BT81S-A Binocular Telescope
 BT81S-A Binocular TelescopeBT81S-A Binocular Telescope 

BT81S-A Binocular Telescope

  (1 Review)
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About this product

Model:  BT81S-A
Part Number:  74304

With Japanese-made 81mm air-spaced doublet optics, magnesium fluoride coatings and 45-degree prism-blocks this is an excellent binocular for astronomy or long distance terrestrial observing. 

The eyepiece holders are set at 45-degrees for comfortable observing. This is particularly beneficial when using the binocular for astronomy.  

Mounting the binoculars is a simple process as they come supplied with a Vixen dovetail mounting bar for use with equatorial or altaz mounts. The dovetail bar also has 1/4" thread sockets for use with conventional tripod panheads.

An optional altaz fork mount is available and allows the binoculars to be used on the optional SX-HAL130 or SXG-HAL130 tripods. These provide a stable but lightweight tripod base.

Eyepieces are not supplied as standard with this binocular.

Most astronomy eyepieces with 1.25" barrels and 10mm (48x) to 40mm (12x) focal lengths will work well. Vixen SLV eyepieces are an excellent match.

Optional Accessories



78062 HF2 Fork Mount

Provides an easy-to-use friction controlled altazimuthal mounting for the Vixen range of astronomy binoculars and other optical devices. The fork mount comes complete with a half-pillar to raise the binoculars to a comfortable viewing height. Fits onto the SX-HAL130 or SXG-HAL130 tripods. Requires the 73798 Mount Plate.

Weight: 3.4kg
Maximum loading weight: 13kg


73798 Mount Plate

Required to allow the 78062 Fork Mount to be used with astronomy binoculars and any other optical devices which have a 1/4" screw thread socket.




What's in the box

  • 81mm Astronomy Binocular
  • Finder Bracket Shoe
  • Carry Handle
  • Dew Shields


Aperture RatioF/5.9
Aperture81mm (3.1")
Focal length480mm.
Resolving Power 1.43 arc sec.
Light Gathering 134x
Interpupillary Distance 2.2" to 4"
Mount Block Dovetail Bar for SX/GP Tripods
Visual Back 31.7 mm - Friction Fit
Dimensions 18.9 x 7.4 x 6 inches
Features Carry Handle, Finder Bracket
Weight9 lbs

Customer reviews

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BT81S-A Reviewed
Sunday, 2 November 2014  | 

I purchased the complete set of binoculars, fork mount, plate and tripod as a birthday present. The recipient is very happy with the set. It screams quality and robustness. Easy to set up and move around despite its mass. Views have been impressive, no mis-collimation and pin point stars to the edge. Was able to comfortably view the Perseus Double Cluster when near the zenith. Definitely worth the money. The set came with the upgraded 25mm SLV eyepieces.


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