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Vixen Optics VSD100 100mm f/3.8 Astrograph Refractor (ITEM #26145)
Vixen Optics VSD100 100mm f/3.8 Astrograph Refractor (ITEM #26145)

Vixen Optics VSD100 100mm f/3.8 Astrograph Refractor (ITEM #26145)

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Your Price: CAD7,986.31
Retail Price:CAD8,526.96

Your Savings:CAD540.65(6%)

Generally Ships in 5-7 Business Days
Part Number:26145

Choose Options or Accessories if Applicable

Finders and Brackets
Ships Worldwide - This item qualifies for international shipping. help
Focal Reducers/Coma Correctors
Eyepiece Adapters
Imaging Accessories
Product Highlights
  • 100mm Apochromatic Refractor OTA
  • 380mm Focal Length, f/3.8 Focal Ratio
  • Super and Extra-Low Dispersion Glass
  • Anti-Reflection Fully Multicoated Optics
  • Large Non-Rotational Helical Focuser
  • Prime Focus, Afocal, Projection Imaging
  • Mounting Threads for Imaging Rings
  • Designed to Cover Medium-Format Sensors
  • Hard Aluminum Carrying Case
  • OTA Only - Mount and Tripod Required
The VSD100 100mm f/3.8 Astrograph Refractor from Vixen Optics is a purpose-built telescope for astrophotography and astro-imaging, with an imaging circle capable of covering up to medium-format 645 sensors. Optically, it's designed with a fully multicoated 5-group/5-element apochromatic lens system that corrects for spherical and chromatic aberrations. This correction creates a wide flat field of view without distortion and removes the blue-tinted "halo" affect for true high-contrast color transmission. Astigmatic and coma aberrations are also corrected. Front M112x1 and rear M58x0.75 threads allow the use of filters that can stay on, even if the user wants to change cameras.

The scope can be used for multiple astrophotography techniques included prime-focus, afocal imaging, or eyepiece projection. A traditional focuser is replaced by a non-rotational helical focus system which moves the drawtube forward or back to place the focal point onto the camera's imaging sensor. The vernier scale on the drawtube is engraved for durability and repeatability and enables precision measurements to as much as 20 microns. Three different size camera adapters are provided to accommodate the most common camera-specific T-rings and accessories.

Optical Performance
  • 100mm aperture
  • f/3.8 focal ratio
  • 380mm focal length
  • Apochromatic 5-group/5-element lens design corrects for spherical and chromatic aberrations
  • Views show a wide and flat field of view without distortion at the edges - spherical aberration
  • Colors are faithfully rendered by eliminating the blue "halo" effect of chromatic aberrations
  • Astigmatism and coma aberrations are also corrected
  • Anti-reflection fully multicoated optics
  • Use for prime focus, Afocal imaging, or eyepiece projection astrophotography
  • Push fit: 60.2mm and 31.7mm
  • M84x1.0, M60x0.75mm, M42x0.75mm camera adapter threads
  • 70mm imaging circle, with approximately 60% illumination at the edge
  • Designed to cover a 645 medium format sensor
  • 58mm filter thread
  • 89mm diameter drawtube
  • Knurled non-rotational helical focus ring
  • Focus ring lock sets drawtube in place
  • Precision vernier scale on the drawtube for exact focal point placement to 20 microns
  • Vernier scale engraved on drawtube for durability
Construction Details
  • Anodized aluminum optical tube
  • 1/4"-20 tripod mount
  • M112x1 objective filter thread
  • Hard aluminum carrying case

In the Box

Vixen Optics VSD100 100mm f/3.8 Astrograph Refractor

  • 3 x Photo Adapter Rings
  • 1.5mm Allen Wrench
  • Hard Aluminum Case
  • Limited Five-Year Warranty


    If there is one thing that causes angst among astrophotographers, it is the appearance of misshapen stars at the periphery of the field of view in deep-sky images. The Vixen VSD 100 f/3.8 astrograph tackles this issue head-on with a new optical design comprised of five individual lens elements.
    The VSD 100 is supplied in a substantial flight case, the diminutive dimensions of which are a bit of a surprise when you first open the outer packaging, but this telescope is small for a very good reason. The clue is in the extremely low focal ratio of f/3.8 which, with an aperture of 4 inches, translates into a very short focal length of just 380mm.
    Objects such as emission nebulae can extend across a surprising amount of sky: capturing these objects in their entirety requires a wide field of view, which dictates a short focal length. The VSD 100 has been specifically designed to cover a very wide yet flat field of view.
    Vixen has not merely considered the optical requirements for this type of photography, as it has also included a very different type of focuser to normal refractors. The helical focuser supplied is beautifully engineered and held our imaging equipment very solidly indeed – there was absolutely no chance of any slippage while imaging near the zenith. The action is firm but smooth and produced no image shift when changing focus direction.
    The focuser has a vernier scale rather than a simple, graduated one, and this allows the focus position to be read to an accuracy of 0.02mm. If you are not used to reading a vernier scale this can take a little getting used to, but for logging the start position for various camera and filter combinations, it can be invaluable.

    Small but powerful

    Supporting the optics and focuser is a white, high gloss tube and dew shield. Fit and finish are exemplary, with the micro-baffling and extremely matt black internal surfaces with absolutely no reflective areas showing great attention to detail. The various components have been engineered to very close tolerances and the main adaptor that slides into the focuser drawtube was such a perfect fit that it blew the dust cap off the rear of the telescope when inserting it.
    Daytime imaging tests with a Canon EOS 450D DSLR camera indicated good colour correction. In fact, this telescope would be excellent for capturing high-quality wildlife images, especially as its handling has much in common with a camera lens. However, under the much more demanding spotlight of deep-sky imaging using a one shot colour CCD camera, we found it tricky to achieve best focus. Our Bahtinov mask and confirmation of correct focus using MaxIm DL’s FWHM tool resulted in images that were not quite as sharply focused as we would have hoped for.
    Switching to a monochrome CCD camera, we again noted that luminance data was not as critically sharp as we had expected, with a little bloating to brighter stars. However, capturing narrowband data using our 7nm hydrogen-alpha (Ha) and oxygen III (OIII) filters produced extremely finely focused results, indicating that the optics are not entirely apochromatic.
    We were very impressed with the flatness of the field of view. Capturing consistently well-formed stars right to the edges of the field of view with such a short focal length instrument is quite an achievement bearing in mind the actual sensor sizes involved. With our one shot colour CCD camera the field of view was 3° and 31 arcminutes by 2° and 21 arcminutes, while with our monochrome CCD camera it was 2° and 42 arcminutes by 2° and 2 arcminutes. There was some vignetting, but this was easily removed by applying flat frames.
    Vixen has succeeded in producing a short focal length instrument with a truly excellent flat field ideal for many deep-sky imaging applications. Narrowband imagers will be very satisfied but one shot colour camera users and LRGB imagers may be a little disappointed with the sharpness of their images.

    A five-fold flatness fix
    All refractors suffer from field curvature to some extent. Although this can be tolerated when using eyepieces, the flat nature of a camera’s sensor highlights the issue. Images captured through a normal refractor show elongated stars at the edges of the field of view because a curved plane of focus projected onto a flat surface results in just the centre of the field achieving focus. These abnormal star shapes detract from the appearance of the view – which is why astrophotographers go to great lengths to eliminate them by installing external field flatteners.
    Some manufacturers use a four-element optical configuration based on the original Petzval design in an attempt to combat field curvature, with some success. However, the single most important design feature of the Vixen VSD 100 is its five-element, five-group optical configuration. Vixen has resolved the flat field issue by using a pair of lenses at the front of the telescope to focus the incoming light and a set of three additional lenses at the rear of the telescope to correct the field curvature, resulting in a very flat field of view.

    Internal baffles and blackening - Keeping light reflections to a minimum is important to maintain good contrast and the VSD 100 tackles this in two ways. First, the internal surfaces are coated in a very matt black finish; complementing this, there are a series of baffles within the tube to further absorb unwanted reflections.

    Dew shield - The fixed dew shield extends 98mm past the front of the telescope and provides excellent protection from stray light and the effects of dewing. The push-in dust cap is made of aluminium and is retained in a rubberised holder, providing a very simple but extremely effective barrier.
    58mm filter holder - The push-fit adaptor that couples directly with the focuser’s drawtube has an internal thread for holding a standard 58mm filter. This feature allows a light pollution filter to be installed for use with a one shot colour camera such as a DSLR.
    Helical focuser and vernier scale - Unusually, the VSD 100 is supplied with a helical focuser, which operates in the same manner as a camera lens – adjustment is made by turning a focusing ring. The Vixen version is very substantial indeed, easily supporting our imaging gear with a superb focus action and a vernier scale for logging focus positions.
    1.25-inch eyepiece holder - Although designed primarily for astrophotography, the VSD 100 is packaged with a basic 1.25-inch eyepiece holder. There isn’t sufficient backfocus to allow the use of a star diagonal, so observations must be made in a straight-through manner, which is quite typical of other Japanese telescopes.

    This review originally appeared in the October 2014 issue of BBC Sky at Night Magazine.

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