VIXEN New Ultra Fast Astrograph VSD 100/f3.8

Ultra Fast Refractor designed  for the Astrophotographer featuring a 5 Elements in 5 Group Lens design. 
This f/3.8 OTA  is Optimized for Digital Imaging

Vixen New VSD Astrophotography Telescope

Vixen NA140SSF
Item #26145

The innovative wide and flat imaging field, that covers 645 medium format cameras, and 5 elements in 5 group lens design completely eliminates a violet tint in chromatic aberration (blue halo). With an SD lens in the front objective group and an ED lens in the rear objective group, this scope achieves superb color correction.  The blue halos around stars, that are visible in astrophotography and are hard to reduce with a 4 elements in 4 group lens design, are corrected successfully.  In addition, astigmatism and coma aberrations are corrected to an extremely high level of image quality.  The VSD 100 comes with an aluminum storage case.

The Strehl intensity on the lens design of the VSD100F3.8 is better than that on a 4 elements in 4 group lens design by approximately 10%.  It does not decrease abruptly on stars away from the center of a photographic field.  It is ideally  suited to detect faint stars.  The image circle is as large as 70mm in diameter (60% illuminated).  The star images are as small as @ 15 microns around the corners, resulting in excellent field flatness. 

The lenses of the  VSD100F3.8 have the most up-to-date coatings of extremely high reflectivity. These have been developed to match the characteristics of each lens element in order to avoid the deterioration of image contrast due to the increase of lens elements.  It boasts of a 99.9% light transmission at the maximum per lens surface and achieves superb images with extremely high contrast with no ghost and no flare images. (Patent pending).

Tony Hallas Says:"To have this level of performance from an f/3.8 is remarkable. All in all..a very impressive little telescope! The telescope is essentially sensational. It accomplishes the impossible. Mechanically superb as well, supporting the heavy 16803 camera without any complaint and the enormous helical focuser is tight and accurate. With extremely fast optics, flat field, and superb color correction it is a unique product not just a rehash of the same. "
VSD Telescope image by Tony Hallas
Image courtesy of Tony Hallas. M42 and The Horsehead Nebula with SBIG STX16803. View Larger Image Here

Vixen VSD Astrograph Telescope Images

  Vixen VSD Telescope cutaway
Precision Glass Annealing Process and a Premium Zygo Verifier ATZ Laser Interferometer. In the process of manufacturing optical glass, all the five lens 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.


Spot Diagram

Center of frame
Edge of full frame 35mm
Edge of a digital 645 format
Edge of full frame 645 format

4 elements in 4 group F3.8 optics (designed for reference)


Vixen VSD Telescope

Describing Lens Performance with MTF Characteristics

Vixen’s goal was to develop a process to outperform the views from a premium photo lens.  The result is the introduction of MTF (Abbreviation of Modulation Transfer Function), previously  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 element 4 group design. Thus, it allows for a more precise evaluation of the photographic performance as compared to conventional spot diagrams.  This is a new direction in the choice of an astrograph.


Spatial frequency
10 lines / mm
30 lines /mm
Distance from center of frame

Vixen VSD Refractor Telescope

Vixen VSC Telescope focuser

Precision Over-sized Focuser and Large Rubber Focus Ring

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 non-rotational helical fine focuser, where the distance 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.

Tony Hallas Image with the VSD 100
Image by Tony Hallas. Viewer Larger Image Here

Optional Focal Reducer and Optional Tele-Extender

A focal reducer (0.79x) with the optical design of 3 elements in 3 groups and a tele-extender (1.58x) with the optical design of 4 elements in 3 groups will be available as optional parts.  With the use of these optional accessories, the VSD100F3.8 can be transformed to an even faster astrograph with 300mm in focal length at F3.0, or can be converted to a more multi use optical tube with 600mm in focal length at F6.0 for observing planets and other celestial objects.

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