Elongation is the number of degrees a planet stands from the Sun in ecliptic longitude. East of the Sun it is positive: the planet shows in the evening sky, after sunset. West of the Sun it is negative: the planet shows in the morning sky, before sunrise.
01What the number says
- ·18° and under: the planet is lost in the Sun's glare. It rises and sets with the Sun and cannot be picked out with the naked eye.
- ·Between 18° and 150°: the planet has pulled away from the Sun. East of it, it shows in the evening; west of it, in the morning, for a limited time.
- ·150° and over: the planet is almost directly opposite the Sun. It rises as the Sun sets and stays above the horizon all night.
These two thresholds (18° and 150°) are this product's own choice: they are set as a visibility rule, not a traditional interpretive threshold.
02How far each planet can go
Mercury can stand at most about 28° from the Sun and Venus about 47°, because both orbits lie inside the Earth's. That is why they show only near the Sun, in the evening or the morning. Planets from Mars outward can reach any distance; the period when one stands opposite the Sun falls in the middle of its retrograde stretch.
03What it is not
Elongation is not brightness and not height above the horizon. Whether a planet can actually be picked out depends on light, atmosphere and place, and the product does not model them. Uranus, Neptune and Pluto need a telescope even when their elongation is favourable.
In traditional astrology planets very close to the Sun have a name of their own; the 18° threshold in this piece should not be confused with that tradition.
04Where you see it on the page
On the Sky page, the "Tonight" card writes each planet's distance from the Sun in degrees; open "Show the calculation" to see it. For the tolerance of angles, see the orb piece.
Updated 2026-10-02.
The arithmetic is free and stays free. An account is what lets you save a chart, compare it with a second one, and read an interpretation of it.