7
piece while slowly rotating the focus knob in the opposite
direction. You should soon see the point at which focus is
reached.
Do You Wear Eyeglasses?
If you wear eyeglasses, you may be able to keep them on
while you observe, if your eyepieces have enough “eye relief”
to allow you to see the whole field of view. You can try this
by looking through the eyepiece first with your glasses on
and then with them off, and see if the glasses restrict the
view to only a portion of the full field. If they do, you can eas-
ily observe with your glasses off by just refocusing the tele-
scope the needed amount.
If your eyes are astigmatic, images will probably appear the
best with glasses on. This is because a telescope’s focuser
can accommodate for nearsightedness or farsightedness,
but not astigmatism. If you have to wear your glasses while
observing and cannot see the entire field of view, you may
want to purchase additional eyepieces that have longer eye
relief.
Aligning the Finder Scope
Now, look in the finder scope. Is the object visible? Ideally,
it will be somewhere in the finder’s field of view. If it is not,
some coarse adjustments of the two black nylon finder scope
alignment thumb screws will be needed to get the finder
scope roughly parallel to the main tube.
The finder scope must be aligned accurately with the tele-
scope for proper use. To align it, aim the main telescope
in the general direction of an object at least 1/4-mile away,
such as the top of a telephone pole, a chimney, etc. Do this
by first loosening the R.A. and Dec. lock knobs. Position the
telescope so the object appears in the eyepiece’s field of
view and then retighten the R.A. and Dec. lock knobs. Use
the slow-motion control cables to center the object in the
eyepiece.
By loosening or tightening the alignment thumb screws, you
change the line of sight of the finder scope. Continue making
adjustments to the alignment thumb screws until the image in
both the finder scope and the telescope’s eyepiece is exactly
centered. Check the alignment by moving the telescope to
another object and fixing the finder scope’s crosshairs on
the exact point you want to look at. Then look through the
telescope’s eyepiece to see if that point is centered in the
field of view. If it is, the job is done. If not, make the neces-
sary adjustments until the two images match up.
NOTE: The image in both the finder scope and the main
telescope will appear upside-down (rotated 180°). This is
normal for finder scopes and reflector telescopes (see
Figure 5).
The finder scope alignment needs to be checked before
every observing session. This can easily be done at night,
before viewing through the telescope. Choose any bright
star or planet, center the object in the telescope eyepiece,
and then adjust the finder scope’s alignment screws until the
star or planet is also centered on the finder’s crosshairs. The
finder scope is an invaluable tool for locating objects in the
night sky; its usage for this purpose will be discussed later,
in detail.
When transporting the telescope, we recommend removing
the finder scope and bracket from the tube. This is done by
simply loosening the thumb screw on the dovetail slot. Store
the finder scope and bracket in an appropriate eyepiece/
accessory case.
Focusing the Finder Scope
If, when looking through the finder scope, the images appear
somewhat out of focus, you will need to refocus the finder
scope for your eyes. Loosen the lock ring located behind
the objective lens cell on the body of the finder scope (see
Figure 3a). Back the lock ring off by a few turns, for now.
Refocus the finder scope on a distant object by threading the
objective lens cell in or out on the finder scope body. Precise
focusing will be achieved by focusing the finder scope on a
bright star. Once the image appears sharp, retighten the lock
ring behind the objective lens cell. The finder scope’s focus
should not need to be adjusted again.
5. Setting up and using
the Equatorial Mount
When you look at the night sky, you no doubt have noticed
that the stars appear to move slowly from east to west over
time. That apparent motion is caused by the Earth’s rota-
tion (from west to east). An equatorial mount (Figure 2) is
designed to compensate for that motion, allowing you to
easily “track” the movement of astronomical objects, thereby
keeping them from drifting out of the telescope’s field of view
while you’re observing.
This is accomplished by slowly rotating the telescope on its
right ascension axis, using only the R.A. slow-motion cable.
But first the R.A. axis of the mount must be aligned with
Naked-eye view
View through finder scope and telescope
Figure 5.
The view through a standard finder scope and
reflector telescope is upside down (rotated 180°). This is true for the
SpaceProbe 130mm and its finder scope as well.
