Planetary Nodes & Apsides #

The PlanetaryNodesFactory calculates orbital nodes (where the orbit crosses the ecliptic) and apsides (the closest and farthest points of the orbit) for any planet, and for the Moon.

Concepts #

• Ascending Node: where the orbit crosses the ecliptic northward
• Descending Node: where the orbit crosses the ecliptic southward
• Periapsis: closest point of the orbit to the body it goes round
• Apoapsis: farthest point of the orbit from that body

The apsides are exposed under two pairs of names holding the same two points. periapsis / apoapsis are generic and always correct. perihelion / aphelion are the older fields, deprecated: they name the Sun, which is right for the eight planets and wrong for the Moon, which goes round the Earth. They are still populated with the very same objects, so the two names can never drift apart and nothing that reads them breaks.

apsis_kind says which reading applies: "heliocentric" for every planet, "geocentric" for the Moon alone. The Moon’s apsides are the perigee and the apogee, and the far one is to the decimal the point the tradition calls the Black Moon Lilith — mean_lilith with method="mean", true_lilith with method="osculating".

Two calculation methods are available:

• Mean: average orbital elements (smoother, used for long-term analysis)
• Osculating: instantaneous orbital elements (more precise for a given moment)

Basic Usage #

from kerykeion import AstrologicalSubjectFactory, PlanetaryNodesFactory

subject = AstrologicalSubjectFactory.from_birth_data(
    "John", 1990, 6, 15, 14, 30,
    lng=12.5, lat=41.9, tz_str="Europe/Rome", online=False,
)

results = PlanetaryNodesFactory.from_subject(subject, method="mean")

for node in results.nodes:
    print(f"\n{node.planet_name}:")
    print(f"  Ascending Node:  {node.ascending_node.sign} {node.ascending_node.position:.2f}")
    print(f"  Descending Node: {node.descending_node.sign} {node.descending_node.position:.2f}")
    print(f"  Periapsis:       {node.periapsis.sign} {node.periapsis.position:.2f}")
    print(f"  Apoapsis:        {node.apoapsis.sign} {node.apoapsis.position:.2f} ({node.apsis_kind})")

The Moon’s apogee and the Black Moon Lilith are one point:

from kerykeion import AstrologicalSubjectFactory, PlanetaryNodesFactory

subject = AstrologicalSubjectFactory.from_birth_data(
    "John", 1990, 6, 15, 14, 30,
    lng=12.5, lat=41.9, tz_str="Europe/Rome", online=False,
    active_points=["Sun", "Moon", "Mean_Lilith"],
)
moon = PlanetaryNodesFactory.from_subject(subject, method="mean", planets=["Moon"]).nodes[0]
print(moon.apsis_kind)                                       # geocentric
print(moon.apoapsis.abs_pos == subject.mean_lilith.abs_pos)   # True

Methods #

from_subject(subject, method, planets) #

Calculate nodes from an existing astrological subject.

The node and apsis longitudes – and the sign metadata derived from them – are computed in the subject’s own zodiac frame: a sidereal subject gets sidereal longitudes, consistent with the rest of its chart.

Returns: PlanetaryNodesCollectionModel

from_julian_day(julian_day, method, planets) #

Calculate nodes from a Julian Day number. A bare instant carries no zodiac frame, so the longitudes are always tropical – pass a subject to from_subject when sidereal ones are wanted.

Returns: PlanetaryNodesCollectionModel

Data Models #

PlanetaryNodeModel #

PlanetaryNodesCollectionModel #

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