Hi, I should calculate exactly the thickness of a T2 adapter. In the table I see that back focus of the STF-8300 + FW8 is 35,4mm. I do not understand the reference to 2mm and 3mm filters. What kind of filters are? I only have a set of 36mm Baader LRGB in the filter wheel ... Regards Giulio
Due to the refractive index of the glass, adding a filter has the effect of increasing back focus slightly. 2 mm thick filters increase the back focus by about 0.66 mm or 0.026". 3 mm thick filters increase the back focus by about 1 mm or 0.039".
Thank you Doug, this is very important for me. So as the Baader LRGB 36mm set is 2mm thick, my back focus is 34,7 and not 35,4
Giulio, The thicker filter actually creates more backfocus. The STF-8300 and FW8-8300 is 34.7mm with the 2mm filters. Che chart is below. Are you using the threaded adapter plate on the front of the wheel? That adds 3.7mm Adapter Plate, T-thread
Thank you Tim for your clarification! Yes I am using the threaded adapter plate and I didn't consider it. Giulio
