I am having a problem with my ST-i guider. It is part of the STF8300 package with the OAG and filter wheel. Basically, the camera does not line up with the light path coming from the prism (see the sample image). In this image the telescope is aimed at a flat panel with a uniform flat image. The light circle appears to be off to the side. If I rotate the camera in its "tube" on the side of the 8300, the light pattern moves accordingly. If guiding selects a guide star in the "dark" area of the image, then guiding fails - I get star faded messages. I have tried "wiggling" the camera in its tube, since there is a slight bit or play there. However, I cannot get the image centered at all. The image shifts only 5-10 pixels. I have tried handling the problem using full calibration of the guider images. My flat looks like the image shown (an average of 25 flats). This has not helped. I need to use darks because there is a hot pixel that the system tends to want to guide on. I tried another camera (QCY III) and had the same issue; the image is off to the side in a similar manner. The issue seems to be that the light coming from the STF8300 prism is not aligned correctly in the tube. The OAG is set up so the ST-i is in the same plane as the 8300. I think I can disassemble the whole unit and orient the OAG at a different 90 degree position. I have not tried this yet, and don't see much of a reason that this would change the alignment. Is there some other adjustment which would allow centering of the guide image?