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Figure 15. The StarSeeker IV mount is powered by eight user-
supplied AA batteries, which are installed in the mount arm.
and barrel diameter. The focal length of each eyepiece is
typically printed on the eyepiece body. The two eyepieces
included with your telescope have a 1.25" barrel diameter. One
has a focal length of 23mm and the other, 10mm. The longer
the focal length (i.e., the larger the number), the lower the eye-
piece power or magnification; and the shorter the focal length
(i.e., the smaller the number), the higher the magnification.
Generally, low or moderate power will produce the sharpest
images when viewing.
You can change the magnifying power of your telescope just
by changing the eyepiece (ocular). To determine the magnifi-
cation of your telescope, simply divide the focal length of the
telescope by the focal length of the eyepiece used.
Telescope Focal Length (mm)
Eyepiece Focal Length (mm)
For example, the StarSeeker IV 114mm reflector has a focal
length of 500mm, which when used with the supplied 23mm
eyepiece yields 22x magnification:
The magnification provided by the 10mm eyepiece is:
Although the power can be varied, each instrument under
average skies has a limit to the highest useful magnification
that can be achieved. The general rule is 2x per millimeter of
aperture is as high as you can reasonably go (with optional
eyepiece and possibly a Barlow lens). For example, the
StarSeeker IV 114mm reflector has a primary mirror that's
114mm in diameter. So 114mm times 2x per millimeter = 114
= Magnification
500mm
= 22x
23mm
500mm
= 50x
10mm
x 2 = 228. Thus, 228x is the highest useful magnification one
can normally achieve under ideal seeing conditions with this
telescope. (Trying to go higher would likely just result in dim,
blurry images.) Although this is the maximum useful magnifi-
cation, most observing will yield best results at lower powers.
Focusing
To focus, if you have a StarSeeker IV Newtonian reflector or
refractor telescope, simply turn either of the two focus wheels
on the focuser until the image looks sharp. For the Maksutov-
Cassegrain models, the focus knob resides to the right of the
visual back, or accessory adapter. Make sure you're aimed at
something far off in the distance. If you don't see an image at
first, keep turning the focus knob in one direction while looking
through the eyepiece; if you reach the end of the focuser travel
start turning the focus knob in the other direction. Eventually,
you should see the object you're aimed at come into view. After
going just past the focus point in one direction, and then in
the other direction, you will then be able to home in on the
exact focus point using progressively smaller turns of the focus
knobs.
Image Orientation
For astronomical telescopes, the image orientation in the eye-
piece will usually be different from the orientation you would
see with the naked eye. Refractor and Maksutov-Cassegrain
telescopes used with a standard 90-degree "star diagonal" will
provide a right-side-up but backwards (mirror-reversed) image.
For reflector telescopes the image in the eyepiece will appear
Figure 16 The electronic ports for the hand controller and
an optional 12V DC battery are located at the base of the
mount arm. The SNAP port allows control of a DSLR camera
when used with proper cable.
9
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