Counterweight

The weight fixed on a bar opposite the tube on a German equatorial mount. Slide it until the polar axis stays still when unlocked. Good balance spares the motors and improves tracking.

Related terms

Equatorial mount: A mount with one axis (the right ascension, or polar, axis) parallel to the Earth’s axis of rotation. Once polar aligned, turning that single axis follows the stars, by hand or with a motor. The “German” type, with counterweights, is the most common.
Tracking: The motion that cancels the Earth’s rotation to keep an object in view. At the sidereal rate the mount makes one turn in 23 h 56 min, about 15 arcseconds per second. At 200× with a 50° eyepiece, an untracked star near the celestial equator crosses the field in about a minute.

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