Lilith, mean and true: why they disagree

Lilith · mean cycle about 9 years · mean and true can differ by up to about 10° · both shown on the wheel

01A point, not a planet

Black Moon Lilith has no mass, no orbit of its own around the Sun, and no physical location in space to point a telescope at. It is a mathematically defined point in the geometry of the Moon's orbit around Earth: specifically, the empty focus of the ellipse the Moon traces — every ellipse has two foci, and while Earth sits at one of them, nothing occupies the other. Lilith is that second, empty focus, projected onto the sky as if something were there. It is closer in kind to the lunar nodes — geometric intersections rather than bodies — than it is to any planet, and like the nodes it is computed rather than observed.

The engine's own naming is more literal than the mythic label suggests. Swiss Ephemeris designates the two variants as the mean and osculating lunar apogee — the apogee being the point along an orbit farthest from the body it circles. Earth, the empty focus, and both apses of the Moon's ellipse all sit on the same straight line running through the orbit, so the direction toward that empty focus and the direction toward the apogee are the same direction as seen from Earth. "Lilith" is the astrological name; "apogee" is the orbital-mechanics description of the same point, and the engine's internal identifiers use the second.

The Moon's orbit is not a fixed ellipse sitting still in space; the ellipse itself slowly rotates, carried around by the pull of the Sun and Earth's other perturbations, and that rotation is what gives Lilith its own cycle: about nine years to complete a full lap of the zodiac, several times faster than the roughly eighteen-and-a-half-year cycle that governs the lunar nodes' own slow regression. Nine years for one point, eighteen and a half for the other — different mechanisms, moving at different rates, and easy to conflate only because both are computed points rather than visible bodies.

The nine-year figure belongs to the mean point specifically, the one built from the smoothed, idealized version of the orbit. It is a useful number for orientation — roughly how long Lilith takes to visit every sign once, at about nine months a sign on average — but it describes a steady average rather than the true point's actual pace on any given week, which is the whole subject of the next section.

02Two ways to compute the same idea

The ambiguity starts with a genuine choice in the arithmetic, not a disagreement about the underlying astronomy. The Moon's real path around Earth is not the smooth, idealized ellipse used in a textbook diagram — it is constantly perturbed by the Sun's gravity, which means the ellipse's shape and orientation are shifting in small ways all the time, not just in the one slow, steady rotation that defines Lilith's average cycle. There are, as a result, two different ellipses a calculation can use, and each gives a different empty focus.

The mean value smooths all of that away: it uses an idealized, averaged version of the Moon's orbit, which rotates at a constant, predictable rate and produces a Lilith that moves smoothly and monotonically through the zodiac, with no backward loops and no sudden jumps — Lizastro computes this as the mean apogee. The true, or osculating, value drops the smoothing and uses the Moon's actual, perturbed path at each instant, which means it tracks the real, wobbling orbit rather than the tidy average — and because the real orbit is not tidy, the true Lilith does not move smoothly either. It can accelerate, slow down, and briefly loop back on itself in ways the mean point never does, because it is following the Moon's actual irregular path rather than a mathematical idealization of it.

Both are legitimate answers to the same geometric question, computed from the same ephemeris, and neither is a rounding error of the other. They are two different, equally rigorous definitions of "the empty focus of the Moon's orbit," and they diverge because the Moon's real orbit and the idealized average of it are not the same curve.

The lunar nodes go through a version of the same split, for the same underlying reason — a mean value built from the smoothed average orbit, and a true value that tracks the Moon's actual, perturbed path — and the two follow a similar shape of relationship in both cases: the mean point advances or regresses at a constant, predictable pace, while the true point wanders around that steady baseline, sometimes ahead of it and sometimes behind, occasionally even reversing its own direction of travel briefly before rejoining the general trend. The two computed-point pairs in a Lizastro chart, Lilith and the nodes, are built from the same kind of choice between a smoothed model and the actual perturbed orbit — which is also why a reader who understands one pair has already done most of the work of understanding the other.

03How far apart, and what that does

At a given moment, the mean and true positions can sit up to about ten degrees apart — enough, depending on exactly where each one falls, to land in different signs, different houses, or on opposite sides of a chart's angles entirely. That is not a small rounding difference tucked away at the edge of precision; it is large enough that a reading built on one variant and a reading built on the other can genuinely disagree about which sign or house is involved, which is exactly why the distinction is worth stating rather than picking one silently and hoping nobody asks.

Because both are computed from the same underlying lunar theory, they are not simply two competing opinions about where Lilith "really" is — they are two different, equally well-defined quantities that happen to share a name. Software that reports only one, without saying which, is not being more decisive than software that reports both; it is making an invisible choice on the reader's behalf and calling the result Lilith without qualification.

The practical effect scales with how far apart the two happen to fall on a given date, which is not constant — sometimes the mean and true points are close, sometimes they are near the maximum separation. A degree or two of difference rarely changes which sign or house is involved. Several degrees can, particularly for a placement that already sits close to a sign or house boundary under either calculation, which is exactly the situation where naming both variants instead of picking one quietly matters most.

04What it is not

Lilith is not the same object as 1181 Lilith, a numbered minor planet discovered in 1927 that some software computes and displays under the same name. That asteroid has mass, an orbit around the Sun, and a physical existence that Black Moon Lilith, a calculated point rather than a body, simply does not have — the shared name is a historical accident, not a sign that two calculations are approximating the same thing. Confusing the two is an easy mistake to make and a real source of disagreement between different pieces of software that has nothing to do with mean versus true at all.

Neither is "the real Lilith" and the other an approximation of it worth discarding. Different schools of astrology have settled on different defaults for reasons of tradition rather than one variant being demonstrably more accurate than the other, and a product that quietly picks one and hides the disagreement is making an editorial choice while presenting it as a neutral fact. Lilith also is not, mechanically, a claim about "the wound of womanhood" or a specific mythic narrative grafted onto a geometry lesson — that reading is cultural weight added after the fact to a point whose actual definition is an empty ellipse focus. What the placement more plainly describes, independent of any myth attached to it, is a tendency toward refusal: a part of a chart associated with declining to be managed, and with choosing exclusion over convenient compromise. That is a tendency to read like any other placement, not a verdict about gender or trauma.

05Where you see it in your own chart

Both variants are placed on a Lizastro chart with their own sign, house, and exact degree, rather than one being computed and the other left out. If the two sit close together for a given birth date, the choice barely matters for that particular chart. If they sit far apart — toward that roughly ten-degree maximum — they can disagree about which house or even which sign is involved, and the honest response to that is to look at both rather than to trust whichever one a given piece of software happened to default to.

Neither variant is held back behind a paywall or trimmed out of the free chart to be sold separately later. Both come from the same ephemeris call that produces every other placement, at no extra computational cost, which is also true of the lunar nodes and Chiron — the extended points that most consumer astrology software either hides or omits, shown here because there is no reason built into the calculation to withhold them.

→ See both variants on your chart

06Related reading

Scorpio is the sign most often paired with Lilith in practice, and for a related reason: it is also where Lizastro's rulership dispute lives, between Mars and Pluto, and both pieces exist because the product's position is to show a genuine disagreement rather than resolve it for the reader. The lunar nodes are the other computed-point pair in the chart, with the same mean-versus-true structure and a very different cycle length.

Updated 2026-08-19.