How the lunar node is calculated
The calculator runs the same calculation as the UmbraLux app, in three steps:
- 1
Turn the clock time into Universal Time
Your birth time is the clock time at your birthplace. With the time zone that applied there on that day (the IANA time zone database knows summer times and older rules), it becomes Universal Time (UTC). Without a time, the calculator takes your whole birthday at your birthplace.
- 2
Calculate the true node
From the Moon's position and velocity at that moment the calculator finds the plane of its orbit and where it crosses the ecliptic: the true (osculating) lunar node.
- 3
Read the sign
The longitude divided by 30° gives the sign: 0° to 30° is Aries, 30° to 60° Taurus and so on (tropical zodiac). The remainder is the degree within the sign.
Example: 15 May 1990, 14:30, Berlin
On 15 May 1990 summer time applied in Berlin (UTC+2), so 14:30 was 12:30 Universal Time. At that moment the North Node stood at 10°15′ Aquarius.
The North Node had entered Aquarius on 22 May 1989 and left it on 18 November 1990: anyone born in that time has the North Node in Aquarius.
What the lunar nodes mean in astrology
Astrology reads the North Node as the direction you want to grow in, and the South Node as the familiar you bring with you.
In the library
Questions about the lunar nodes
True or mean node?
The calculator uses the true node, as the UmbraLux app does. The mean node smooths out the wobbles of the Moon's orbit and lay up to almost 2 degrees off from 1940 to 2024; on 3 percent of the days that put it in another sign.
How long does the node stay in a sign?
About a year and a half: the node moves backwards through the whole zodiac in 18.6 years.
Where is my South Node?
Exactly opposite the North Node, in the opposite sign and, with your birth time, in the opposite house.
How accurate is the calculator?
In 5,000 samples from 1940 to 2024 the true node lay within one arcminute of a calculation on the Swiss Ephemeris.
Is my data stored?
No. The calculation runs in your browser; your date, time and place are neither sent nor stored. Only your device remembers your last entry, and you can delete it below the form.
Sources
- Jean Meeus: Astronomical Algorithms, 2nd edition, Willmann-Bell 1998: Planetary positions, ecliptic coordinates
- Astronomy Engine (Don Cross) : The ephemeris the calculator uses
- IANA Time Zone Database : Time zones and summer times of the birthplace
- GeoNames : Coordinates and time zones of the places (CC BY 4.0)
- Wikipedia: Lunar node
More calculators
- AscendantThe sign rising in the east when you were born, to the arcminute.
- Sun signThe sign of the Sun at your birth, on the day it changes sign too.
- Moon signThe sign the Moon stood in when you were born.
- Birth moon phaseNew moon, full moon or in between: the phase, the light and the age of the Moon at your birth.