Error on Centering has grown significantly

Just another quick question - as a matter of interest: what accuracy are you looking for? I tell SGP to get me within 20 pixels. I feel that this is close enough, given that I will be dithering between frames all night anyway. SGP does this with no problem with one or sometimes two moves after the initial slew.
Is there any chance that you are aiming for Zero?..... which is indeed asking a lot of some (or perhaps most) mounts.