Unlike a fork-mounted telescope, a German equatorial mount must be balanced
every time it is set up, whether for visual use or photography. Once you
have balanced the telescope a few times, this will become second nature.
Proper balance causes less wear on drive motors and allows the telescope to
track more accurately. In our experience, most tracking errors are caused
by an improperly balanced telescope. Learning to balance a telescope is
easy and can be an essential technique for many applications.
First, we will look at how to balance a telescope, then discuss the ideas
behind balance so you can better understand it.
Click Here for Quick Balance Reference
For more specific details, read the section below, then print out the above
Quick Reference to have with you in the field.
Balancing a German-Equatorial-Mounted Telescope
It is very important to balance the telescope tube (declination axis) first!
The most common balancing error is to reverse these steps. See the section at the bottom of this page for details why
this procedure is critical.
1) Begin by rotating the telescope and
counterweight bar so both are parallel to the ground, as shown below.
Carefully release the clutch holding the optical tube (declination) axis in
place and see if the telescope is front-heavy or rear-heavy.
Above: Push the telescope gently up and down to determine if it is
front- or back-heavy
2) Rotate the telescope so that it is directly
above the mount and aimed north. The telescope can now be slid forward or
backward to achieve proper balance.
Above: If the telescope is front-heavy slide the tube rearward on the mount. If the scope is
rear-heavy, slide the tube forward on the mount.
3) Bring the telescope and counterweight bar
back over into the horizontal position. Carefully release the clutch
holding the counterweight bar (right ascension) axis and see if the setup is
telescope- or counterweight-heavy.
Above: Return the telescope to the horizontal position once
balanced in declination. If the telescope is heavy toward the optical
tube, slide the counterweight down the shaft away from the scope. If the
telescope is heavy toward the counterweight, slide the weight up the shaft
toward the scope.
Why do you have to balance a German equatorial mount's
optical tube first? The reason lies in the position of the center of
gravity. If you do not balance the optical tube first, the center of mass of the tube is offset,
meaning the position of the counterweights on the shaft will be
incorrect. Even if the telescope seems balanced in one position, when
pointed to another area of the sky it may not be balanced.
If the telescope tube is not balanced first, then the
center of gravity (CG) of the system is not along the counterweight shaft
axis. This will cause the counterweight to be placed too close to
Balancing the optical tube first places the center of
gravity in the correct position. Now the counterweight will be in
the right place when the telescope is balanced in right ascension and the
entire system has been properly dynamically balanced.