[bojan]

Now about stops or "clicks"....
I decided to start with hex spacer with M3 thread.
I have steel balls ø3.2mm, so all I need to do is to widen the hole to ~ø3.3mm ~6mm deep, then cut M6 thread ~3mm long and cut the spacer to 10~12mm.
The assembly as pictured below (without ball and spring) will be screwed into platic holder at apprppriate position, then it will be used as guide to mark the position of the rotary part with drill so the ball can click into the recession and the eyepiece tubes are properly aligned.