The amazingly versatile Celestron 8 mm - 24 mm zoom eyepiece allows you to choose from a variety of magnifications in a flash Simply grip the rubberized barrel and turn it slowly while looking through the eyepiece, and then pick the best power for the object you are observing. Alternatively, you can use the lowest magnification (24 mm) to find an object and center It in your field of view, and then increase the power until the desired view is achieved. It is fast and easy, and lets you examine any object at various magnifications without requiring you to physically change eyepieces.