With my BRC-250 I used an adapter that Texas Nautical Repair had made for me to reach the correct back focus with my FLI DF-2 focuser and SBIG ST-8XE & color filter wheel. The correct back focus is critical when focusing with either the FRC-300 or the BRC-250.

If you are using a FLI focuser (DF-2 or PDF) You should place the custom made adapter between the scope and the focuser then attach your camera or CCD imager to the focuser. Then send the focuser the center starting position "0". Once at the "0" position use the scopes helical focuser to find a real close focus while you are taking short exposures (CCD). Once you find a close focus point with the helical focuser on the scope "LOCK IT DOWN" now you can just fine tune the focus with the FLI focuser. You will "not" need to touch the helical focuser any more in the future, (unless you change to a new camera or focus set up) it's all done with the FLI focuser from here on out..

The correct distances can be seen in the above diagram.

The FRC-300 and BRC-250 have the same exact back focus.

Stephen T. Roffo Jr