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Orion BX90 Instruction Manual page 7

90mm equatorial refractor

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Gear shaft
A
B
Figure 8.
)
A
Slide the slow-motion cable onto the gear shaft as
)
shown, B
then thread the knurled nut into the threaded end of the
cable until tight.
setting is used under dark skies and the brighter setting is
used under light-polluted skies or in daylight.
4. You'll want to center the target object on the red dot. To do
so, without moving the telescope, use the finder scope's
vertical and horizontal adjustment knobs (shown in Figure
13) to position the red dot on the object.
5. When the red dot is centered on the distant object, check
to make sure the object is still centered in the telescope's
eyepiece. If it isn't, re-center it then adjust the finder
scope's alignment again. When the object is centered in
the telescope eyepiece and on the finder scope's red dot,
the finder scope is properly aligned with the telescope.
The red dot finder scope's alignment should be checked
before every observing session.
At the end of your observing session, be sure to slide the power
switch on the red dot finder scope to OFF to preserve battery life.
Knurled
knob
Pins
Slots
Slow-motion
cable
Tube
mounting
clamp
Saddle
A
Figure 9.
)
A
Install the tube mounting clamp onto the mount
saddle. B) Secure the clamp to the saddle with the two wing nuts.
Balancing the Telescope
In order for the telescope to move smoothly on its mechanical
axes, it must first be balanced as follows:
1. Keeping one hand on the telescope optical tube, loosen
the R.A. lock knob. Make sure the Dec. lock knob is locked,
for now. The telescope should now be able to rotate freely
about the R.A. axis. Rotate it until the counterweight shaft
is parallel to the ground, i.e., horizontal (Figure 14A).
2. Now loosen the counterweight lock knob and slide the
weight along the shaft until it exactly counterbalances the
telescope. That's the point at which the shaft remains hori-
Figure 10.
Lay the optical tube in the open clamp, then close the
clamp and lock it in with the clamp lock bolt.
Washer
Wing
nut
B
Lock bolt
7

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