What the terms mean
- Opposition
- Earth passes between the Sun and an outer planet. The planet rises as the Sun sets, stays up all night and is at its closest and brightest. The best time to look at Mars, Jupiter or Saturn.
- Greatest elongation
- Mercury and Venus orbit inside Earth, so they never stray far from the Sun. Greatest elongation is the moment they appear furthest from it, and the easiest time to catch them in twilight.
- Conjunction
- Two planets appear close together in our sky. They are not actually near each other, they simply line up along the same direction from Earth.
- Meteor shower
- Earth ploughs through the dust trail left by a comet or asteroid. The grains burn up high in the atmosphere. Peak dates shift by a day either way from year to year.
Eclipses are not listed here because they need more precise calculation than this page performs. Once you know what is coming, check Sky Tonight for where to look from your own back garden.