House Systems #

Kerykeion supports 23 different house systems (Swiss Ephemeris letter codes, honoured by both backends). Each system divides the celestial sphere differently, affecting house cusp positions (though planetary positions remain the same).

Choosing a House System #

The choice of house system depends on your astrological tradition and preferences:

• Modern Western: Placidus (default) or Koch
• Traditional/Hellenistic: Whole Sign or Porphyry
• Medieval: Regiomontanus or Alcabitius
• Vedic/Jyotish: Whole Sign or Sripati
• Horary: Regiomontanus
• Inside the polar circle: Whole Sign, Equal or Porphyry — the quadrant systems are undefined there and Kerykeion substitutes one for them (see below)

Complete House Systems Reference #

Examples #

Birth Chart with Morinus House System #

from pathlib import Path
from kerykeion import AstrologicalSubjectFactory
from kerykeion.chart_data.factory import ChartDataFactory
from kerykeion.charts.drawer import ChartDrawer

morinus_subject = AstrologicalSubjectFactory.from_birth_data(
    "John Lennon - House System Morinus", 1940, 10, 9, 18, 30,
    lng=-2.9833, lat=53.4, tz_str="Europe/London",
    online=False,
    houses_system_identifier="M",
)
data = ChartDataFactory.create_natal_chart_data(morinus_subject)
chart = ChartDrawer(data)

out_dir = Path("charts_output")
out_dir.mkdir(exist_ok=True)
chart.save_svg(output_path=out_dir, filename="john-lennon-morinus", style="classic")

The output will be:

Birth Chart with Whole Sign Houses #

from pathlib import Path
from kerykeion import AstrologicalSubjectFactory
from kerykeion.chart_data.factory import ChartDataFactory
from kerykeion.charts.drawer import ChartDrawer

whole_sign_subject = AstrologicalSubjectFactory.from_birth_data(
    "John Lennon - Whole Sign", 1940, 10, 9, 18, 30,
    lng=-2.9833, lat=53.4, tz_str="Europe/London",
    online=False,
    houses_system_identifier="W",
)
data = ChartDataFactory.create_natal_chart_data(whole_sign_subject)
chart = ChartDrawer(data)

out_dir = Path("charts_output")
out_dir.mkdir(exist_ok=True)
chart.save_svg(output_path=out_dir, filename="john-lennon-whole-sign")

Check House System Name on a Subject #

from kerykeion import AstrologicalSubjectFactory

subject = AstrologicalSubjectFactory.from_birth_data(
    "Johnny Depp", 1963, 6, 9, 0, 0,
    lng=-87.1112,
    lat=37.7719,
    tz_str="America/Chicago",
    online=False,
    houses_system_identifier="P",  # Placidus
)

print(subject.houses_system_name)
# Output: Placidus

Comparing House Systems #

from kerykeion import AstrologicalSubjectFactory

# Same birth data, different house systems
systems = {"P": "Placidus", "K": "Koch", "W": "Whole Sign", "R": "Regiomontanus"}

for system_id, label in systems.items():
    subject = AstrologicalSubjectFactory.from_birth_data(
        "Test", 1990, 6, 15, 12, 0,
        lng=-0.1276, lat=51.5074, tz_str="Europe/London",
        online=False,
        houses_system_identifier=system_id,
    )
    print(f"{label}:")
    print(f"  1st House: {subject.first_house.sign} {subject.first_house.position:.1f}°")
    print(f"  10th House (MC): {subject.tenth_house.sign} {subject.tenth_house.position:.1f}°")

Output:

Placidus:
  1st House: Vir 14.7°
  10th House (MC): Gem 10.0°
Koch:
  1st House: Vir 14.7°
  10th House (MC): Gem 10.0°
Whole Sign:
  1st House: Vir 0.0°
  10th House (MC): Gem 0.0°
Regiomontanus:
  1st House: Vir 14.7°
  10th House (MC): Gem 10.0°

Note: The Ascendant and MC remain the same across most systems - only the intermediate house cusps differ.

Inside the Polar Circle #

A quadrant system divides the semi-diurnal arc of a degree of the ecliptic. Inside the polar circle some degrees never rise or set, so that arc does not exist and there is nothing to divide. Kerykeion does not fail there, and does not move the observer either: it recomputes the cusps with Porphyry ("O") at the real latitude, logs a warning naming both systems, and records the substitution.

from kerykeion import AstrologicalSubjectFactory

subject = AstrologicalSubjectFactory.from_birth_data(
    "Arctic Explorer", 1990, 6, 21, 12, 0,
    lng=25.0, lat=70.0, tz_str="Europe/Helsinki", online=False,
    houses_system_identifier="P",
)

print(subject.lat)                                 # 70.0  — never clamped
print(subject.houses_system_identifier)            # "P"   — what you asked for
print(subject.effective_houses_system_identifier)  # "O"   — what the cusps used
print(subject.polar_house_fallbacks[0].affects)    # ["house_cusps"]

The angles are untouched: the Ascendant, MC, Descendant, IC and Vertex are intersections of the ecliptic with the horizon and the meridian, so they do not depend on a house system and stay exact at any latitude. Pick "W" or "A" if you would rather choose the division yourself than accept a substitute.

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