In the example, the focal length is 768 mm and the width of a pixel is 17 microns (0.017 mm), so for this particular system, $pixel = 4.57 arc-seconds .
In addition to any periodic error present, the tracking data will almost certainly contain an offset value, x0, a rate of change, v, and an acceleration, a, or the rate of change of the rate of change. The rate of change is probably an error in the basic tracking rate, and the acceleration will probably be caused by atmospheric refraction changing the apparent motion of the star. By trial and error, you can plug in different values for the offset, rate error, and acceleration and plot the corrected position of the star, x, as a function of time:
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