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BT81S-A Shown with the Fork Mount,
Tripod and other Optional Accessories available separately
Instruction Manual for BT81S-A Binocular Telescope
WARNING!
SPECIFICATIONS
COMPONENTS
BT81S-A Shown with the Fork Mount,
Tripod and other Optional Accessories available separately
Never look directly at the sun with your naked eyes or through this product or its finder scope available.
Permanent and irreversible eye damage may result.
Thank you for your purchase of a Vixen BT81S-A Binocular Telescope. This manual applies to the BT81S-A Binocular Telescope.
Be sure to read instructions for the mount and tripod along with this manual if you purchased the product as a complete package
*For observing, two 31.7mm (1.25-inch) eyepieces of the same focal length are required as they are not included.
*A pair of the eyepieces are included if you purchase a complete package consisting of the BT81S-A, HF2 Altazimuth Fork Mount ans SXG-HAL130 tripod.
Do not leave the product uncapped in daytime. It may cause passing sunlight through
the objective lens of the optical tube, resulting in fire
Do not use the product while transporting or walking, as injuries may arise from
stumbling, falling or collision with objects.
Keep plastic and vinyl packing materials away from children; these may cause danger
from swallowing or suffocation.
The specifications are subject to change without notice.
About eyepieces applicable to BT81S-A
The detachable eyepieces can be swapped for other Vixen SLV or LVW or SSW series
of 31.7mm-size eyepieces, but if the eyepieces with high magnification are used, it
may give rise to misalignment that is become detectable due to its high magnification.
It is always recommendable to use the eyepieces with focal length longer than 10mm
for observing to avoid it.
Do not leave the product inside a car in bright sunshine, or in hot places. Keep any
strong heat radiation sources away from the product.
Do not exposure the product to rain, water drops, dirt or sand.
When cleaning, do not use solvent such as paint thinners.
Avoid touching any lens surfaces directly with fingers. If a lens becomes dirty with
fingerprints or general smears, gently wipe it using a commercially available lens leaner
and a lens cleaning paper, or consult your local Vixen dealer.
For storage, keep the product in dry places, and do not expose to direct sunlight.
CAUTION
HANDLING • STORAGE
Objective lens
Air-spaced doublet achromatic
Optical coating
Magnesium fluoride coating
Effective aperture
81mm
Focal length (Focal ratio)
480mm (F/5.9)
Resolving power
1.43 arc seconds
Limiting magnitude
11.3
Light gathering power
134x
Eyepiece holders
Friction fit type
Eyepieces applicable
(Optional)
SLV series of 31.7mm size or LVW series of
31.7mm size or SSW series of 31.7mm size
Interpupillary distance
58mm to 102mm
Optional Accessories
7x50mm finder scope & bracket or X-Y red
dot finder
Mount block / Threads
Dovetail bar for SX/GP
Threaded sockets
1/4-inch x 2 & 3/8-inch x 1
Size & weight
480mm L x 190mm W x 155mm H, 4.1kg (9 lbs)
Carry Handle
Objective Cap
BT81S-A
Threaded sockets
for camera tripods
7x50 Finder Scope
(Optional)
XY Finder bracket
(Optional)
Eyepieces
(Optional)
Swing Bracket
(Optional)
SXG-HAL130 Tripod
(Optional)
HF2 Fork mount
(Optional)
Eyepiece Holders
Friction Fit
Focus Ring
Prism Housing
45-degree Angle
Finder-bracket Shoe
Dovetail Bar
Optical Tube
Dew Shield
Objective Lens
(inside)
