Vixen BT81S-A User manual

Instruction Manual for BT81S-A Binocular Telescope
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.
WARNING!
SPECIFICATIONS
COMPONENTS
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.
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.
CAUTION HANDLING・STORAGE
BT81S-A Shown with the Fork Mount,
Tripod and other Optional Accessories available separately
* 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 and SXG-HAL130 tripod.
Objective lens
Optical coating
Effective aperture
Focal length (Focal ratio)
Resolving power
Limiting magnitude
Light gathering power
Eyepiece holders
Eyepieces applicable
(Optional)
Interpupillary distance
Optional Accessories
Mount block / Threads
Threaded sockets
Size & weight
Air-spaced doublet achromatic
Magnesium fluoride coating
81mm
480mm (F/5.9)
1.43 arc seconds
11.3
134x
Friction fit type
SLV series of 31.7mm size or LVW series of
31.7mm size or SSW series of 31.7mm size
58mm to 102mm
7x50mm finder scope & bracket or X-Y
red dot finder
Dovetail bar for SX/GP
1/4-inch x 2 & 3/8-inch x 1
480mm L x 190mm W x 155mm H, 4.1kg (9 lbs)
Carry Handle
Optical Tube
Dew Shield
Objective Lens
(inside)
Eyepiece Holders
Friction Fit
Focus Ring
Prism Housing
45-degree Angled
Finder-bracket Shoe
Dovetail Bar
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.
SXG-HAL130 Tripod(Optional)
BT81S-A
Threded sockets
for camera tripod
Swing Bracket
(Optional)
HF2 Fork mount
(Optional)
7x50 Finder Scope
(Optional)
XY Finder bracket
(Optional)
Eyepieces
(Optional)
Objective Cap
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.

USING YOUR BT81S-A BINOCULAR TELESCOPE
ALIGNMENT
1The BT81S-A has threaded sockets of 1/4”-20 and a
3/8” on the bottom of the dovetail bar that fit directly
to a camera tripod.
3
While looking through the right side eyepiece, turn the focus
ring on the right side prism housing until the image appears in
sharp focus. Next, look through the left side eyepiece and
adjust the focus of the left side eyepiece in the same way by
turning the left side focus ring.
2
Attach the eyepieces so that the chrome barrel of the eyepiece
is push into the eyepiece holder and fixed by friction. When
you exchange the eyepieces, you should align the optical axis
of left side and right side eyepieces in the procedure stated in
ALIGNMENT.
4
Adjust the interpupillary width to your eyes. Hold the left and
right side prism housings with both hands and rotate them
inward equally so that the both eyepieces come to a position
that fits your eyes. It is a point that circles of field of view in the
left and right eyepieces become one completely.
How to Adjust a Double Vision
1Look through the left side eyepiece and find an object
further than 1,000m distant. Put the object in the field of
view so that it lies on the imaginary horizontal center line of
the field of view, and shift it to the very right edge. An
electric pole is shown here as a sample.
The object near the edge of the field of view makes your
recognition of a position of the object against the field of
view circle easier.
If the object is seen at the same level and position on the
right side eyepiece as seen with the left side eyepiece, it
shows that the eyepieces are aligned correctly.
If not, rotate the right side eyepiece slowly clockwise or
counterclockwise until the object moves toward the same position.
2
If the above does not align the optics correctly, then rotate
the left side eyepiece slowly while keeping the right side
eyepiece as it is.
TIPS ON GENRAL OBSERVATION WITH BT81S-A
The object can be seen more clear and brighter at low
magnification. It is desirable to start with a pair of eyepieces with low magnification and exchange them for eyepieces with
medium magnification. It will be hard to align the optical axis at high magnification due to the structure of binocular telescopes.
(It is advisable to use with the Vixen SLV or LVW eyepieces with focal length longer than 10mm at high magnification.)
It may be possible that a double vision occurs from the character of binoculars when you attach the eyepieces without
a consideration for optical alignment. In this case, make adjustments of the optical axis in the following procedure.
1left
Right
Right
left
1 2
3 4
2
Dovetail bar
1/4”-20
3/8”
Right side
prism housing
Left side
prism housing
Eyepieces
(Optional)
Eyepiece holder
Chrome
barrel
Camera tripod
Left side focus ring
Dovetail bar
1/4”-20
3/8”
Right side
prism housing
Left side
prism housing
Eyepieces
(Optional)
Eyepiece holder
Chrome
barrel
Camera tripod
Left side focus ring
Right side focus ring
Right side focus ring
Imaginary horizontal center line
Shift the object to the very right edge
67k-2-0.2S-(DC1450GA)(M)
5-17-3 H igashitokorozawa,Tokorozawa,Sa i tama359-0021, Japan
Phone [phone](International)
F a x [phone](International)
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