This image was taken with a modifided Canon 40D using a Canon 200mm lens. It is a 20min exposure at ISO400@f4. The camera was mounted piggy back on top of the CGE800 (on a dovetail see picture below). The period of the CGE worms is roughly 8min, so 20min corresponds to ca 2,5 worm periods - which is also confirmed in the sine wave star trails (the period is roughly 2,5 there).

The image scale of the Canon 40D with the 200mm lens is 5.9 arcsec/pix. Enlarging the image above one can see that the amplitude of the "sine wave" is roughly +/- 2.5pixels corresponding to a PE of ca +/- 15 arcsec (no PEC).

More PE analysis can be found here. A scetch of the internals of the CGE gear box (including images on what is what) can be found here.