brenski Looking to see if it's possible to connect a Zwo ASI585mc to a Takumar 200mm F/4 (M42 thread)
First, keep in mind that the Takumar uses a 42mm thread with 1mm pitch (the original Pentax lens' specs), while the ASI585 uses a 42mm with 0.75mm pitch. So you will need a M42P1 to M42P0.75 adapter for them to seat properly. They are quite common; even Baader has an adpater. They are also called M42x1.
Next, the Pentax lenses have a back focal length of 45.5 mm from its flange. The ASI585's flange (the "telescope end" of that black ring) to sensor distance is 17.5mm.
So you will need a total spacing of 45.5-17.5 = 28mm, with the proper gender.
Keep in mind that unlike real cameras, ZWO camera's flange to sensor distances are only spec'ed to be accurate to +/- 0.5mm, so you may need to experiment a bit. But you can start with a 28mm spacer to see if you can achieve infinite focus at the right spot on the lens. Use a shorter spacer if you can't achieve infinite focus.
The Baader adapter has 7.5mm optical path, so you would need an extra 20.5mm spacer. You can try 20mm -- that should let you use the lens' manual focuser to get to infinity focus.
Chen