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Vixen  |  SKU: ES26086

Vixen Optics SD103SII 103mm f/7.7 FPL-53 ED APO Refractor Telescope


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Vixen Optics SD103SII 103mm f/7.7 FPL-53 ED APO Refractor Telescope



  • 103mm / 4" Refractor-Style OTA
  • 795mm Focal Length
  • f/7.7 Focal Ratio
  • FPL53 Extra-Low Dispersion Glass
  • Apochromatic Lens Configuration
  • Anti-Reflection Multi-Coated Optics
  • 60mm and 42mm Adapter Threads
  • 1.25" Dual-Holder Flip-Mirror Diagonal
  • Mounting Rings with Vixen Dovetail
  • 7x50 Illuminated-Reticle Finderscope
  • OTA Only, Mount Head and Tripod Required


103mm aperture SD apochromatic refractor introducing a new spacer ring for more beautiful astrophotography

It is the successor to the favorably reviewed SD103S as a photo-visual optical tube that is the SD series of apochromatic refractors. With an aperture of 103mm and a focal length of 795mm, you can use it for a wide variety of purposes, from visual observation to astrophotography. We changed the spacers used around the outer periphery of the objective lens from three pieces of foil fragment to the shape of a ring to uniform the diffraction light of star image. It has obtained you a more beautiful star image. In combination with an optional SD Flattener HD Kit and an optional SD Reducer HD Kit, it develops into a high-performance astrograph providing an image circle of 44mm suitable for a camera/CMOS camera with a full frame imaging sensor.


Improved spacers for beautiful star images 

In the former SD103S optical tube, small fragments of tin foil are set at three places evenly around the lens as spacers. The small fragments that appear inside the effective aperture of the lens as protrusion generates diffractions around the star image by the light of incidence, resulting in three breaks radially around the star image. You get the star image beautifully as the diffraction light becomes uniform by exchanging the small fragments for a ring-shaped spacer.


High-performance SD glass lens that suppresses color fringing

In the refractor that gathers light using a lens, color fringing (chromatic aberration) occurs by the difference in refractive index from different wavelengths (colors) of the light that passes through the lens. Then, an invention was extra-low dispersion glass to eliminate the chromatic aberration. This glass shows less dispersion in different wavelengths of light, and its refractive index at a particular wavelength shows a value different from that of glass for general use. The SD103SII uses an SD glass (Super ED) lens made from FPL53 glass, a material that exhibits particularly excellent optical performance among ED glass. As a result, it successfully suppresses chromatic aberration at a high level and produces star images clearly and sharply. In the SD glass lens, g-ray, C-ray, F-ray, d-ray, and e-ray all come near the 0 value. That indicates the lens is excellent because the chromatic aberration is held at an extremely low level over all the visible colors. In particular, remarkably reduced aberration of the g-ray (purple) that is short wavelength enhances star images crisply.


Prepared to meet a wide range of purposes from visual observation to astrophotography

By setting a reasonable focal length (795mm) for the objective effective aperture (103mm), you can use it for a wide range of purposes, from planetary observations to photography of nebular and star clusters. The supplied flip mirror diagonal allows you to switch the optical path with a knob to straight through or vertical orientation quickly. Two eyepieces with different magnifications are usable quickly. You readily switch between visual observing and photography by attaching a camera on one side and an eyepiece on the other. The SD103SII is equipped with a standard dovetail attachment plate and a metal carry handle. Those accessories make you easily attaching to and detaching from the mount and transporting the optical tube.


Available for full-frame DSLR cameras/CMOS cameras, suitable for high-quality astrophotography

In combination with an SD Reducer HD Kit and an SD Flattener HD Kit (both sold separately), you will be ready to take high-quality astrophotography with a full-frame DSLR camera or CMOS camera.


7x50mm Finder II with Illuminated Reticle (Eyepiece unit detachable*)

A finder scope/guide scope for astronomical telescopes with a magnification of 7x and a 50mm aperture. It has crosshairs and a built-in dark field illumination, which can illuminate the crosshairs in red for sighting easily in a dark field of view. The brightness of the illumination is adjustable step by step for your preference. The eyepiece unit is a detachable type with a 31.7mm sleeve, and you can use the finder scope as a guide scope by exchanging the eyepiece unit for a commercially available CMOS camera** with a 31.7mm sleeve.

* Although you can insert 31.7mm eyepieces sold separately in the place of the eyepiece unit, this will not work as it does not reach focus.

** Regarding applicability with the CMOS cameras, you make sure that the distance from the 31.7mm visual back (rear end) on the scope body to the surface of an imaging sensor of a camera is about 15mm long or less.

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Vixen Optics SD103SII 103mm f/7.7 FPL-53 ED APO Refractor Telescope | ES26086

Vixen Optics SD103SII 103mm f/7.7 FPL-53 ED APO Refractor Telescope





103 mm | 4"

Focal Length

795 mm

Focal Ratio


Field of View



1.13 arc seconds resolution

11.8 limiting magnitude

FPL53 extra-low dispersion glass

Fully multi-coated

Barrel Size



115 mm x 810 mm


7.9 lb | 3.6 kg
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