Orion 120 EQ instruction manual Balancing the Telescope

12.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 finder scope. Slide the eyepiece end (narrow end) of the finder scope into the end of the bracket’s cylin- der that does not have the adjustment screws while pulling the chrome, spring-loaded tensioner on the bracket with your fingers. 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.

13.Insert the base of the finder scope bracket into the dove- tail slot on the top of the focuser housing. Lock the bracket into position by tightening the knurled setscrew on the dovetail slot.

14.Remove the cover cap on the end of the focuser. Insert the chrome barrel of the star diagonal into the focuser and secure with the thumbscrew on the drawtube.

15.Then insert an eyepiece into the star diagonal and secure it in place with the thumbscrews on the diagonal. (Always loosen the thumbscrews before rotating or removing the diagonal or an eyepiece.)

16.Remove the objective lens dust cover and slide the metal lens shade over the front of the objective lens cell. The end of the lens shade with the 3 felt tabs should seat directly on the lens cell.

17.Install the polar axis finder scope into its housing inside the R.A. axis of the equatorial mount (Figure 3). First loosen the three setscrews on the housing, which is locat- ed at the rear of the R.A. axis. Remove the rubber O-ring from the finder and seat it in the groove that is just inside the housing’s opening. Insert the front end of the polar finder (the end without the eyeguard) into the housing and through the O-ring 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 O-ring from becom- ing 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 setscrews on the housing. These setscrews will be used later to align the finder with the mount’s R.A. axis. Now thread the housing assembly back into the mount (Figure 4).

The AstroView 120 is now assembled and should appear as pictured in Figure 1.

			Setscrew
Date circle				Pointer
Ring of housing	R.A.	setting circle
		Polar scope
containing time
	alignment screw
meridian indicator
mark			Polar axis
		finder scope

Figure 3. The polar axis finder scope is shown here installed in the right ascension (R.A.) housing of the mount.

Figure 4. You may find it easier to install the polar axis finder scope by unthreading the rear part of the R.A. housing, inserting the finder in it, then rethreading the assembly back on the mount.

3. 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, then the Dec. 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).

5