The Astrolium south node calculator returns the descending node by sign and house, paired with the north node on a single output, in under 30 seconds. Math runs on the Swiss Ephemeris in your browser. No login, no email, no upload.
The south node sits inside the natal chart feature, where the full nodal axis reads against every other point. For the trajectory-side sister point, see the north node calculator. For the third fated point modern astrologers pair with the nodes, see the vertex calculator. For the commitment asteroid often layered against the nodes, see the juno calculator.
What you get
The south node is the descending intersection of the Moon's orbit with the ecliptic. It sits exactly 180 degrees from the north node — same line, opposite end. The full nodal axis is one structure read from two angles.
The axis completes a backward circuit of the zodiac in 18.6 years, which is why people born within a window of months share a node sign. The house assignment — what area of life carries the familiar pattern — depends on birth time and rising sign. That's the part that makes the south node personal. For background on choosing the right house system for this reading, see the house systems guide.
What the south node means in astrology
By sign, the south node names what the chart already knows. South node in Cancer carries inherited care, emotional fluency, family memory. South node in Capricorn carries inherited discipline, structure, the executive habit. The sign describes the qualities already accessible without effort.
By house, the south node names the arena where that mastery sits. South node in the 7th carries partnership patterns ready to repeat. South node in the 10th carries default authority — sometimes welcome, sometimes a trap.
The standard integration question: where does the south node become a comfort zone instead of a foundation? When transits hit it — eclipses, hard squares from the outer planets — the chart often asks whether the easy thing is still serving.
Mean Node vs True Node
Same geometry as the north node, mirrored.
Mean Node averages the long-term motion of the nodal axis. Smooth retrograde, 18.6-year cycle, predictable to the day. Standard in most traditional and modern Western charts.
True Node computes the instantaneous orbital intersection. It oscillates and briefly goes direct from time to time. Up to 1.7 degrees of difference from Mean Node — usually under one degree, but enough to flip the sign if the node sits on a cusp.
Astrolium computes both and shows the delta. Pick the convention your school uses, or compare the two side by side.
How Astrolium calculates the south node
The math runs on the Swiss Ephemeris DE431, the same kernel Solar Fire and Astro Gold use. Because the south node is by definition the opposition of the north node, it's computed in the same step. Absolute positions match to the arc-second.
Astrolium supports 4 house systems — Placidus, Whole Sign, Koch, Equal. Whole-sign is the convention for traditional readings of the nodes; quadrant systems give different cusp-edge behavior. Switch from the dropdown without re-entering birth data.
Use the south node in your client work
Three contexts where the south node carries the reading.
When a client describes a recurring pattern — same kind of partner, same kind of work crisis, same family role — the south node's house and sign often name the loop directly. The framing is gentle: this is what the chart already knows how to do. The question is whether it's still earning its keep. In synastry, check the south node against a partner's planets; the synastry calculator shows how the inter-aspects engage the axis.
When the client's chart has heavy aspects to the south node — Saturn conjunct south node, Pluto squaring the axis — the pattern is structural rather than circumstantial. These charts often have a clearer sense of what they're leaving behind than what they're moving toward.
When transits or progressions cross the south node — eclipses are the classic trigger — the reading is about release rather than acquisition. Pair this with the predictive timing feature to see when the next nodal eclipse lands on your client's axis.
After the calculator
The nodes don't read in isolation. The ruler of the sign holding the south node — its placement, its aspects, its current transits — carries half the story. Eclipses on the axis change the timing. The natal aspects from other planets describe the texture.
For the structured way to read the south node inside the full chart, see the natal chart feature and the how to read a natal chart guide. For the growth-direction counterpart, see the north node calculator. For the asteroid points modern astrologers pair with the nodes, see the juno calculator and the lilith calculator.