It looks like my imaging CCD is off-axis. Is that true?

No.  The imaging CCD is centered on the optical axis.

 

The reason it looks off-axis is because we moved the window 0.050 inches off-axis towards the tracking CCD to stop it from vignetting.  On the USB cameras with the TC237 guider we went to a larger (1.2 inch diameter) window and moved the window back on-axis.