Orion XT12 - Manual (Page 8)

8
Placing the Optical Tube on the Dobsonian Base
Lift the optical tube and gently place it into the Dobsonian
base so that the altitude bearings on either side of the tube
rest on the bearing cylinders. Be careful when doing this, as
the optical tube is somewhat heavy and unwieldy. Orient the
optical tube as shown in Figure 16. Make certain that the
optical tube does not get hung up on the vertical stop or the
CorrecTension pads as you put it in place. Also make cer-
tain not to angle the tube so its altitude bearings can strike
the encoder connector board and potentially damage it. Once
on the bearing cylinders, the tube should pivot freely up and
down with gentle hand pressure. Note that the tube will not yet
be properly balanced, since the eyepiece and finder scope
are not in place, and the CorrecTension system has not been
installed.
Installing the CorrecTension Friction
Optimization System
An exciting feature of the SkyQuest IntelliScope Dobsonian is
the redesigned CorrecTension (XT) system. Because of their
relatively light weight, smaller Dobsonians (under 16") have
always been plagued by insufficient friction on the altitude
bearing surfaces. As a result, such telescopes move up and
down much too freely. This causes problems when the observ-
er tries to accurately center and track an object for viewing,
especially at higher powers. Also, the telescope becomes very
sensitive to balance, requiring additional equipment such as
counterweight systems or springs to compensate.
SkyQuest Intelliscope Dobsonians employ a simple yet effec-
tive remedy for the friction problem that obviates the need for
such cumbersome countermeasures. CorrecTension Friction
Optimization utilizes a simple “disc brake” to apply the correct
level of tension to the altitude bearings. With the XT system,
you can change eyepieces or add a barlow lens without hav-
ing to tediously adjust the telescope’s balance as you would
with other Dobsonians. The altitude friction can be made
equal to the azimuth friction, ensuring optimal performance.
To install the XT system, follow these steps
while referring to Figures 17 and 18:
1. Select one of the retaining/tensioning knobs and slide the
metal washer onto shaft, followed by the white nylon wash-
er (you will need to thread this washer onto the shaft). This
knob will now be known as the tensioning knob. Push the
shaft of the tensioning knob through the hole in the side
panel that has the IntelliScope port (Figure 17). Thread
the knob into the altitude bearing until the CorrecTension
pads on the interior surface of the side panel just touch
the side of the altitude bearing on the optical tube.
2. Place the black nylon retaining knob spacer on the shaft
of the remaining retaining/tensioning knob. This knob will
Figure 15. Using the two supplied screws, install the aluminum
eyepiece rack in the predrilled holes near the top of the front
baseplate.
Figure 16. Lift the optical
tube and place it onto the
Dobsonian base so that the
altitude bearings rest on the
bearing cylinders. Orient
the optical tube as shown.
Do not bump the encoder
connector board or vertical
stop when installing the
optical tube.
Figure 17. The tensioning knob, with the metal and nylon
washers, goes on the side of the base with the IntelliScope port.
The tensioning knob should be tightened until the CorrecTension
pads just touch the telescope’s altitude bearing.