I wonder if I have a problem with my mount, what I am seeing during autoguiding is a large number of spikes on the RA trace. I thought it might be seeing/centroiding error but the same issue is not present on the DE trace (see image).
The size of the problem is about +/- 2" and it does lead to out of round stars sometimes.
The mount is a Losmandy G11G and it is not overloaded (carries an ED127 and a WO66SD). I have offset the balance so the mount is heavy on the E side so it should not be backlash.
If this is drive based noise where do I start looking - gearbox, worm? The mount is about 2 years old.