Salvador- I think I can answer that one. First is that exposure times are so short that rate of motion involved isn't of consequence (in terms of a daylight or well illuminated situation).. and in the case of a telescope, since the earth itself is in continuous motion and you are trying to compensate for that during a timed long exposure. If you take a 30 second exposure of the sky at night, the stars are not points.. they become lines (because the camera is in motion relative to the star) Everything gets "smeared". However, if you have a motorized system compensating for the motion, you can keep the camera trained on a point for long enough to do extended exposures.. and ideally the compensation (like the earth's rotation) is a continuous smooth motion and not discrete "detents" every few degrees. This combined with Image Stacking can make for some awesome astrophotography.
That's my educated guess, anyway 