[JA]

Hello H,

It would surprise me if the manufacturer hadn't provided for the use of filters with their design and that sounds like what the M42 to M48 adaptor, that Merlin mentioned, might be about. Of course as per your drawing the camera has a M54 x 0.75 female thread so perhaps another adaptor is also required or an alternate mounting plate is available for larger format cameras. Perhaps question the manufacturer or your vendor directly for a solution.

Be that as it may, if you run in to difficulty with adpators/back-focus distance, etc.. AND if you are adventurous and you can only use the mounting plate you showed in the drawing, you could .....

fix an M48 female threaded ring (perhaps use a photographic filter 48mm stepdown ring) to the inside flat surface of the front conical mounting plate, which could serve as a mounting thread for m48 filters (albeit difficult to changeout). Of course this is all provided that it doesn't foul (contact) anything in the area on the telescope corrector. As a 48mm filter, with perhaps 44mm in open aperture, it shouldn't reduce or obscure the camera beyond what the telescope's own 37mm internal bore on the mounting plate already does. Diagram attached of above concept.

Best
JA