# Refractor

Also called: achromat, apochromat, apo, ED.

A telescope that uses lenses: sharp, contrasty, low-maintenance — with no central obstruction.

Refractors are the classic spyglass shape. Simple two-lens achromats show some [false colour](https://astropilot.space/glossary/chromatic-aberration) around bright objects; apochromats (“apos”, often with ED glass) correct it. Small apos are superb for wide fields, the Moon and travel; large refractors become very expensive per inch of aperture.

**Related:** [Reflector](https://astropilot.space/glossary/reflector.md), [Chromatic aberration](https://astropilot.space/glossary/chromatic-aberration.md), [Orientation](https://astropilot.space/glossary/orientation.md), [Dew](https://astropilot.space/glossary/dew.md)

From the AstroPilot astronomy glossary: https://astropilot.space/glossary/refractor