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.
- 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.
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How the mount works: what an equatorial mount does.
Shopping because play is too large to tune out? Choosing a mount for your payload.
Common questions
Why does tracking lag or jump when my mount reverses direction?
A short lag then a small jump on direction reversal (most visible in DEC) is mechanical play — backlash — in the gear train, not guiding oscillation or polar-alignment drift.
How do I reduce mount backlash?
Measure it with your guiding software, adjust the worm/gear mesh without over-tightening, bias DEC balance to load one gear face, and add small software backlash compensation as a last layer.