New main: Focusers
A linear bearing focuser is a type of telescope focuser that uses a linear bearing system to provide a smooth and precise focus adjustment. Unlike rack-and-pinion focusers that use gears to move the eyepiece, linear bearing focusers use a sliding mechanism that is much smoother and less prone to backlash.
Linear bearing focusers are typically of the Crayford design, with a large, flat metal plate that holds the eyepiece and moves back and forth along two parallel rails. The rails are mounted on a sturdy base that is attached to the telescope's optical tube assembly.
The main advantage of a linear bearing focuser is its smooth, precise movement, which allows for very fine focus adjustments. This makes them particularly useful for astrophotography and other applications where precise focus control is essential. Linear bearing focusers are also less prone to wear and tear than other types of focusers, which means they require less maintenance and can last for many years.