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BALANCING THE TELESCOPE
To achieve the best performance from your mount, your telescope should be well-balanced. This is more important for
imaging setups than for visual setups since greater precision is required for guiding. Those who are setting up for visual
use or casual imaging need only be “adequately” balanced, as the mount’s drive system is very robust.
Common sense dictates that you want to begin the balancing procedure with your setup counterweight heavy so that
the scope does not suddenly leap from your hands and spin around into the pier. As long as the counterweight is down,
sudden movements of the Dec. axis cannot cause a damaging mishap. You will want to perform the balancing with the
scope set up exactly as it will be used. Eyepieces, diagonals, finder scopes, cameras, guiders, etc. should all be in place
before you begin.
Preliminary Balancing
1. With the counterweight shaft down and the scope pointing toward the pole (Park 3), loosen the Dec. clutch knobs
(about 3 to 4 full turns) and feel which way the scope’s weight is offset. Placing a hand on each end of the scope and
lifting back and forth will give you a good feel for balance. Slide the scope (in its rings or via the dovetail) until it feels
balanced, then point the scope to the north again and tighten the clutches.
2. Next, loosen the R.A. clutch knobs (about 2 to 3 full turns) and, while holding the counterweight shaft, move the axis
into a horizontal orientation. You will probably need to rotate the Dec. axis a bit so that it also assumes a horizontal
orientation. Place a hand at the end of the shaft and on the scope and, lifting back and forth, make counterweight
adjustments to equalize the balance as best possible.
This degree of balancing will be sufficient for those who wish to have some fun doing visual observing with family and
friends. If you are planning to do long-exposure, deep-sky imaging, then you’ll want to refine the balance. The steps
below will walk you through precision balancing.
Precision Balancing
Again, begin in Park 3. Remember that dangling cables will dramatically
change balance and create guiding problems, so you’ll want to be sure
that all cables are carefully secured and not dragging before you proceed
with balancing. Ensure that your focuser is in its focused position, the
dew shield extended and the dust cap removed. The following three
recommendations will increase guiding performance.
1. Slightly
offset balance to the counterweight side of the R.A. axis.
When the axis is perfectly balanced horizontally, then offset the weight
just enough to start motion
slightly
downward on the counterweight
side.
2. Slightly
offset balance to the camera side of the Dec. axis. When
the axis is perfectly balanced horizontally, then offset the scope just
enough to start motion
slightly
downward on the camera end.
3. The counterweights should ride high on the counterweight shaft. It is
best to add counterweights and slide them to the top of the shaft with
the heaviest at the top and then use the smallest weight to perform
the precision balancing. The reason for this is called “Inertial Moment
Arm”. Sliding less weight down the shaft will balance the scope, but
will greatly increase the moment arm force; that is to say, it will require
a much greater torque to start the axis rotating. (Think of a tightrope
walker using a long rod to stabilize his balance.) This is a very important consideration when you are trying to do pre-
cise guiding.
See illustration at right.
Disengaging the Worm and Worm Wheel
The new motor / gearbox design allows complete disengagement of the worm from the worm wheel allowing the
axis to turn freely for careful balancing.
It is important to begin with the scope approximately balanced since it will be
free to abruptly spin when the gears are disengaged. You definitely do not want the scope to yank from your hands and
crash into the pier! Important: Start this process in the safe Park 3 position - dangerous swings are avoided.
On the following page is a pictorial sequence that shows how to disengage the gears. It is as easy as flipping a lever!
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