# Seeing

Also called: atmospheric seeing, twinkling, steadiness.

How steady the air is. Good seeing gives sharp, still views at high power; bad seeing makes stars boil and twinkle.

Pockets of warmer and cooler air bend starlight slightly differently, so stars twinkle and planets shimmer. In good seeing a star at high power is a tight point with a steady ring around it; in poor seeing it's a boiling blob. Seeing matters most for planets, the Moon and close double stars — and much less for faint, low-power deep-sky views.

It's caused by turbulence at all heights: the jet stream high up, wind over hills, and heat rising from roofs, roads and the telescope itself. Seeing and [transparency](https://astropilot.space/glossary/transparency) are different things — crystal-clear nights are often turbulent.

**At the eyepiece:** Watch a bright star at high power: if it's steady, go for planets and close doubles; if it boils, switch to low-power deep-sky targets.

**In AstroPilot:** Hour by hour on Tonight rates seeing from 1 (poor) to 5 (excellent), estimated from jet-stream winds and wind shear.

**Related:** [Transparency](https://astropilot.space/glossary/transparency.md), [Jet stream](https://astropilot.space/glossary/jet-stream.md), [Maximum useful magnification](https://astropilot.space/glossary/max-magnification.md), [Cooldown](https://astropilot.space/glossary/cooldown.md)

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