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IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.

How to Balance ZWO AM3N, AM5N, and AM7: The Counterweight Guide

The ZWO AM-series mounts (AM3N, AM5N, and AM7) are strain-wave gear powerhouses. Unlike traditional mounts that require a "see-saw" balance, these mounts operate on a Counter-Torque principle. Whether you are using the portable AM3 or the high-capacity AM7, the rules for stability and tracking precision remain the same.

Why Balancing an AM-Series Mount is Different

On a standard German Equatorial Mount (GEM), you balance the telescope against the counterweight until they reach equilibrium. On a ZWO strain-wave mount:

  • Balance is Payload-Independent: The placement of your counterweight does not depend on how heavy your telescope is.
  • The Goal is Torque, Not Equilibrium: You are aiming for a specific mechanical "pressure" of 10 to 15 N·m to keep the gears engaged and the tripod stable.

The "Sweet Spot": 10–15 N·m

ZWO recommends the specific torque range of 10–15 N·m for two vital reasons:

  1. Preventing Tip-Over: These mounts are lightweight. A heavy telescope can shift the Center of Gravity (CoG) outside the tripod's legs. The counterweight pulls that CoG back to the center.
  2. Smoothing the Gears: Strain-wave gears use a flexible "flexspline." Providing a consistent 10–15 N·m of force ensures the gear teeth mesh perfectly, reducing microscopic flex and improving autoguiding responsiveness.

How to Calculate Counterweight Placement

To find the correct position (L) for your weight, use this simple formula:

10 N⋅m≤Mass (kg)×10×Distance (meters)≤15 N⋅m

Quick Reference Placement Table:

Counterweight Mass Allowable Distance (L) from Mount Center
5 kg (Max Recommended) 20 cm to 30 cm
3 kg 33 cm to 50 cm
2 kg 50 cm to 75 cm

Step-by-Step Installation

  1. Thread the Bar: Screw the counterweight shaft into the DEC axis. Ensure it is tight to prevent vibrations.
  2. Measure the Distance: Slide your weight onto the bar. Use a tape measure to ensure the center of the weight falls within the ranges listed above.
  3. Safety Bolt: Never operate without the "toe-saver" bolt screwed into the end of the shaft.
  4. The "Dry Run": Manually slew the mount to ensure the bar or weight doesn't strike your tripod or pier.

Summary for AM3, AM5N, and AM7 Users

If your telescope is light, you likely don't need a counterweight at all. However, if you are nearing the mount's "no-weight" capacity, adding a 2–5 kg weight in the 10–15 N·m zone will stabilize your tripod and deliver the smoothest possible tracking for long-exposure astrophotography.

Comments

Balasubramanyam CV - April 22, 2026

What about horizontal balancing of scope?

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