This is a collection of focusing aid for different diameters of lenses / focusser rings.
In astrophotography or macro photography it is essential to focus as precise as possible. By turning the focus ring on DSLR lenses by hand, it is quite difficult to lock down on the best focus possible (most likely you will be able to turn the focus ring by a degree precision). With this tool attached, it is possible to get really precise focus, as you will be turning a screw on one of the two parts. Which is increasing the precision 50-fold to 100-fold (depending on your skills).
The rings are designed for given diameters. The rings may flex for 2-3mm in diameter. I would recommend, lining the rings inner surface with velours tape. One ring has to be attached to the focus ring, the second ring has to be attached to the lens barrel (non-moving part)
What you will need:
1x ring with pin
1x ring with fork
2x conical knurled knob (from https://www.thingiverse.com/thing:2418824 )
2x flat knurled knob (from https://www.thingiverse.com/thing:2418824 )
2x M4x45mm or M4x50mm hex head for conical knurled knob
2x M4x40 hex head for flat knurled knob
4x M4 nut
M4 tap to cut threads
(hot) glue to attach screws in knobs
Current set of ring diameters is:
72mm (f), 74mm (f, p), 78mm (f, p), 80mm (p), 84mm (f, p)
f ... ring with fork
p ... ring with pin
If time permits, I may add further diameters on request!