Dual Speed Focuser Knob Conversion

thingiverse

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 stabilize the focuser housing by bracing your thumb and/or pointer finger against it for added stability. Alternatively, you can use both hands to gain even more control. For standard focus, simply rotate the middle knob. Fits dual-speed knobs made in the style of GSO, featuring a 37mm OD fine-focus dial and a hole precisely designed for a 4mm OD focuser shaft. This product also fits SkyWatcher-style 3.75mm OD shafts and possibly other types as well. The accompanying photos show an Orion and a Crayford focuser from an unbranded manufacturer. If installed on a smaller diameter shaft without using a coupler or adapter sleeve, the assembly will not turn concentrically with the shaft, which means you cannot use a fixed housing or bracket attached to the focuser body. Press the two 3D-printed knobs onto the dual-speed assembly, paying close attention to 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. Do not force the pieces together with a press or by putting all your weight onto it. Remove the original knob from the focuser and attach the dual-speed assembly to the focuser shaft via two set screws.