Observing basics
天顶
Zenith
The point straight overhead, altitude 90°.
The air mass is thinnest at zenith — the best place for planets.
Related terms
- Pickering scale — A 1–10 scale for how steady a star looks.
- Transit — An inner planet crossing the Sun's disc.
- Occultation — A nearer body hiding a farther one.
- Appulse — The moment two bodies look closest.