Spherical aberration - Definition and Overview

Spherical aberration is an inherent property of telescopes using spherical mirrors with focal ratios shorter than f/10. Light from a distant point source (such as a star) is not all focused at the same point. Particularly, light striking the inner part of the mirror focuses further from the mirror than light striking the outer part of the mirror. As a result the image cannot be focused as sharply as if the aberration were not present. Because of spherical aberration telescopes shorter than f/10 are usually made with non-spherical mirrors or with correcting lenses.

   Spherical aberration may be present in other types of optical systems, such as those with lenses, as well.

See also

• Aberration in optical systems
• Schmidt corrector plate
• Parabolic reflector
• Ritchey-Chrétien telescope