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keep an object centered in the field of view, just
lightly nudge the telescope in the proper direction.
This may take a little practice at first, but you’ll soon
get the hang of it.
4. The telescope should be placed on a relatively
level surface to allow proper operation. Each of
the three feet should be in firm contact and not
wobble. If you are in an area with particularly rough
or soft ground, it may be helpful to place the Mount
on a thick piece of plywood.
5. Part of the fun of using a Dobsonian type of
telescope is the challenge of hunting for objects
in the night sky. Invest in some simple star charts
and books that tell you how to locate objects using
a technique called “star hopping.” Once you begin
learning the star patterns and constellations, you’re
well on you way to finding many amazing sights.
6. If using heavy eyepieces or accessories, the
front of the optical tube may drift downward until
the additional weight. Use the altitude brake (19,
Fig. 1) to increase the friction on the altitude
bearing until the drift is gone. Don’t over tighten or
the optical tube will be too difficult to track objects
in the night sky.
CALCULATING MAGNIFICATION
The magnification, or power of a telescope is
determined by two factors: the focal length of the
eyepiece and the focal length of the telescope.
Your telescope is supplied with one eyepiece. The
focal length of the eyepiece, 26mm, is printed on
its side.
Telescope focal length is the distance that light
travels inside the telescope before reaching a
focus.
The focal length of the Dobsonian 10” = 1270mm
The focal length of the Dobsonian 12” = 1524mm
The focal length of the Dobsonian 16” = 1829mm
To change magnification, change eyepieces.
To calculate the magnification of a given eyepiece,
use this formula:
Power =
Telescope Focal Length
___________________
Eyepiece Focal Length
Example: Using the 26mm eyepiece supplied with
the 10” f/5 LightBridge Plus telescope, the power
is:
Power =
1270mm
______ = 49x (approx.)
26mm
The type of eyepiece, whether Modified
Achromatic, Plössl, or Super Plössl, has no effect
on magnification, but does have a bearing on such
optical characteristics as field of view, flatness of
field, and color correction.
Maximum practical magnification is about 50X per
inch of aperture. Generally, however, lower powers
produce higher image resolution. When unsteady
air conditions prevail (as witnessed by rapid
“twinkling” of the stars), extremely high powers
result in distorted magnification and observational
details are diminished by the use of excessive
power.
When beginning observations on a particular
object, always start with a low power eyepiece.
Center the object in the field of view. Sharply
focus the object. Then try using a higher power
eyepiece. If the image starts to become fuzzy when
you use higher magnification, back down to a lower
power. The atmosphere is not sufficiently steady to
support high powers. Keep in mind that a bright,
clearly resolved, but smaller image will show far
more detail than a dimmer, poorly resolved larger
image.
OBSERVING
Observe during the daytime: Try out your telescope
during the daytime at first. It is easier to learn how it
operates and how to observe when it is light.
Pick out an easy object to observe: A distant
mountain, a large tree, a lighthouse or skyscraper
make excellent targets. Point the optical tube so it
lines up with your object.
Use the red dot finder: If you have not done so, align
the red dot finder with the telescope’s eyepiece as
described earlier. Look through the finder until you
can see the object. It will be easier to locate an
object using the finder rather than locating with the
eyepiece. Line up the object with the finder’s red
dot.
Look through the eyepiece: Once you have the
object lined up in the finder, look through the
