Occultation

One object passing in front of another and hiding it completely, most often the Moon in front of a star or planet. A star vanishes instantly at the Moon’s edge, since the Moon has no atmosphere. Timing these moments precisely is a useful amateur contribution.

ToolsThe Moon tonight

Related terms

Transit: A small object passing in front of a larger one without hiding it: Mercury across the Sun (next on 13 November 2032), one of Jupiter’s moons across the planet, or the ISS across the Sun or the Moon. For the Sun, a solar filter is essential.
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.
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.

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