Bushnell 78-9519 manual Selecting an Eyepiece, Focusing Telescope, Aligning Finderscope

Astronomical telescopes are designed in such a way that the image you will see appear will be UPSIDE DOWN and REVERSED, this is acceptable for viewing celestial bodies. For land-based viewing an “Erector Lens” is used to properly re-orient the image.

Selecting an Eyepiece:

1.You should always start viewing with the lowest power eyepiece, which in this case is the 20 mm lens. Note: the base power of each eyepiece is determined by the focal length of the telescope objective lens, which for this model is 900 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: 900 mm ÷ 20mm = 45x or 45 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 eyepiece. Using the example above, your 3x Barlow lens would give you a total power of 135x or 135 power. (45 x 3 = 135x or 135 power)

3.Also included with this telescope is an Erecting lens. The Erecting lens is used to view land-based objects where the correct image orientation is important. The Erecting lens re-orients the telescope image so that the image you are viewing is properly oriented. Place your Erecting lens between the focusing

tube and the eyepiece (fig. c). It is not recommended to use the Diagonal Mirror (16) with the Erecting lens. The Diagonal Mirror will make the erected image appear to be “flipped” depending on the orientation of the diagonal mirror- relative to the telescope.

Barlow or Erecting Lens

17

15

Focusing Telescope:

1.After selecting the desired tube at a land-based

(e.g. A telephone pole or building). Fully

Mechanism (15).

fig. c

eyepiece, aim main telescope target at least 200 yards away extend focusing tube by turning Rack and Pinion Focusing

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.

Aligning Finderscope:

1.Look through Main Telescope Tube (2) and establish a well-defined target. (see focusing telescope section) Tighten the Altitude Lock Knob (7) and Azimuth Lock Knob (8) so that telescope’s aim is not disturbed.

2.Looking through Finderscope (20), alternate tightening each Finderscope Adjustment Screw (19) until crosshairs of Finderscope are precisely centered on the same object already centered in main telescope tube's field of view.

3.Now, objects located first with the Finderscope (20) will be centered in the field of view of the main telescope.

Never Look Directly At The Sun With Your Telescope

Permanent Damage To Your Eyes May Occur