Background: My understanding is the STF-8300 CCD with FW8 and the OAG-8300 with STi camera combo is 57.5mm of backfocus. My telescope is the Celestron EdgeHD 1400, which requires 146mm of backfocus and the Celestron T-Adapter gives 88.5 of backfocus, which leaves the standard T2 length of 55mm for camera/etc. This means (i think) the STF/FW8/OAG combo is 2.5mm longer than the standard T2 length of 55mm, and I'm struggling with finding the right permutation of spacers (instead of the T-Adapter) to give me 57.5mm for this STF/FW8/OAG setup. Question: is the STF/FW8/OAG combo really 57.5mm of backfocus, or is it 55mm by chance, or something else? Extra credit question: Does anyone happen to know what adapters/spacers to use for the STF/FW8/OAG to achieve the 146mm required for the Celestron EdgeHD 1400?