thanks for the replies,   I've tried the PHD comet tracking routine - w/o using Kstars - and found it difficult to get good guiding on the object.  Especially with comets there may or not be a too big or too bright or too dim a 'fuzz ball' to find a centroid or just moving in one axes too fast or erratically.  Stacking  is also possible but also has variable results.  Am hoping to develop some spectroscopy capability and so tracking at the rate of the object will be necessary to 'fix' its position.  That also works better for imaging 'close flyby' NEO asteroids.  So I don't have to 'learn by trial and error' -   In my 2nd post I was hoping someone could comment whether I have the right order to input the rates in the Track Rates Indi panel?