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Vixen Optics 25x81 BT81S-A Astronomical Binocular OTA ( Award Winning Binocular Telescopes)
Vixen Optics 25x81 BT81S-A Astronomical Binocular OTA ( Award Winning Binocular Telescopes)

Vixen Optics 25x81 BT81S-A Astronomical Binocular OTA ( Award Winning Binocular Telescopes)

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Your Price: CAD1,960.44
Out of Stock
Part Number:14304

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Product Highlights

  • Erect Image Binocular Viewing
  • Aperture of 81mm
  • Focal Length of 480mm
  • 45-Degree Angled
  • Magnesium Fluoride Coated
  • Individual Focus
  • Carry Handle
  • Finder Bracket

The 81mm BT81S-A Astronomical Binocular - OTA from Vixen Optics is an astronomical observation binocular allowing interchangeable eyepieces that provides exceptional terrestrial or celestial observing. The twin 480mm f/5.9 achromatic refractors have permanently attached 45° diagonals. They accept the entire lineup of Vixen NPL Plossl eyepieces and have an enormous 56-101mm interpupillary adjustment range to work with nearly any set of eyes, including many children's.

For remarkable depth perception and contrast, there is nothing that beats the ease and comfort of erect image binocular viewing. Expect high quality observing of terrestrial vistas and celestial views alike which is easily transported to your favorite dark sky location out and beyond. Take a drive to nowhere on a clear, new moon lit night and be awe struck! The Pleiades and the Moon's terminator never looked like this.

This permutation of the BT81S-A arrives with the binocular optical tube assembly (OTA) only. Eyepieces, mount and a tripod or base need to be supplied by the user.

Accepts multiple 1.25" eyepieces
Visual back 31.7 mm - friction fit
Built-in carry handle and finder bracket
Mount block dovetail bar for SX/GP tripods
Interpupillary distance adjustment range of 2.2-4.0"
Resolving power of 1.43 arc seconds and light gathering value of 134x
Twin 480mm f/5.9 achromatic refractor telescopes with 45° incorporated erect image diagonals


Objective Lens Diameter
Angle of View
2.0° (actual)
105' @ 1000 yd / 34.86 m @ 1000 m
Minimum Focus Distance
Not Specified By Manufacturer
Exit Pupil Diameter
3.24 mm
Eye Relief
19.5 mm
Interpupillary Adjustment
55.88 - 101.60 mm / 2.2 - 4.0"
Dioptric Correction
Focus Type
Tripod Mount
18.9 x 7.4 x 6" / 48.01 x 18.80 x 15.24 cm
9 lb / 4.08 kg 1
Please Note:
optical assembly only

In the Box
Vixen Optics 81mm BT81S-A Astronomical Binocular - OTA
  • Mount Block
  • Lifetime Transferable Warranty

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