Dual Speed Focuser Knob Conversion

Convert a single-speed to a dual-speed focuser without having to drill and/or install a bracket. To use fine focus, grasp the inboard knob with your pointer finger and thumb while rotating the outboard fine focus dial with your middle finger. You can also brace your thumb and/or pointer finger against the focuser housing for additional stability. Alternatively, use two hands. For standard focus, rotate the middle knob.

Fits GSO-style dual speed knobs with a 37mm OD fine-focus dial and a hole for a 4mm OD focuser shaft. Also fits SkyWatcher-style 3.75mm OD shafts and possibly others. The photos show an Orion and an unbranded Crayford focuser. If installed on a smaller diameter shaft without the use of a coupler or adapter sleeve, the assembly will not turn concentrically with the shaft which precludes the use of a fixed housing or bracket attached to the focuser body.

Press the two 3D-printed knobs onto the dual-speed assembly noting the alignment of the flats on the base. You might need to clean up and sand/file the inner diameter of the 3D-printed knobs for a snug fit. Don't force the pieces together with a press or by putting all your weight onto it. Remove the original knob on the focuser and attach the dual-speed assembly to the focuser shaft via two set screws.