world of commercial apochromatic lenses. A modern definition for "apochromatic" is not so simple to write. No matter the kind of optical scheme we are talking about (doublet, triplet, quad, air-spaced or Petzval).We need to talk about Strehl ratio, coma correction, wavelength of diffraction limited color correction, spherical aberration, good control of the violet g wavelength and optical spot sizes that concentrate the max imum amount of photons within the diffraction limit. We need to talk about all this to satisfy amodern definition of "Apochromatism." Materials All our refractor OTAs are made of aluminium (6061 anticorodal � 7075 ergal) for the rear and front assembly (fully CNC machined) and true carbon-graphite fiber for the tube (high module true carbon-graphite fiber, obtained in high vacuum chamber). Each OTA is machined to the highest tolerances and is computer optimized to be lightweight with the best structural rigidity. The internal baffles (we use up to 7 internal baffles for the tube, from the lens to very close to the focuser and others directly inside the focuser) are laser cut from stainless steel and glued to the tube with a professional glue. The true carbon-graphite fiber allows to obtain a very stable focus position at very large temperature variations and is very Serie Hiper APO brochure. v.01/2010 lightweight, really useful for great diameter refractors. Design In our OTAs we use the original lens cell provided by the optics manufacturer, the installation is carried out very carefully and particular attention is used to avoid introducing any mechanical stress on the lenses. Our dew and light shield is fully retractable to make the tube size very compact for transport. We put a lot of attention in all our design to prevent any internal reflection (using very opaque paint, even on all the laser cut internal baffles, and black velvet on all other parts) and scattered light. This allows to obtain the max imum performances of the optics. Some innovatons In all our 130 mm and larger refractors, we are proud to announce a very innovative solution for the problem relatedwith the residual internal heat. This is the Officina Stellare exclusive Cooling & Internal Seeing Stabilization System. This system consists of: -9 little holes, drop shaped, CNC machined on the conical section of frontal aluminium assembly (dew shield support). -9 little holes, drop shaped, CNC machined on the conical section of rear aluminium assembly (focuser support). -3 internal electrical microfans,with hand speed control All internal baffles are redesigned and laser cut to convey the air flux along the internal walls of the carbon-graphite tube, without the danger of getting dust inside the tube. Thanks to this solution, large refractors (this feature is standard
This product was added to our catalog on Sunday 18 July, 2010.
Since 4 August 2006