Setting Up And Using The Equatorial Mount - Orion STARMAX 90 EQ Instruction Manual

2. Now loosen the counterweight lock knob and slide the
weight along the shaft until it exactly counterbalances the tele‑
scope (Figure 3a). That's the point at which the shaft remains
horizontal even when you let go of the telescope with both
hands (Figure 3b).
3. Retighten the counterweight lock knob.
The telescope is now balanced on the R.A. axis. It is not nec‑
essary to balance the telescope on the Dec. axis, since the
optical tube's mounting block is positioned so that the tele‑
scope will automatically be balanced on that axis. Now when
you loosen the lock knob on one or both axes of motion and
manually point the telescope, it should move without resis‑
tance and should not drift from where you point it.
Focusing the telescope
Point the telescope so the front end is aimed in the general
direction of an object at least 1/4‑mile away. Now, with your
fingers, slowly rotate the focusing knob until the object comes
into sharp focus. Go a little bit beyond sharp focus until the
image just starts to blur again, then reverse the rotation of the
knob, just to make sure you've hit the exact focus point.
If you have trouble focusing, rotate the focus knob counter‑
clockwise as far as it will go. Now look through the eyepiece
while slowly rotating the focus knob clockwise. 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. In order to do this, your eyepiece must
have enough "eye relief" to allow you to see the entire field of
view with glasses on. 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 the glasses do restrict the field of view, you may be
able to observe with your glasses off by just refocusing the
telescope 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
The finder scope (Figure 4) must be aligned accurately with
the telescope for proper use. To align it, aim the main tele‑
scope 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 eye‑
piece.
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 three black nylon finder scope
6
Nylon thumbscrew
O‑Ring
(not shown)
Objective
lens
Finder scope
Figure 4: The 6x20 Correct‑Image finder scope and bracket
alignment thumbscrews will be needed to get the finder scope
roughly parallel to the main tube.
Note: The image in the telescope's eyepiece will appear
inverted from left‑to‑right (mirror reversed), which is normal
for telescopes that utilize a star diagonal. The image in the
finder scope is oriented the same as the naked eye.
Use the three nylon thumbscrews to center the object on the
crosshairs of the finder scope. Then look again into the tele‑
scope's eyepiece and see if the object is still centered there
as well. If it isn't, repeat the entire process, making sure not
to move the main telescope while adjusting the alignment of
the finderscope.
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.
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. Turn the end of the finder scope with the
rubber eyeguard clockwise or counter‑clockwise as needed
to focus the finder scope on a distant object (1/4 mile away
or more). Precise focusing will be achieved by focusing the
finder scope on a bright star.
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 rotation
(from west to east). An equatorial mount (Figure 2) is designed
Rubber
eyeguard
Nylon
thumbscrew
Finder scope
bracket