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USING YOUR BT81S-A BINOCULAR TELESCOPE
1
The 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.
1
Camera tripod
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.
3
Left side focus ring
Left side focus ring
ALIGNMENT
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.
How to Adjust a Double Vision
1
Look 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 GENERAL 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.)
Dovetail bar
Dovetail bar
1/4" -20
1/4" -20
3/8"
3/8"
Right side focus ring
Right side focus ring
VIXEN - European Distributor Bresser GmbH Gutenbergstrasse 2, D-46414 Rhede, Germany
Phone: +49 (0) 2872 – 80 740
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.
2
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.
4
Left side
Left side
prism housing
prism housing
Left
1
Imaginary horizontal line
2
Left
E-Mail: info@bresser.de www.bresser.de
Eyepieces
Eyepieces
(Optional)
(Optional)
Eyepiece holder
Eyepiece holder
prism housing
prism housing
Shift the object to the very right edge
Right
Right
Chrome
Chrome
barrel
barrel
Right side
Right side
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