Truss connector knob

Registration flats

Upper truss support ring

Truss connector

Figure 27. When the knob in the truss connector is tightened, it will clamp the truss connector against the registration flats on the upper truss support ring.

Altitude side bearing

Altitude tensioning metal washer

Altitude tensioning

Teflon washer

Altitude tensioning knob

IntelliScope port

Figure 28. Lift the optical tube by grasping two truss poles and carefully lower it so that the large altitude bearing hubs rest on the altitude bearing cylinders on the side panels.

9.Firmly tighten the eight clamping knobs on the lower truss support ring.

10.If, after assembling, the truss poles are loose within the truss connectors, use the supplied 4mm hex key to tight- en the button head cap screws which connect the poles to the truss connectors (see Figure 26). This should rare- ly need to be done.

The telescope is now assembled and ready to be placed into the Dobsonian base.

Figure 29. Insert the shaft of the altitude tensioning knob, with metal and Teflon washers attached, into the side of the base with the IntelliScope port, and thread it into the tube’s altitude side bearing.

Mounting the Optical Tube on the

Dobsonian Base

1.Grasp two opposing truss poles as shown in Figure 28 and lift the optical tube, then gently place it into the Dobsonian base so the altitude bearings on either side of the tube rest on the base’s bearing cylinders. Be careful when doing this, as the optical tube is somewhat heavy and unwieldy. Orient the optical tube on the base as seen in Figure 1. Make certain the optical tube does not get hung up on the vertical stop or the CorrecTension pads (i.e. the three square white pads on the inside surface of the left side panel) as you put it in place. Also, be very careful not to hit the altitude encoder with the side bear- ing on the tube when doing this or damage to the encod- er could result. The bumper is positioned to help prevent such contact. Once on the bearing cylinders, the tube should pivot freely up and down with gentle hand pres- sure. Note that the tube will not yet be properly balanced, since the eyepiece and finder scope are not in place, and the altitude tensioning knob has not been installed.

2.Select one of the altitude tensioning/retaining knobs (they are the same) and slide the tensioning knob metal washer onto the shaft, followed by the tensioning knob white Teflon washer (you will need to thread the Teflon washer onto the shaft, this keeps both washers captive on the knob’s shaft). These parts are found in the box with the Dobsonian base. Push the shaft of the knob through the hole in the side panel that has the IntelliScope port (Figure 29). Thread the knob into the optical tube’s alti- tude bearing until the knob pulls the altitude bearing

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Image 17
Orion 9791 instruction manual Mounting the Optical Tube on Dobsonian Base