Ideal for visual observation and astrophotography, the Vixen Optics SD81S II Telescope Optical Tube Assembly is designed for the amateur astronomer or photographer who wants to view and photograph the moon, planets, and deep sky objects. The SD81S II features FPL53 "super" extra-low dispersion (ED) glass in a fully multicoated apochromatic lens system that corrects for both spherical and chromatic aberrations, astigmatism, and off-axis comas. This correction creates a wide flat field of view without distortion and removes the blue-tinted halo effect for true high-contrast color transmission. It can accept both 2" and 1.25" eyepieces and accessories for visual use. Threads on the drawtube allow direct connection of T-rings and other camera mounts.

Included with the optical tube assembly (OTA) is a flip-mirror diagonal with dual 1.25" holders. The light path can be directed to the upper holder with the mirror in the Up position, and to the rear holder by flipping it down. For visual observation, the mirror can hold two eyepieces to allow easy changes from low to high magnification. When using it for imaging, the camera or imaging system is placed in the back, and an eyepiece can be attached at the top to check alignment and tracking between exposures. The OTA includes a mounting ring assembly and a Vixen-style dovetail plate to make it compatible with a wide variety of mounts. An integrated carry handle makes set up and break down safe and easy.

81mm Apochromatic Refractor    625mm Focal Length, f/7.7 Focal Ratio    FPL53 Super Extra-Low Dispersion Glass    Antireflection Multicoated Optics    60mm and 42mm Adapter Threads    1.25" Dual-Holder Flip-Mirror Diagonal    Red Dot Finderscope

• Designed to capture the entire field of view of a DSLR camera with a full-frame image sensor
• 81mm aperture draws in enough light to view the moon, planets, and deep sky objects
• Fast f/7.7 focal ratio makes it ideal for long exposure astrophotography and imaging
• 625mm focal length produces a high magnification potential without being excessively long
• Refractor-style light path delivers clear and sharp image
• FPL53 extra-low dispersion glass corrects chromatic aberration across the entire visual spectrum for clearer views and images without halos or fringing
• Apochromatic lens configuration eliminates spherical aberrations that cause distortion at the edges of the field of view, and further corrects chromatic aberrations
• Anti-reflection multi-coated optics improve light transmission to produce bright and clear high-contrast images with accurate color fidelity
• Resolution: 1.43 arcsec
• 60mm and 42mm adapter threads accept T-ring and camera mounts for astrophotography and imaging
• Rack-and-pinion focusing mechanism; focus lock ensures images remain tack-sharp during long-exposure image capture
• 2" and 1.25" visual back for eyepieces and accessories
  • Optical tube assembly only—mount head and tripod required for proper use
  • Vixen-style dovetail plate is compatible with a wide variety of mount heads
  • Tube rings enable the OTA orientation to be adjusted for proper balance and to avoid interference with mount and accessories
  • Integrated carry handle for a secure set up and break down
    • Flip mirror down to direct light straight back or move it up to use upper holder
    • Enables the use of two eyepieces or a guider eyepiece and imaging system
    • 1.25" holders are compatible with a wide variety of eyepieces and accessories
    • 7x power red dot finderscope ensures a wide field of view to make alignment easy and star-hopping navigation fast

      Related Questions and Answers

      Q: 1. Why doesn't have wi-if and if not are the others (tripods) have one and why this tower tripod doesn't?

      A: The The Vixen Optics AXD2-VMC260L (WT) GoTo Catadioptric Telescope is designed for serious astrophotographers who demand a perfect imaging platform, and the Vixen Star Book Ten Go to feature of the mount, works internally with a computer, not with Wifi.

      Q: 2. Is this unitmade in japan?

      A: The Vixen Optics R130SF 130mm f/5 Reflector Telescope is made in China.

      Q: 3. Would the Celestron focal reducer work well with this scope, or does Vixen make one of their own that would?

      A: Yes you can use the Celestron f/6.3 Reducer/Corrector for this Optical Tube. Website link: http://bhpho.to/1JT4a4N Also there is the Vixen Optics 0.62x Focal Reducer for the VMC200L & VMC260L Telescopes, which will be compatible too. Website link: http://bhpho.to/1JWik5n

      Q: 4. How are the telescope focal length (1950 mm) and focal ratio (9.75) defined? Focal length is the distance from the focus to what? Focal ratio is the ratio of what to what?

      A: Focal length is the distance (given in millimeters) between the telescope's primary lens or mirror and the point where the light rays come together in focus. The focal ratio is the focal length divided by the lens diameter. For the Vixen Optics VMC200L, that would be 1950 divided by 200 = 9.75.

      Q: 5. Can I use my Meade LX85 German Equatorial mount & tripod with this OTA?

      A: Yes, you can.

      Q: 6. What type of adaptor should i buy to fit with Canon r6 markII (RF-mount)?

      A: The Tele Vue 60 2.4"/60mm Refractor would need a combination of these accessories in order to attach a Canon RF mount camera: https://bhpho.to/3jCjOKt plus https://bhpho.to/3JROjqV

      Q: 7. $22,000 is a deep investment. Why is it better than the rest? And how close can it view the surface of the moon or other celestial bodies

      A: It is a unique item with the best accessories on the market. The astroimaging camera alone is over $4,000. It still requires a mount and tripod.

      Q: 8. Does this come with a 2" diagonal?

      A: The Vixen Optics VC200L 200mm f/9 Catadioptric Telescope (OTA Only) comes with the Vixen Optics Flip Mirror System which works as a diagonal but only accepts 1.25 inch eyepieces.

      Q: 9. Does this come with supplied eye pieces and view finder?

      A: In the Box Vixen Optics ED80Sf 80mm f/7.5 APO ED Refractor Telescope with Porta II Mount Flip-Mirror Diagonal Finderscope with Bracket Hard Carrying Case for OTA Vixen Optics Porta II Alt-Azimuth Mount Limited 5-Year Warranty OTA and mount only. No eyepieces No tripod

      Q: 10. What is the size of the central obstruction(secondary+holder)?

      A: It is 3 inches.