Bushnell 78.9565 manual Selecting an Eyepiece, Viewing Land-Based Objects, Aligning Finderscope

Selecting an Eyepiece:

1.You should always start viewing with the lowest power eyepiece, which in this case is the 20mm lens. Note: the base power of each eyepiece is determined by the focal length of the telescope objective lens, which for this model is 750 mm. A formula can be used to determine the power of each eyepiece: telescope OBJECTIVE lens focal length EYEPIECE focal length = MAGNIFICATION (e.g. Using the 20 mm lens, the calculation would look like this: 750 mm ÷ 20mm = 38x or 38 power.)

2.Included with this telescope is a Barlow lens. Barlow lenses are used to double or triple the power of your telescope. Place your Barlow between the focusing tube and the Penta Mirror. Note: The Penta Mirror

Assembly when used in conjunction with the Barlow Lens and Eyepiece as shown on diagram will

yield an effective doubling power of the magnification already achieved with the Barlow and Eyepiece configuration alone. The magnification calculation would look like this: 750 mm ÷ 20mm = 38 power. 38 power x 3=114 power. 38 x 3 x 2=228 power. (See Intended Configuration Diagram).

Focusing Telescope:

1.After selecting the desired eyepiece, aim main telescope tube at a land-based target at least 200 yards away (e.g. A telephone pole or building). Fully extend focusing tube by turning Rack and Pinion Focusing Mechanism (15).

2.While looking through selected eyepiece (in this case the 20 mm), slowly retract focusing tube by turning Rack and Pinion Focusing Mechanism until object comes into focus.

Viewing Land-Based Objects:

1.As described above, the Erecting Lens will correct the normally upside down and reversed image so that you can easily enjoy observing land-based objects through your telescope.

2.Simply insert the Erecting Lens into the focusing tube of the telescope followed by the penta mirror, then insert an eyepiece into the penta mirror. (See Intended Configuration Diagram).

3.Repeat focusing directions as described above except that you will be looking through the Erecting Lens and eyepiece instead of just the eyepiece.

Aligning Finderscope:

Look through main telescope tube at low power and establish a well-defined stationary target. Looking through red dot finderscope, alternate tightening each adjustment wheel (at rear and left side of finderscope) until the red dot of finderscope is precisely aligned and centered on the same object being viewed in main telescope tube. See finderscope page.

Now, objects located first with the Finderscope (18) will be centered in the field of view of the main telescope.

Balancing the Telescope

1.Arrange the telescope so that the telescope body is horizontal to the floor (latitude of 0°). Loosen the Right Ascension Lock (4). The telescope should now turn freely about the polar axis. Rotate the telescope about the polar axis so that the Counterweight Shaft (5) is parallel to the ground (horizontal).

2.Loosen the Counterweight Lock Screw (located on the counterweight), and slide the Counterweight (6) along the shaft until the telescope remains stationary without drifting rotationally about the polar axis. Tighten the Counterweight Lock Screw, locking the Counterweight into position.

3.Now balance the telescope about the Declination Axis. Loosen the Declination Lock Knob (3) and the Cradle Lock Knobs (fig. 3) so that the telescope can slide freely inside the Cradles. Slide the telescope up or down inside the rings until

Cradle (20)

Fig. 3