Planet events and alignments

Pick a place at the top (a City, typed Lat / lon with its time zone, or Here) — it’s shared with eclipses and meteor showers in this browser. Choose where to start and how far ahead to look (12 months up to 20 years); twenty years takes several seconds to search.

How to use it

Events is a timeline, month by month. Each line has the date and exact time in your time zone, what happens, and — on the right — when you can see it from your place ("evening, 14° up") or why not. Tick the kinds of event you want:

Planet pairs — the closest approach of two planets (the moment their separation is least, which is what you see; it is within hours of the formal conjunction in longitude or right ascension). Pairs within sets the widest separation to list, from half a degree to 5°.
Moon and planets/stars — the Moon passing a planet (within the same limit) or one of the bright stars and clusters near the ecliptic: Aldebaran, the Pleiades, Elnath, Pollux, the Beehive, Regulus, Spica, Zubenelgenubi and Antares (within 2°).
Planets and stars — a planet passing one of those stars, within 3°.
Occultations — the Moon covering a planet, a star, or crossing the Pleiades or the Beehive somewhere on Earth. Open one to see whether it happens from your place, with the times it disappears and reappears and how high the Moon is.
Parades — nights when at least 3, 4, 5 or 6 planets are above the horizon together in a dark enough sky. See below.
Oppositions of Mars to Neptune, greatest elongations of Mercury and Venus, stations (where a planet turns retrograde or direct), Mars’s perihelion, aphelion and closest approach, and conjunctions with the Sun (hidden by default — you can’t see them).

Only what I can see from here keeps an event if, within a few hours of it (a day for slow planets), every object in it is at least 5° up while the Sun is at least 6° below the horizon (10° up for single-planet events). Tap an event for:

the best moment to look, the twilight then, and each object’s altitude, bearing and magnitude;
a picture of that part of the sky with the horizon, compass bearings and the Moon’s phase (the whole horizon for a parade);
for close pairs, a binocular-sized field of view with north up and east left;
Add to calendar, an .ics file for this one event. Export .ics at the top saves every event in the list as filtered.

Ecliptic chart plots each planet’s position along the ecliptic against the date, for up to three years: the planets drift east (to the left) and every so often turn back — the thick stretches are retrograde. The yellow band is the Sun; a planet crossing the dashed line is at opposition. Below it, Retrograde loop draws a planet’s next loop as it really looks against the stars (longitude across, latitude up, stretched so you can see it).

Tonight is a table for today at your place: each planet’s rise, highest point (with its altitude), set, magnitude, lit fraction, apparent size, distance from the Sun and when in the night it’s up — plus the Moon.

What counts as a parade

The news calls it a "planet alignment" whenever several planets are in the evening or morning sky at once. They never line up closely: all planets lie near the ecliptic, so at best they make an arc across the sky, usually more than 90° long. Here a parade is the run of nights on which, at some moment with the Sun at least 6° below the horizon, at least N planets are at least 5° above your horizon together. The list shows each run once, at its best moment (the most planets, then the smallest spread), with the span: the largest angle between any two of them. By default only the five naked-eye planets count; Include Uranus and Neptune adds the two that need binoculars or a telescope. Mercury and planets near the horizon need a clear, flat view, and in bright twilight you may not see all of them at once.

For eclipses and meteor showers see eclipses; for the Sun and the Moon on one day, sun and moon; for what a telescope or binoculars will show, optics; for photographing a conjunction, night-sky photography.

How it is calculated

Positions come from the site’s shared astronomy core: VSOP87 for the planets, Meeus’s lunar theory for the Moon, with light time, aberration, nutation and precession; star positions are J2000 (Hipparcos) precessed to the date. Events are found by sampling (every 4 hours for the Moon, half a day or a day for the planets) and refining each minimum, maximum or crossing to about a minute. The Moon’s position from your place includes its parallax, which can shift it by a degree — why an occultation seen in one country is a near miss in the next.

Checked against published dates: the Jupiter–Saturn conjunction of 21 December 2020 (18:21 UT, 6′ apart), Mars’s opposition of 13 October 2020 and its closest approach on 6 October (62.1 million km), its stations on 9 September and 14 November 2020, Venus’s greatest eastern elongation of 24 March 2020 (46.1°), Venus in the Pleiades on 3–4 April 2020, and the occultation of Mars by the Moon on 8 December 2022 (seen from Los Angeles from 02:30 to 03:29 UT, and from London from 05:01 to 05:59 UT).

Limits

Times are good to a minute or two; separations to an arcminute or so. For occultations near the edge of the Moon’s track (a graze) the tool can’t tell reliably whether you’ll see one.
"Visible" assumes a flat horizon and a clear sky; it doesn’t know about hills, trees or haze. Objects within 10–15° of the Sun are flagged as lost in its glare.
Stars are a short list of the brightest near the ecliptic; fainter stars and asteroids aren’t searched.

Privacy

Everything is calculated in your browser; nothing is sent anywhere. The place you choose (and your own location, if you use Here) stays in this browser’s local storage. Calendar files are made in the page and saved by your browser.