---
title: "Diagnosing and reducing mechanical play in the mount"
canonical: https://stackingstarlight.com/troubleshooting/mount-backlash
description: "If tracking hesitates or jumps right after the mount reverses direction — a short lag before the star catches up, then a small jump — this is mechanical play (backlash) in the gear train. Here's how to confirm it and reduce it, and how to tell it apart from the other things that look similar."
---

# Diagnosing and reducing mechanical play in the mount

> If tracking hesitates or jumps right after the mount reverses direction — a short lag before the star catches up, then a small jump — this is mechanical play (backlash) in the gear train. Here's how to confirm it and reduce it, and how to tell it apart from the other things that look similar.

## 1. Confirm it's reversal play, not something else

- **Lag/jump only on direction reversal** (most visible in DEC) → backlash. Keep reading.
- **Slow steady drift in one axis** → polar alignment or periodic error, an autoguiding/PA issue, not
  backlash. See [stabilizing autoguiding](/troubleshooting/guiding-phd2).
- **Random jumps unrelated to reversals** → balance, wind, or snagged cables.

## 2. Diagnose

Use your guiding software's **backlash measurement** (it drives the axis one way, reverses, and times
how long before motion resumes). Read the **guide log**: backlash shows as a flat dead zone after a
commanded reversal. Note which axis and how many milliseconds/pixels of dead travel.

## 3. Reduce it

- **Mechanical first:** adjust the worm/gear mesh per your mount's procedure so play is minimal
  *without* binding. Over-tightening causes stiction, which is worse than a little backlash.
- **Balance slightly off in DEC** so the gear is always loaded on one face — this hides residual play.
- **Software backlash compensation** as a last layer (small values only; too much causes overshoot).
- **Polar alignment** touch-up so guiding makes fewer reversals in the first place.

## 4. Verify

Re-run the backlash measurement and watch a few reversals in the guide graph — the dead zone should
shrink. Confirm over a real sub, not just the assistant.

## When it isn't the mount

If corrections oscillate or overshoot continuously (not just at reversals), that's a guiding-tuning
problem → [stabilizing autoguiding](/troubleshooting/guiding-phd2).

---

How the mount works: [what an equatorial mount does](/equipment/eq-mount).
Shopping because play is too large to tune out? [Choosing a mount for your payload](/buy/mount).

---

Source: [https://stackingstarlight.com/troubleshooting/mount-backlash](https://stackingstarlight.com/troubleshooting/mount-backlash) · Part of [Stacking Starlight](https://stackingstarlight.com) by Michael Kalika.

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