I just got myself a ZS73 with a Flat 73 adjustable. At the moment I'm waiting for my camera to come back from being astro modified but I have a question regarding the back focus to the flat 73.
When reading the WO Flat61/73 back focus diagram I see that I need 67.7mm between the edge of the flattener to the image plane.
Now this is the adapter I have to reach this back focus:
Canon EOSM100 flange distance= 18 mm, EOSM to T2 adapter (27.5mm) + Zwo M42 to M48 spacer (16.5mm)
That gets me to 62mm.
Now I also have an Optolong 2" L Pro filter in the image train connected to the flat 73. With the filter installed the flattener adjuster sits at about 5mm out due to the thickness of the filter by default.
So I end up at 67mm as a starting point...
My question are
1) Am I calculating this correctly?
2) Will I be able to get the correct back focus for a flatfield image?