My mount ponting (GOTO) accuracy 6 arcmin. Tracking error with good polar aligment (periodic error) +-15 arcsec without guiding. With autoguiding small amount error remain (0,5-2 arcsec). SX110 camera has 10x optical zoom. Maximal zoom not used, average zoom = 6 arcsec/ pixel resolution. Final resolution better. Some pixels dirthering required on final image. Guiding speeds 0.125, 0.5, 0.5, 1x sideral rate support on my mount. I use guider scope with cheap webcam with netbook.
I not know, astromkam support external autuguider or has own? Freeware autoguider available with dirthering support with external camera control software (phd guiding2, metaguide, ...). Guide important, periodic error too high. Some, not chdk compatible camera control software has function to send dirthering info for external autoguide program.
I have second camera (a590) with chdk. Not tested with astrokam. This camera small, good for digiscoping with large telescope. Digiscoping adapter not completed yet. This setup has a very high resolution, but seeing limited.