I'm not sure how to adjust the prism on the M68 OAG. The owners manual is for the smaller OAG and doesn't provide any direction for this newer, larger OAG. I see there is a gold set screw on the side of the housing where the guide camera sits, but not sure what it is for. There are also two small, silver phillips head screws that look like they hold the prism, but they don't look like adjustment screws. Thanks.