Discover Vixen’s SD81SII Apochromatic Refractor, a compact yet powerful photo-visual telescope designed to deliver both exceptional astrophotography performance and vivid visual observations. With a 625mm focal length, this versatile OTA is ideal for stargazers and astrophotographers seeking sharp, high-contrast views of celestial objects.
At the heart of the SD81SII is Vixen’s renowned Super Extra-Low Dispersion (SD) optical glass, engineered to minimize chromatic aberration and produce crisp, color-accurate images. Whether you're capturing star fields or observing planetary detail, the SD glass ensures top-tier optical quality.
Unlike its predecessor, this upgraded model features a ring spacer around the objective lens — a seemingly small improvement that makes a big difference. Traditional tin foil spacers caused diffraction artifacts and uneven star shapes in images. The new ring spacer eliminates that problem, enabling uniform diffraction patterns for beautifully refined star images — a significant advantage for astrophotography.
When paired with the optional SD Reducer HD Kit or SD Flattener HD Kit, the SD81SII supports a full 44mm image circle, making it perfect for use with full-frame DSLR cameras.
The SD lens minimizes residual chromatic aberration to a level well below visible detection, ensuring exceptionally sharp and color-accurate images.
Refractor telescopes can sometimes show color fringing around bright objects because different colors of light focus at slightly different points. Vixen’s SD lenses use special extra-low dispersion glass to correct this, giving you clearer, sharper, and more true-to-color views.
This graph shows how Vixen’s SD lenses bring all visible colors of light—from red to violet—into focus at nearly the same point along the optical axis. Each curve represents a different wavelength of light, and their close alignment near zero shows how effectively the SD glass corrects chromatic aberration. This includes the violet “g-ray,” which is especially important for preserving image contrast. The result is exceptionally sharp, high-contrast views with minimal color fringing, making the SD81SII a powerful tool for both visual observation and astrophotography.
The short optical tube makes the telescope easy to manage and ideal for both stargazing and astrophotography.
This diagram illustrates the internal light path and compact design of the Vixen SD81SII optical tube. Its moderately short length and lightweight build make it easy to carry, balance, and mount with minimal counterweights. The scope comes equipped with a metal carry handle and a Vixen-standard dovetail bar for quick attachment and detachment. Also shown is the flip mirror diagonal, which directs incoming light either to an eyepiece or a camera. This allows users to quickly switch between visual observation and astrophotography without changing the setup.
Full-frame imaging with a DSLR camera.
This stunning image of the Lagoon Nebula (M8) and Trifid Nebula (M20) showcases the astrophotography potential of the Vixen SD81SII when paired with the optional SD Reducer HD Kit. Captured using a Pentax K-1 DSLR at ISO 1600 with a 49-minute total exposure, the setup achieved a 496mm compound focal length and a 44mm image circle—ideal for full-frame sensors. The result is a richly detailed and wide-field view of deep-sky targets, demonstrating how the SD81SII excels in producing crisp, high-contrast images across the entire frame.
Optional accessories to enhance your astrophotography experience.
The SD Reducer HD Kit is a powerful accessory combination for the Vixen SD81SII, SD103SII, and SD115SII optical tubes. It includes a field flattener and a focal reducer, working together to create a flat, wide imaging field—perfect for capturing full-frame astrophotos with sharp stars from edge to edge. The reducer shortens the focal length by 0.7×, giving you a broader view of the night sky without sacrificing image quality.
Paired with the Direct Wide Photo Adapter 60DX—available for Canon EOS and Nikon DSLRs—you can easily rotate your camera to fine-tune framing and composition. These optional accessories are ideal for astrophotographers looking to expand their imaging capabilities with precision, flexibility, and ease.
Wide Photo Adapter 60DX
High-precision camera adapters for prime focus astrophotography are available as optional accessories for Canon EOS and Nikon DSLR cameras. The Wide Photo Adapter 60DX is specially designed as an integrated camera mount that minimizes vignetting, making it highly effective for use with full-frame sensors. When paired with the SD Reducer HD Kit or SD Flattener HD Kit, it ensures optimal performance with Vixen’s SD series refractors, delivering sharp, full-frame astrophotos with excellent edge-to-edge clarity.
CA Residents: Prop 65 WARNING(S)
⭐ Features & Benefits
- 81mm Super ED (FPL53) Apochromatic Doublet – Delivers razor-sharp, color-corrected views for both visual and photographic use
- New Spacer Ring Design – Replaces foil spacers to reduce diffraction and create perfectly round stars in long-exposure images
- 625mm Focal Length at f/7.7 – Balanced for contrast, resolution, and imaging flexibility
- Made in Japan – Precision craftsmanship and premium optics for elite-level performance
- Compact & Lightweight – Just 585mm long and 2.3 kg, easy to transport and mount
- Flip Mirror Diagonal – Switch effortlessly between eyepiece and camera without reconfiguring your setup
- Dual Adapter Threads – Supports both 60mm and T-thread accessories
- Compatible with SD Reducer HD & SD Flattener HD Kits – Supports full-frame imaging with pinpoint stars across a 44mm image circle
- Pairs with Wide Photo Adapter 60DX – Canon EOS and Nikon DSLR-ready with minimal vignetting
- XY Red Dot Finder II – Quickly and easily lock onto your targets
- Versatile Imaging Modes – Excellent for prime focus, eyepiece projection, or afocal photography
🌟 Who It’s For
- Intermediate to advanced astrophotographers seeking edge-to-edge clarity with full-frame sensors
- Visual observers who want a high-end refractor for planetary and deep-sky targets
- Portable telescope users who value optical precision and lightweight design
- Anyone upgrading from a basic ED scope to a premium imaging platform
🎯 What You’ll Be Able to See
- Craters, valleys, and mountain ranges on the Moon in crisp relief
- Sharp planetary features on Jupiter, Saturn, and Mars
- Deep-sky gems like the Lagoon and Trifid Nebulae, Pleiades, and Andromeda
- Wide-field star fields with pinpoint stars — perfect for large sensor cameras
- Solar eclipses and bright terrestrial landscapes (with proper filters)
🎒 What’s Included
- Vixen SD81SII Optical Tube Assembly (OTA)
- Flip Mirror Diagonal (50.8mm / 31.7mm)
- XY Red Dot Finder II
- Dovetail Slide Bar M (Vixen-style)
- Tube Rings
- Built-in Metal Carry Handle
- Instruction Manual
Specs
| Optical Design | Apochromatic Refractor |
|---|---|
| Aperture | 81 mm |
| Focal Length | 625 mm |
| Focal Ratio | f/7.7 |
| ED Glass | Yes (FPL53 Super Extra-Low Dispersion) |
| Resolving Power | 1.43 arc seconds |
| Light Gathering Power | 134× (unaided eye) |
| Focuser | Rack-and-pinion with lock knob |
| Finder Scope | XY Red Dot Finder II |
| Visual Back | 50.8 mm and 31.7 mm with Flip Mirror Diagonal |
| Adapter Threads | 60 mm and 42 mm for T-Ring |
| Imaging Compatibility | Prime Focus, Eyepiece Projection, Afocal |
| Dimensions / Weight | 90 mm Ø × 585 mm / 3.6 kg (Net 2.3 kg) |