I ordered some replacement knurled knobs from McMaster-Carr. They are 16mm
diameter heads (vs 10mm), and have 20mm long M4 x .70 thread shafts (vs ~13mm
long). They stick out like a bunch of sore thumbs. With these I won't have
to guess about whether I'm adjusting the zoom knob on the ocular, or accidentialy
releasing the ocular to its doom.
Much better. Two of the original knobs are in the middle on the focuser mounting bracket and the diagonal's 2" to 1-1/4" reducer. Those shouldn't need any adjusting after they are tightened for the evening, so I'll leave those knobs where they are. The new ones were black, so I painted the heads white with some fingernail polish.