Observing basics
星等
Magnitude
A logarithmic brightness scale: smaller numbers are brighter.
Five magnitudes is a factor of 100; Sirius sits at −1.46.
Related terms
- Zodiacal light — Sunlight scattered by interplanetary dust, a faint cone.
- Air mass — Relative air path; 1 at zenith.
- Extinction — Atmosphere dimming starlight.
- Dark adaptation — Eyes adjusting to darkness over 20–40 minutes.