Altitude side bearing 
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Phillips head | 1/4" washer | |||||||
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Pull loop |
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Figure 13. Close-up view of the CorrecTension system.
panel of the base you will notice two predrilled starter holes, about 6" apart. Take the black wood screws and thread them into the starter holes with a Phillips screwdriver. Then you can “keyhole” the eyepiece rack onto the wood screws and con- tinue tightening the screws (Figure 11). If you want to be able to remove the rack, do not tighten the screws too tightly. Be certain the screws are loose enough so you can lift the rack and remove it from the screws through the larger part of the keyhole. If you want to have the rack permanently attached, thread the screws tightly.
Placing the Optical Tube on the Dobsonian Base
Lift the optical tube and set the altitude bearings on either side of the tube in the “cradle” of the base (Figure 12). The unique flange design of the altitude bearing allows for automatic left-
Installing the CorrecTension (XT)
Friction Optimization System
Perhaps the most exciting new feature of the SkyQuest XT12 Dobsonian is the CorrecTension Friction Optimization sys- tem. Because of their relatively light weight, 12" and smaller Dobsonians 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 observer tries to accurately center and track an object for viewing, especially at higher powers. Also, the tele- scope becomes very sensitive to balance, requiring additional equipment such as counterweight systems or adjustable side bearings to compensate.
SkyQuest XT12 Dobsonians employ a simple yet effective remedy for the friction problem that obviates the need for such cumbersome countermeasures. CorrecTension Friction Optimization utilizes a spring coil to “pull” the tube assem- bly down onto the altitude bearing pads, thereby increasing the friction by just the right amount. With CorrecTension, you can change eyepieces or add a barlow lens without having to tediously adjust the telescope’s balance as you would with
a.
b.
Figure 14. (a) To attach the spring to the base, grip the pull loop with your index finger and pull down on the spring. (b) While pulling down, slip the end ring of the spring over the screw head and onto the narrow part of the nylon spacer, then release the pull loop.
other Dobsonians. The altitude friction will roughly equal the azimuth friction, ensuring optimal performance.
To install the CorrecTension assembly, follow these steps while referring to Figure 13:
1.Put one of the black nylon spacers on a black Phillips head screw. The spacer should be oriented so the narrow end seats against the head of the screw. Slip one of the black 1/4" washers over the end of the screw. Now, thread the screw into the hole in the base side panel just below the cradle. The screw will thread into the preinstalled insert in the hole. Use a Phillips screwdriver to tighten the screw. Repeat this procedure on the opposite side panel.
2.Next, insert one of the screws with round plastic knob attached through the end ring of one of the springs. Slip a black nylon spacer onto the screw. Orient the spacer so the narrow end is closest to the knob. Thread the entire assembly into the hole in the center of the telescope’s alti- tude side bearing until tight. The end ring of the spring
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