Here are some common terms associated with telescopes:
- concave - lens or mirror that causes light to spread out.
- convex - lens or mirror that causes light to come together to a focal point.
- field of view - area of the sky that can be seen through the telescope with a given eyepiece.
- focal length - distance required by a lens or mirror to bring the light to a focus.
- focal point or focus - point at which light from a lens or mirror comes together.
- magnification (power) - telescope's focal length divided by the eyepiece's focal length.
- resolution - how close two objects can be and yet still be detected as separate objects, usually measured in arc-seconds (this is important for revealing fine details of an object, and is related to the telescope's aperture).