The method I have been talking about is described here as a feature request:
It is written as a method for centering that should solve the problem I have - and the problem many other people have who find that the synch/slew approach gets close and then stops converging. It is stuck very repeatably at some location from the target.
The approach described should work whether you do a sync after each solve or not.
In my case the mount model could be perfect - but if the mount is told to go to ra/dec and it lands slightly away from it - the ra/dec values do reflect the true values - but they are off from where it was told to go. As a result syncing has no effect - because it is already exactly where it thinks it is - but it is not where it was told to go. This is not backlash - it is overshoot or undershoot while dead reckoning. If it were backlash, the encoders would have the correct values, but the pointing would be away from that location.
Syncing is bad for two reasons: it alters the mount model, which for some mounts is problematic, and it may make pointing in other parts of the sky worse. But it is good because it will improve goto accuracy in a region of the sky - and it will improve the ra/dec values reported by the mount and put in the fits header. But a plate solve should insert much more accurate values anyway - if each image is solved.
So I can see the merits of having an option to sync or not. But it would only slightly alter the logic of having sgp track the error when going to a target and compensate for it.
Unless an approach like this is taken - my pointing accuracy will never improve - and people with particular sync methods in their mounts will report problems centering.
If you simply want to support high end mounts that can point reliably - there is no need for centering at all. Just require that the mount point accurately on a single slew. In this case I think there is a simple approach that would work for everyone - with a few lines of code. And for most people - it would have advantages in speed and simplicity.
Frank