How Eyepieces Work Why are eyepieces even necessary?
A telescope is an optical system that creates an image, just like a camera lens creates an image on film. In fact, placing a camera at the focus of a telescope will also capture an image, since the telescope becomes the camera lens. But, placing your eye at the focus point of a telescope does not produce an image. Why not? Because your eye is also an optical system. Your eye focuses light just like a telescope does, and it cannot focus on a real image such as that created by a telescope. It requires a virtual image, which is what an eyepiece creates. Take a look at the diagram below. It shows that both a telescope and your eye focus light to a point. Placing an eyepiece at the focal point of a telescope then creates a light beam which is neither converging nor diverging. Your eye can then focus the light beam exiting the eyepiece. Above: How an optical system consisting of a telescope, eyepiece, and eye creates a final image Magnification The most important eyepiece characteristic is f
