Orion 9851 instruction manual a.b c.d, Focusing the Telescope

a.b.

c.d.

Figure 4a, 4b, 4c, 4d. Proper operation of the equatorial mount requires that the telescope tube be balanced on both the R.A. and Dec. axes. (a) With the R.A. lock knob 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. (c) With the Dec. lock knob released, loosen the tube ring lock clamps a few turns and slide the telescope forward or back in the tube rings. (d) When the tube is balanced about the Dec. axis, it will not move when you let go.

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 coun- terweight 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 of the telescope with both hands (Figure 4b).

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

4.To balance the telescope on the Dec. axis, first tighten the R.A. lock knob, with the counterweight shaft still in the horizontal position.

5.With one hand on the telescope optical tube, loosen the Dec. lock knob. The telescope should now be able to rotate freely about the Dec. axis. Loosen the tube ring clamps a few turns, until you can slide the telescope tube forward and back inside the rings (this can be aided by using a slight twisting motion on the optical tube while you push or pull on it) (Figure 4c).

6.Position the telescope so it remains horizontal when you carefully let go with both hands. This is the balance point (Figure 4d). Before clamping the rings tight again, rotate the telescope so the eyepiece is at a convenient angle for viewing. When you are actually observing with the tele- scope, you can adjust the eyepiece position by loosening the tube rings and rotating the optical tube.

7.Retighten the tube ring clamps.

The telescope is now balanced on both axes. Now when you loosen the lock knob on one or both axes and manually point the telescope, it should move without resistance and should not drift from where you point it.

Focusing the Telescope

Insert the low-power 25mm eyepiece into the focuser and secure with the thumb screws. Move the telescope so the front (open) end is pointing in the general direction of an object at least 1/4-mile away. Now, with your fingers, slowly rotate one of the focusing knobs until the object comes into sharp focus. Go a little bit beyond sharp focus until the image just starts to blur again, then reverse the rotation of the knob, just to make sure you’ve hit the exact focus point.

If you have trouble focusing, rotate the focus knob so the drawtube is in as far as it will go. Now look through the eye-

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