What are the optimum back focus distances for Celestron SCTs?

The back focus distances are as follows:

SCT Back focus distance from primary mirror baffle tube lock ring (in)
C5 5 in
C6 5 in
C8 5 in
C925 5.475 in
C11 5.475 in from 3 in-2 in Reducer Plate 
5.975 in from 3 in Primary Mirror Baffle Tube Lock Ring
C14 5.475 in from 3 in-2 in Reducer Plate 
5.975 in from 3 in Primary Mirror Baffle Tube Lock Ring


Please see the EdgeHD FAQs for corresponding numbers for that optical design.

Updated 12/27/13