Bushnell Exploring the Universe Instruction Manual

Exploring the Universe

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. A formula
can be used to determine the power of each eyepiece:
telescope objective lens focal length divided by
eyepiece focal length = magnification. (e.g. Using the
20 mm lens, a sample calculation would look like this:
900 mm / 20 mm = 45 power. Telescope models will
vary in focal length.)

2. Included with this telescope is a Barlow lens. The
Barlow lens is used to triple or double the power of your
telescope. You will want to get comfortable with the
other lens before using the Barlow lens. You will place
the Barlow lens between the focusing tube and the
eyepiece.

Using the example above, your 3X Barlow lens would

tube

eyepiece

give you a total power of 135.
(45 X 3 = 135 power)

Focusing the Telescope

1. Before you focus the telescope be sure to take the dust
caps off the front of the main tube. There are two caps: a
small cap, which fits inside the large cap that covers the
entire front of the main tube. The large cap is also called
the moon filter.

2. After selecting the desired eyepiece, aim the main
telescope tube at a land-based object that is at least 300
to 400 yards away. A telephone pole, stop sign or a
building would be a good choice. Don’t be surprised

the object will appear upside down.

3. Fully extend the focusing tube by turning the

Rack and Pinion Focusing Mechanism.

Focusing Mechanism

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

Aligning the Finderscope

This process must be done before you start viewing the
night sky.

1. Look through the Main Telescope Tube and establish a
well-defined target. In a reflector telescope the image
will appear upside down.