Around 30–50 N·cm holding torque is typically sufficient for most focusers, and a standard NEMA 17 with microstepping (e.g., 1/16 or higher) usually provides enough resolution without needing a gearbox, though 0.9° motors offer slightly finer native precision than 1.8°. To reduce vibration and resonance, use lower current, acceleration ramps, and a flexible coupler, and for long sessions set the current just high enough to avoid missed steps while lowering holding current to manage heat.