The 7885 part is designed to cover the APS-C sensor size. I’ve not tried it with my Borg 71FL, but the Borg Japan size, shows that it is compatible with both the 50FL and 71FL ( http://www.tomytec.co.jp/borg/products/partsDetail/summary/107 ) . This part was available before either of these scopes, so perhaps it is not quite optimal at the longer 400mm focal length?
DigiBorg 
Hey Ted,
As I read the table, only 2 of the 29 versions listed have an asterisk denoting they are suitable for APS-C sensors.
Is just two correct?
Or perhaps what is meant is that only those two listed for the 60 and 45 setups are OK to use for APS-C for those objective sizes.
It’s a mite confusing…
Thanks!
Perry
The 7885 part is designed to cover the APS-C sensor size. I’ve not tried it with my Borg 71FL, but the Borg Japan size, shows that it is compatible with both the 50FL and 71FL ( http://www.tomytec.co.jp/borg/products/partsDetail/summary/107 ) . This part was available before either of these scopes, so perhaps it is not quite optimal at the longer 400mm focal length?
Stuart
At astronomy stand point, 7885 is not optimized for 400mm focal length. It works for nature photography well though.
Ted