Anyone see this sort wild oscillation on the DEC axis and know what might cause it? I've already done the obvious stuff like re-checking polar alignment, checking balance, checking for cable snags, and there's no wind.

My AVX is not overloaded; there's not even 4kg on it - Askar V 60mm (2.8kg) , ZWO EAF (0.3kg), ASI533 (0.5kg) - and the mount is rated for about 15kg. Control is via a StellarmateX, guiding is using the ekos internal guider. This also isn't a constant thing. Some nights I don't see the oscillation at all and some nights I do. I'm not using the GPG guider which only operates on the RA axis anyway, nor am I using any form of PEC.

This happens no matter what the aggressiveness/gain, maximum move, and exposure settings are. Less aggressiveness and longer exposure just means it takes longer to complete a cycle.

Possibly a red herring, but one thing I've noticed is the drift plot flashing white for a brief moment, as if there is some sort of refresh delay somewhere. I don't see any thing in dmesg to indicate USB errors, nor indications of swapping in top.

-C

IIRC, flashing white is when it fails to detect any stars. This can lead to bad guiding of course.

Looks like Dec is swapping sides continually and with backlash its just overshooting before recovering .... and then overshooting again.

I don't have any experience with the AVX mount but can you remove the backlash? If not, you could try balancing off-centre in DEC so the DEC is continually in motion in the same direction. If the DEC direction doesn't change that should eliminate the backlash. I suppose an alternative is to deliberately mis- Polar align in Dec so again guiding will continually drive DEC in 1-direction to avoid backlash.