# Limiting magnitude

Also called: NELM, naked-eye limiting magnitude.

The faintest magnitude you can see — with the naked eye (NELM) or through a given telescope.

Your naked-eye limiting magnitude measures the sky: about 4 or less in a city, 5–6 in the suburbs, 7 or more at a truly dark site. A telescope's limit adds roughly 5 × log₁₀(aperture ÷ 7 mm) magnitudes to that — so the darker your sky, the deeper every telescope goes.

**At the eyepiece:** Estimate your NELM by counting stars inside a known triangle of stars, or simply note the faintest star you can hold in the Little Dipper.

**In AstroPilot:** Gear pages give each telescope's limiting magnitude under a dark sky.

**Related:** [Magnitude](https://astropilot.space/glossary/magnitude.md), [Bortle scale](https://astropilot.space/glossary/bortle-scale.md), [SQM](https://astropilot.space/glossary/sqm.md), [Light grasp](https://astropilot.space/glossary/light-grasp.md)

From the AstroPilot astronomy glossary: https://astropilot.space/glossary/limiting-magnitude