# Chromatic aberration

Also called: false colour, false color.

A purple or yellow fringe around bright objects in simple lens telescopes, because lenses bend colours differently.

A lens focuses blue and red light at slightly different points, so an achromatic [refractor](https://astropilot.space/glossary/refractor) shows a violet halo around bright stars, the Moon's edge and planets. Apochromats with special glass all but remove it; mirrors never show it.

**Related:** [Refractor](https://astropilot.space/glossary/refractor.md), [Reflector](https://astropilot.space/glossary/reflector.md)

From the AstroPilot astronomy glossary: https://astropilot.space/glossary/chromatic-aberration