In order to enhance my ability to tweak the focus, I removed the round-head screw holding one of the focus knobs on to the pinion shaft and replaced it with a longer screw. The threads are metric, designated M4-70. On this longer screw I threaded a wing nut and curved washer, followed by a 4 inch long piece of 1/2" wide aluminum bar, 1/16th inch thick. Behind the bar is a split washer and hex nut, followed by another split washer and a large flat washer. The hex nut is used to tighten the connection holding the focus knob to the pinion shaft, and the wing nut can be tightened to engage the bar or loosened to disengage it.

With this modification I am able to adjust the focus in tiny increments while reviewing the results of each change by taking a short exposure of a star. After a few iterations, focus is near perfect, a result that is extremely difficult to achieve with this focuser unmodified.