Calculated Points in Astrology

What are calculated points?

Planets and asteroids are physical objects moving through space. Calculated points are different: there is no physical object located at the degree shown in the natal chart.

Instead, their positions are produced by applying an astronomical or mathematical rule.

Some calculated points come from real orbital geometry. The Lunar Nodes and Black Moon Lilith are examples. Others, such as the Part of Fortune, are created by combining chart positions through a formula.

The Lunar Nodes

The North Node and South Node are the two places where the Moon's orbit crosses the apparent path of the Sun around the Earth, known as the ecliptic.

The Moon's orbit is tilted by approximately five degrees relative to the ecliptic. Because the two orbital paths are not on exactly the same plane, they intersect at two opposite points.

The Nodes are always directly opposite each other in the zodiac. If the North Node is at 12 degrees Aries, the South Node is at 12 degrees Libra.

How are the Lunar Nodes calculated?

Imagine two slightly tilted rings crossing each other. One ring represents the ecliptic and the other represents the Moon's orbit.

The two places where those rings cross are the Lunar Nodes. Astrology software calculates where those crossings fall within the zodiac at a particular moment.

K The North Node

In modern astrology, the North Node is commonly associated with development, unfamiliar experiences and qualities that a person is encouraged to cultivate.

It may describe a direction of growth that initially feels less automatic than the South Node. This does not mean that the North Node guarantees success or that a person must abandon everything represented by the South Node.

The sign of the North Node describes the qualities being developed, while its house indicates the area of life in which that development may occur.

L The South Node

The South Node is commonly associated with familiar habits, established abilities and ways of responding that feel natural or automatic.

Some traditions connect it with the past or previous lives. These interpretations are spiritual beliefs and cannot be demonstrated from the astronomical calculation itself.

A balanced interpretation does not treat the South Node as something negative that must be rejected. Its existing strengths can support movement toward the North Node.

M Black Moon Lilith

Black Moon Lilith is not a planet, moon or asteroid. It is a calculated position connected with the Moon's elliptical orbit around the Earth.

The Moon does not travel around Earth in a perfect circle. Its orbit is shaped more like a stretched circle, called an ellipse.

Earth is not located exactly at the centre of this ellipse. The point of the Moon's orbit furthest from Earth is called the lunar apogee. Black Moon Lilith is based on this orbital point.

Astrologically, Lilith is often associated with independence, rejection, instinct, taboo subjects, suppressed anger and parts of the self that resist control or social approval.

How is Black Moon Lilith calculated?

Imagine the Moon's orbit as an oval with Earth positioned away from its centre.

One end of the oval is closer to Earth and is called the perigee. The opposite end is further away and is called the apogee.

As with the Lunar Nodes, more than one Lilith calculation may appear in astrology software:

These calculations can produce different degrees, which explains why two astrology programs may show different Lilith positions without either program necessarily being broken.

v The Vertex

The Vertex is a calculated point found on the western side of the natal chart. It is created by the intersection of the ecliptic with the prime vertical.

The prime vertical is an imaginary circle passing through the east point, the point directly overhead, the west point and the point directly beneath the observer. The ecliptic is the apparent path of the Sun through the zodiac.

Where these two astronomical circles intersect on the western side of the chart, astrology identifies the Vertex. The opposite point is called the Anti-Vertex.

In modern astrology, the Vertex is often associated with encounters or circumstances that feel significant, unexpected or outside a person's direct control.

It is particularly popular in relationship astrology. A planet in one person's chart closely conjunct another person's Vertex may be interpreted as indicating a meaningful connection or an encounter that strongly affects both people.

How is the Vertex calculated?

The Vertex depends on the exact birth time and geographical location. It cannot be calculated reliably from the birth date alone.

In simple terms, astrology software builds two imaginary circles around the observer:

• the ecliptic, which contains the zodiac;
• the prime vertical, which runs through the east, overhead, west and below the observer.

The program then finds where those circles cross on the western side of the chart.

Because the orientation of these circles changes as the Earth rotates, even a modest change in birth time can move the Vertex noticeably.

Its zodiac sign describes the style associated with the point, while its house position indicates the area of life in which Vertex-related encounters or turning points may be interpreted.

N The Part of Fortune

The Part of Fortune, also called the Lot of Fortune, is a mathematical point created from the Ascendant, Sun and Moon.

It is not an object in space. It belongs to a larger family of calculated positions historically known as the Arabic Parts or Lots.

Astrologically, the Part of Fortune is commonly associated with material circumstances, wellbeing, natural flow, prosperity and the ways the Sun, Moon and Ascendant work together.

Its sign describes how the Fortune principle may be expressed, while its house describes the area of life in which it may become most noticeable.

How is the Part of Fortune calculated?

Every position in the zodiac can be converted into a number from 0 to 360 degrees:

• 0° Aries becomes 0°;
• 0° Taurus becomes 30°;
• 0° Gemini becomes 60°;
• 0° Cancer becomes 90°;
• and so on through the zodiac.

The calculation then adds two positions and subtracts another.

In simple terms, the formula measures the distance between the Sun and Moon and projects that distance from the Ascendant.

A simplified example

Suppose a day chart has:

• Ascendant at 10° Aries, equal to 10°;
• Moon at 20° Gemini, equal to 80°;
• Sun at 5° Taurus, equal to 35°.

When a result is greater than 360°, subtract 360°. When it is below 0°, add 360°. This brings the result back inside the zodiac circle.

Arabic Parts and Lots

The Part of Fortune is only one member of a much larger group of calculated points. They are commonly called Arabic Parts because medieval Arabic-speaking astrologers preserved, developed and transmitted many of their formulas.

They are also called Lots, particularly when discussing Hellenistic astrology. Their history predates medieval Arabic astrology, so the name Lots is often more historically precise.

A Lot normally follows this pattern:

There are many more Lots associated with marriage, parents, children, travel, illness, property, career and other subjects.

Formula names and calculations vary between authors, historical periods and astrological traditions. Therefore, a formula should always be identified with its source rather than presented as the only possible version.

How important are calculated points?

Calculated points are normally interpreted after the main structure of the natal chart has been understood.

Begin with:

• the Sun and Moon;
• the planets;
• the Ascendant and Midheaven;
• the houses and their rulers;
• the major aspects.

The Nodes, Lilith, Fortune and other Lots can then refine or reinforce themes already visible in the chart.

A calculated point is usually more noticeable when it is:

• closely conjunct the Sun or Moon;
• close to the Ascendant or Midheaven;
• closely aspecting a personal planet;
• connected with the ruler of an important house;
• repeating a theme found elsewhere in the chart.