# Focal reducer

Also called: reducer, f/6.3 reducer.

A lens that shortens a telescope's focal length — an f/6.3 reducer turns an f/10 SCT into a wider-field instrument.

Reducers are the opposite of Barlows: they lower the magnification of every eyepiece and widen the field. They're mainly used on long-focus SCTs, whose narrow fields can't otherwise frame big objects.

**Related:** [Schmidt–Cassegrain](https://astropilot.space/glossary/schmidt-cassegrain.md), [Barlow lens](https://astropilot.space/glossary/barlow.md), [True field of view](https://astropilot.space/glossary/true-field.md)

From the AstroPilot astronomy glossary: https://astropilot.space/glossary/focal-reducer