This paragraph explains the DSLR adaption to a Skywatcher Esprit 100 including a filter drawer.
The scope comes with a M48 adapter for the flattener which is optimal for DSLR adaption using their T-rings. I intend to use the DSLR with a CLS-Filter during most of my photo sessions. Clamping a XL clip-filter directly into the DSLR body is possible, but produces unwanted vignetting. Hence I realized a way to use unmounted 50 mm filters. For that I machined an adapter for the TS-Filterschublade. This filter drawer is a compromise in order to realize a short optical path length. From the mechanical point of view it is improvable. As long one works very carefully and tries to avoid touching it, it’s passable solid.
The picture shows the adapter M66x1 to M48x0.75 and the M48 filter drawer with EOS bayonet at its backside. To meet the requirement of the flattener the optical length of DSLR + Filter drawer + adapter is 63 mm. The adapter has been manufactured out of two parts: an outer part made of high-strength aluminium and an inner part made out of brass. This process was necessary in order to get a M48 thread length of only 2 mm. Due to the small optical length of the drawer the M48 thread is only 2 mm deep. If a bolt is screwed in deeper than 2 mm it collides with the filter insert.
The focuser offers a M74x1 thread this is adapted for the orignal flattener with its M66x1 by an adapter which is in the scope of supply. Everything fits well, but you now already have two adapters between focuser and flattener! This means you have many positions, where you can come into trouble because of loose connections. So one has to check many connections before taking the first frame. My system run reliable nevertheless.
The final DSLR adaption with all adapters is shown in next picture. This set-up has a focal plane distance of 63 mm to the end of the aluminium ring ready for a direct connection to the original Skywatcher flattener. The last picture gives an impression of the whole chain mounted at the telescope before a nightly session. Here is a drawing of the adapter.