Tables giving the positions of celestial objects and the times of coming events: rising and setting, Moon phases, conjunctions, satellite passes. Once printed in books, they are now computed in an instant. They are the basis for planning a night out.
ToolsWhat to see tonight?, The Moon tonight, ISS passes
Related terms
- Moon phases
The Moon’s changing look depending on how much of its sunlit side we see: new Moon, crescent, first quarter, gibbous, full Moon, then back again. The full cycle, the lunation, lasts 29.5 days. For relief, prefer the quarters to the full Moon, which looks flat.
- Conjunction
The apparent meeting of two objects in the sky, such as the Moon and Venus, while they stay far apart in space. A planet is also said to be in conjunction with the Sun when it is lost in its glare and invisible. Close planetary conjunctions are lovely naked-eye sights.
- ISS (International Space Station)
The largest crewed satellite, orbiting about 400 km up and circling the Earth in about 90 minutes. It looks like a very bright, steady point crossing the sky in a few minutes. It is only visible around dawn or dusk, when it is sunlit while the observer is in darkness.
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