Left pointing hand navigation decoration Return to “Telescopes from the Ground Up” Left pointing hand navigation decoration
Telescopes from the Ground Up

Focal point

The focal point of a lens or mirror is the point in space where parallel light rays meet after passing through the lens or bouncing off the mirror. A "perfect" lens or mirror would send all light rays through one focal point, which would result in the clearest image.

Diagram of how a perfect lens creates a focal point.
Return to “Telescopes from the Ground Up”