Observing basics

暗适应
Dark adaptation

Eyes adjusting to darkness over 20–40 minutes.

One glance at a phone screen undoes most of it.

Related terms

Altitude — Angle above the horizon: 0° at the horizon, 90° at zenith.
Azimuth — Horizontal angle measured clockwise from north.
Zenith — The point straight overhead, altitude 90°.
Meridian — The great circle from north through zenith to south.