The VSD100F3.8 astrograph features a wide photographic field of view. The image circle is as large as 70mm in diameter (60% illuminated at the edge). The star images are as small as 15 microns around the corners, resulting in excellent field flatness. New coatings developed to meet the characteristics of each lens element achieve 99.9% light transmission per lens surface and offer extremely high contrast images without ghost and without flare.
The VSD100F3.8 features a surprisingly fast-f-ratio of F3.8 which is the fastest in this class of quality refractors. The wide and flat imaging field that covers 645 medium format cameras and an innovative 5 elements in 5 group lens design completely eliminates a violet tint (blue halo) in chromatic aberration. It employs an SD lens in the front objective group and another SD lens in the rear objective group to achieve a superb color correction. In addition, astigmatism and coma aberrations are corrected to an extremely high level of image quality. The Strehl intensity on the lens design of the VSD100F3.8 becomes about 10% better than that on a 4 elements in 4 group lens design. It is greatly suited to detect faint light from stars. The star images are as sharp as 15 microns endge to edge with image circle of 70mm in diameter (60% illuminated). The lens coatings applied to each surface achieve 99.9% light transmission at the maximum and deliver superb images with extremely high contrast with no ghost and no flare images.
Vixen has initiated a new project in each stage of their manufacturing process to ensure that better quality is realized in the high performance as designed. In the process of manufacturing optical glass, all the five elements are annealed with a precision annealing process. (The annealing can straighten molecular arrangements of lens elements and thus unify the characteristic of optical glass.) The homogeneity of refractivity in optical glass is enhanced to the highest degree. In addition, Vixen introduced a premium Zygo Verifire ATZ laser interferometer for accurate measurement of optical components. The Zygo Verifire ATZ has a 1000×1000 pixel digital camera for high resolution metrogy that ca never realized previously.n accurately identify sudden changes of a form on the optical surface of lenses. Any irregularities on the lenses can be inspected individually. This provides an in-depth control of the lens quality which was never realized previously. The installation of the Zygo Verifire ATZ is unique at Vixen. It is placed in a vertical position* together with a vibration isolation table to allow for measuring large aperture lenses like astronomical telescopes without stress. *Generrally the laser interferometers are laid in the horizontal position. Because the large aperture lens can distort due to its weight, the vertical placement is employed to avoid this interference.
Vixen's goal was to develop a process to outperform the views from a premium photo lens. The result is the introduction of MTF (abbrevation of modulation transfer function.), typically used for evaluating the optical performance of camera lenses. The diagram clearly describes the optical performance of the VSD100F3.8 as compared to a 4 elements in 4 group design.
The VSD100F3.8 has an oversized focuser that can be attached to the 645 medium format cameras without difficulty. Highly accurate focusing is possible with the precision helical fine focuser, where the travel of drawing in and out the focuser can be read as small as 20 microns with the provided vernier scale. All the graduations are engraved. The grooved large rubber focusing ring can be held easily even when wearing gloves and it is turned smoothly with a large ccd camera attached. The thick front rubber ring on on the top of the dew shield protects the optics by absrobing shock. The length of the dew shield, the position of the inner baffles and their proportions to the diameter of the optical tube have been designed to eliminate ghost in the lens design process and to successfully prevent stray light and flare imanges.
A focal reducer (0.79×)with the optical design of 3 elements in 3 group is available as optional. With the use of the focal reducer, the VSD100F3.8 is transformed to an even faster astrograph with 300mm in focal length at F3.0.
Optical Tube Assembly