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Mexican Bob

Celestron CG5 Advanced GT mount

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Hi. I’m quite new to astronomy and a GEM . Bought a second hand CG5 without proper knowledge of what I should have been looking for. I think that I have a problem with Dec axis travel. I’ll try to explain but please bare with me if I’m not making total sense. RA axis travel in both directions is good ( in smoothness and speed ).So is the Dec axis travel going clockwise, but anti-clockwise, the motor is slow and sounds laboured. I’ve replaced the motor in case it was that ,but the problem persists. Also when I release the direction button, the motor continues to slew for 2 or 3 seconds. Has anyone had a similar problem or has anyone any ideas how I can fix this? 

Thanks in advance 

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Ola Bob !

Does the dec labour without the OTA?

If it doesn't labour then it sounds like OTA balance - in one direction the weight is aiding the motor, in the other it's  overloading the motor.

If it's the same witthout the OTA then i would check the gear mesh.

I'm sure I've seen mention of continued motor operation before but cant remember the details....


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Hi Micheal. 

Thanks for your reply. Yes the motor does still labour without the OTA. When I replaced the motor,before assembling l held the gear with my finger and thumb then ran the motor. Clockwise, I couldn’t stop the motor but anti-clockwise it was quite easy to stop it. Because the original motor did this also ,I thought that maybe this was normal and that I’d replaced it for nothing. (Expensive mistake. But at least I have a spare motor). Anyway when I’ve fitted it ,the problem is still there. Hence this post. I’ll check the gear mesh and try and find any articles on the continued motor operation.. Do you think it might have anything to do with the small circuit board on the Dec motor side of the mount.?

Thanks for the suggestions Micheal..

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If you tested the new motor before installing and found it too behaved strangely, then the gear mesh is not the cause.

Can you check the volts to the motor in each direction with a multimeter?

Assuming you tested it off the mount but connected to the electronics, and considering  the slew overrun, its beginning to sound like a motor control board issue.


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