Observing basics
地平高度
Altitude
Angle above the horizon: 0° at the horizon, 90° at zenith.
Below 10° atmospheric extinction is heavy; most observers skip it.
Related terms
- Averted vision — Looking slightly off-target to use rod-rich retina.
- Red light — Reading charts under red light to keep dark adaptation.
- Pickering scale — A 1–10 scale for how steady a star looks.
- Transit — An inner planet crossing the Sun's disc.