In this article
What the tool shows
For the date you choose, the tool lists Mercury, Venus, Mars, Jupiter and Saturn. Each line has three pieces of information. The first is when to look: in the evening after sunset, before dawn, most of the night, or too close to the Sun to see. The second is the zodiac sign the planet sits in. The third is the angle between the planet and the Sun as seen from Earth, which astronomers call elongation. It is measured as a difference in ecliptic longitude, the position along the belt of sky that the Sun, Moon and planets follow.
Everything is worked out in your browser from standard astronomical formulas. No date, no result and no location is sent anywhere.
How the angle becomes a recommendation
The rule is simple. A planet east of the Sun sets after it, so it shows up in the evening sky once the Sun has gone down. A planet west of the Sun rises before it, so it belongs to the morning sky before dawn. When the angle from the Sun is larger than 150 degrees, the planet is nearly opposite the Sun, which means it rises around sunset and stays up most of the night. That situation is called opposition and it is the best time to observe a planet.
If the angle is too small, the planet is hidden in the Sun's glare. The tool uses 18 degrees for Mercury, 10 degrees for Venus and 15 degrees for Mars, Jupiter and Saturn. Venus is so bright that it can be spotted closer to the Sun than the others, which is why its limit is lower.
How to tell a planet from a star
Planets usually shine with a steadier light than stars, which tend to twinkle because their light is a single point disturbed by the air. Planets also keep to the ecliptic, the same line across the sky that the Sun and Moon follow. If a bright, steady point sits along that line, a planet is a good guess.
Brightness helps too. Venus is the brightest, often unmistakable in the evening or morning. Jupiter comes next, a bright white-gold point. Mars varies enormously: it can rival the brightest stars when it is close to Earth and look faint and orange when it is far away. Saturn is steady and yellowish, less bright than Jupiter. Mercury is the hardest, because it stays low in the twilight and is easy to miss.
Why Mercury and Venus never show up at midnight
Mercury and Venus orbit inside Earth's orbit, so from our viewpoint they never wander far from the Sun. Mercury stays within a bit more than twenty degrees of it and Venus within roughly forty-five degrees. That means they can only be seen shortly after sunset or shortly before sunrise, never high in a midnight sky. Mars, Jupiter and Saturn orbit outside Earth, so they can stand opposite the Sun and cross the sky all night.
Conjunctions, binoculars and telescopes
When two planets, or a planet and the Moon, appear close together in the sky, astronomers speak of a conjunction. It is a line-of-sight effect only; the bodies are still millions of kilometres apart. A pair like that is an easy target even from a bright town.
With ordinary binoculars you can often make out Jupiter's four largest moons as tiny points in a row beside the planet. A small telescope is enough to show Saturn's rings. Uranus and Neptune are not in the tool because they are too faint for the naked eye and need binoculars or a telescope and a star chart.
What the tool does not tell you
The tool does not give exact rise and set times, how high a planet climbs, or anything tied to your city. The when-to-look answer is roughly the same all over the world, but your latitude changes how high a planet gets: planets near the ecliptic climb higher for observers close to the equator and sit lower at high latitudes. Use a local sunset time and a free planetarium app for those details.
The sign column and astrology
The sign shown beside each planet is the same zodiac sign that astrologers use in horoscopes. In astronomy it is just a way of naming a 30-degree slice of the ecliptic. If you are curious how a planet in a given sign is described in astrology, remember that astrology has no demonstrated scientific basis; it is a tradition to read for reflection and enjoyment, separate from the observing advice above.
Questions people ask
What does too close to the Sun mean?
It means the planet is within a small angle of the Sun, so it rises and sets almost with it and is lost in the glare. The limits are 18 degrees for Mercury, 10 for Venus and 15 for Mars, Jupiter and Saturn.
Why does the tool say most of the night?
When a planet is more than 150 degrees from the Sun, it is nearly opposite it. It rises around sunset and sets around sunrise, so it is up for much of the night.
Does the result depend on where I live?
Only slightly. The question of evening or morning is roughly the same worldwide, but latitude changes how high the planets climb. The tool does not use your location.
Why are Uranus and Neptune missing?
They are too faint to see without binoculars or a telescope, so a simple naked-eye guide leaves them out.
Is my date sent anywhere?
No. The calculation runs in your browser, and nothing is stored or transmitted.