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SCENARIO II ：SMALL SIZED CAMERA LENS/TELESCOPE WITH FLATTENER
As aforementioned, the back focus of DSLR lens is fixed. Therefore, the optimal back focus distance (OBFD) in such
setup must be met strictly. This is applicable to telescope flattener, which can be considered as a lens. The only
difference is the mounting method, bayonet mount for camera lens and regular threaded mount for flattener.
To reach the OBFD in such system, the fine adjustment adapters can be used: the 20090 (small size)/020089 (medium
sized) are comprised of 5 different pieces of adapter of 0.5/1/2/3/7mm respectively. They can be combined into
various thickness to meet specific demands. Tailored screw may require for the adapter(s).
While using the fine adjustment adapters in small sized camera, the external adapter (020085) needs to be replaced
by threaded external adapters (020056 and 020083). The 020083 is included in the standard package of small off
axis guider (OAGS)
Model
Back focus consumed
Where to acquire
Whether tailored
screws are needed
020056
3mm
Purchased separately
Likely
020083
3mm
Purchased separately
020090
External adapter 4mm；
Fine adjustment
adapters13.5mm
（0.5+1+2+3+7）
Purchased separately
020072/
020074
10mm
Purchased separately
（72 for CANON EF
MOUNT，74 FOR
NIKON F MOUNT）
