Bushnell 78-4500 Telescope Use Selecting An Eyepiece, Focusing Telescope, Aligning Finderscope

TELESCOPE USE

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 element, which for this model is 900 mm. A formula can be used to determine the power of each eyepiece: telescope OBJECTIVE mirror 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 81x or 81 power. (27 x 3 = 81x or 81 power)

3.Other accessories available include a 9mm eyepiece (model #78-0101) and a standard camera adapter (model #78-0104) for photographing the night sky.

FOCUSING TELESCOPE:

1.After inserting the eyepiece, aim the 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 & Pinion Focusing Mechanism (1)

2.While looking through selected eyepiece (in this case the 20 mm), slowly retract focusing tube by turning Rack & Pinion Focusing Mechanism (1) until object comes into focus.

ALIGNING FINDERSCOPE:

1.Look through low-power 1.25" format eyepiece (8) and establish a well-defined target (see focusing telescope section).

2.Looking through Finderscope (7), alternate tightening each Finderscope Adjustment Screw surrounding the Finderscope (7) in the Finderscope Mount until crosshairs of Finderscope (7) are precisely centered on the same object already centered in Main Telescope Tube's field of view as seen through the 1.25" Format Eyepiece (8).

3.Now, objects located first with the Finderscope (7) will be centered in the field of view of the main telescope as seen through the 1.25" Format Eyepiece (8).

Enjoying Your New Telescope

1.First determine your targeted object. Any bright object in the night sky is a good starting point. One of the favorite starting points in astronomy is the moon. This is an object sure to please any budding astronomer or experienced veteran. When you have developed proficiency at this level, other objects become good targets. Saturn, Mars, Jupiter, and Venus are good second steps to take.

2.The first thing you need to do after assembling the telescope as planned is center the desired object in the finderscope's cross hairs. Provided you did a reasonable job aligning the finderscope, a quick look through the main telescope tube at low power should reveal the same image. With the lowest power eyepiece (the one with the largest number printed on it) you should be able to focus the same image that you saw through the finderscope. Avoid the temptation to move directly to the highest power. The low power eyepiece will give you a wider field of view, and brighter image--thus making it very easy to find your target object.