Observing basics
冲
Opposition
A superior planet opposite the Sun, visible all night.
At a Mars opposition the distance can close to 55 million km.
Related terms
- Seeing — How much the atmosphere smears a star's image.
- Transparency — How well the sky passes starlight, set by water vapour and dust.
- Light pollution — Artificial light brightening the night sky and hiding faint objects.
- Bortle scale — A 1–9 scale describing how dark a night sky is.