Vixen BT81S-A Astronomy Binoculars
  • Vixen BT81S-A Astronomy Binoculars

Vixen BT81S-A Astronomy Binoculars

This 81mm astronomy binocular delivers crystal clear, sharp views through its new optical design. Its lightweight body ensures that you can take it to any observing location.

The air-spaced doublet optics in this 81mm are magnesium fluoride coated to help reduce the effects of chromatic aberration.

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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 for this excellent "space binocular".


Model BT-ED70S-A BT81S-A
Objective lens D=70mm F=400mm ED Apochromatic, multi-coated D=81mm F=480mm Achromatic, single coating with Mgfl
Limiting magnitude 11.0 11.3
Light gathering power 100x 134x
Dimensions L400 x W190 x H155 L480 x W190 x H155mm
Weight 4.0kg (8.8lb) 4.1kg (9lb)
Visual back 31.7mm push fit 31.7mm push fit
Eyepieces (optional) SLV and LVW with 31.7mm are recommended excluding LV8-24 Zoom SLV and LVW with 31.7mm are recommended excluding LV8-24 Zoom
Accessories included Finder bracket shoe, carry handle & dew shields Finder bracket shoe, carry handle & dew shields

Note: The BT81S-A is not designed for viewing at high magnification. Use of eyepieces with focal length shorter than 10mm is not recommended. Eyepieces are not supplied as standard with the BT-ED70S-A or BT81S-A.

Optional Accessories

Fork Mount
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 SXG-HAL130 or SXG-AL130 tripods. (73798 Swing Bracket required for use with BT-ED70S-A and BT81S-A.)
Weight: 3.4kg
Maximum loading weight: 13kg
73798 Swing Bracket for HF2 Mount
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.

Product Code
Field (m) 
Eyerelief (mm)
IPD (mm)
HxW (mm) 
Weight (g) 


74304 14304

Data sheet

What Is your interest?
Distant Object Using a Tripod
What size do you want?
Tripod mounted

Specific References