Orion 100 EQ Getting Started, Installing the Finder Scope, Inserting the Eyepiece

Figure 4a. Figure 4b.

Proper operation of the equatorial mount requires that the telescope tube be balanced on the R.A. axis. (a) With the R.A. lock lever released, slide the counterweight along the counterweight shaft until it just counterbalances the tube. (b) When you let go with both hands, the tube should not drift up or down. The telescope should be balanced in the Dec. axis already if you have properly centered the 1/4"-20 mounting block on the optical tube relative to the tube rings.

See Part 4 for more information about the R.A. and decli- nation axes.

11.Install the polar axis finder scope into its housing inside the R.A. axis of the equatorial mount. First loosen the three thumbscrews on the housing, which is located at the rear of the R.A. axis. Insert the front end of the polar finder (the end without the eyeguard) into the housing so only about 1" of the polar finder extends from the back of the housing. Do this slowly and with a twisting motion to prevent the internal O-ring from becoming unseated. If it does become unseated, you can remove the entire housing from the mount to locate the O-ring and reseat it. This is done by rotating the entire housing counterclockwise. Once the polar axis finder scope is in the housing, tighten the three thumbscrews. These thumbscrews will be used later to align the finder with the mount’s R.A. axis.

Installing the Finder Scope

To place the finder scope in the finder scope bracket, first unthread the two black nylon screws until the screw ends are flush with the inside diameter of the bracket. Place the O-ring that comes on the base of the bracket over the body of the finder scope until it seats into the slot on the middle of the find- er scope. Slide the eyepiece end (narrow end) of the finder scope into the end of the bracket’s cylinder opposite the adjustment screws while pulling the chrome, spring-loaded tensioner on the bracket with your fingers (Figure 2b). Push the finder scope through the bracket until the O-ring seats just inside the front opening of the bracket cylinder. Now, release the tensioner and tighten the two black nylon screws a couple of turns each to secure the finder scope in place. Insert the base of the finder scope bracket into the dovetail slot on the top of the focuser. Lock the bracket into position by tightening the knurled thumbscrew on the dovetail slot.

Inserting the Eyepiece

Loosen the thumbscrew on the 1.25" eyepiece adapter (Figure 3) and insert the chrome barrel of the star diagonal into the adapter. Then, loosen the thumbscrews on the star diagonal and remove the small dust cap. Then insert the 25mm Sirius Plössl eyepiece into the focuser and secure it with the thumbscrews.

Your telescope is now completely assembled and should appear as shown in Figure 1.

3. Getting Started

Balancing the Telescope

To ensure smooth movement of the telescope on both axes of the equatorial mount, it is imperative that the optical tube is properly balanced. We will first balance the telescope with respect to the R.A. axis.

1.Keeping one hand on the telescope optical tube, loosen the R.A. lock lever. Make sure the Dec. lock lever 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).

2.Now loosen the counterweight lock knob and slide the weight along the shaft until it exactly counterbalances the telescope (Figure 4a). That’s the point at which the shaft remains horizontal even when you let go with both hands (Figure 4b).

3.Retighten the counterweight lock knob. The telescope is now balanced on the R.A. axis.

The telescope should be balanced in the Dec. axis already if you have properly centered the 1/4"-20 mounting block on the optical tube relative to the tube rings.

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