Glossary | Telescope accessories | General | Type of build | Zoom eyepiece
A zoom eyepiece replaces several eyepieces with fixed focal lengths. By rotating the eyepiece housing, the lens elements are shifted, so that the magnification varies.
A disadvantage of the zoom eyepiece is the lower apparent field of view. For objects such as the Moon or the planets, it is much more convenient to not to have to change the eyepiece constantly when you want to change the magnification.