My telescope mount's azimuth base is slipping. How can I fix it?

BBC Sky at Night Magazine's Scope Doctor Steve Richards solves your practical astronomy ailments.

Vixen Mobile Porta Altazimuth Mount. Credit: Opticron
Published: March 29, 2020 at 3:24 pm
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I have a Sky-Watcher Skyliner 300P FlexTube Go-To telescope. Though I can hear the motor working, the azimuth base is slipping. Taking off the base and adjusting the bolts and worm gear makes no difference.

Steve says: "As you can hear the mount's motor working yet not making an unpleasant noise, it would be safe to assume that the meshing of the worm gear is not the cause of the slippage here. It’s more likely to be the slip clutch.


Both axes on the Skyliner 300P FlexTube Go-To mount have this slip clutch for safety, to protect the gears from damage in case the movement of the scope is impeded in any way.

It’s fairly basic in operation but can be adjusted if it does start to slip too easily.

To adjust the clutch on the azimuth axis, remove the four crosshead screws that keep the plastic cover in place on the rocker box base.

This will reveal the exposed motor and encoder, which is a circular black housing. If you look under the encoder housing, you will see three ‘washers’ and a 17mm AF self-locking hexagonal bolt.

Gently turn this bolt clockwise to tighten the clutch – just an eighth of a turn should suffice."


Email your astronomy queries to Steve at and they could get answered in a future issue of BBC Sky at Night Magazine.


Astronomer Steve Richards
Steve RichardsAstronomer and author

Steve Richards is a DIY astronomy expert and author of Making Every Photon Count: A Beginner’s Guide to Deep Sky Astrophotography.

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