# Eye relief

How far your eye must be from an eyepiece to see the whole field; 15–20 mm is comfortable, and needed with glasses.

Short-focus Plössls have very short eye relief, so you press your eye close. Modern designs keep 15–20 mm at any focal length — important if you observe with glasses (needed for astigmatism; short- or long-sightedness can simply be focused out).

**Related:** [Eyepiece](https://astropilot.space/glossary/eyepiece.md), [Barlow lens](https://astropilot.space/glossary/barlow.md)

From the AstroPilot astronomy glossary: https://astropilot.space/glossary/eye-relief