This adapter allows you to connect the Prima Luce Lab ARCO 2" robotic rotator to the ESATTO 4" microfocuser and control it via the dedicated port on the ESATTO.
It has an optical thickness of 1mm, so adding this adapter will increase the thickness of the ARCO 2" from 20mm to 21mm.
ARCO 2" rotator connected to ESATTO 4" microfocuser by adding the optional PL3600423: free aperture after ARCO 2" is 51mm.