Astro Natal Chart

Calculates and interprets the natal chart by date, time and place of birth with the positions of planets, houses and main aspects.

Astrology — Natal Chart

Engine: Swiss Ephemeris (pyswisseph 2.10.3.2)

This skill uses pyswisseph 2.10.3.2, the Python binding for the Swiss Ephemeris — the gold standard of astrological computation.

Why Swiss Ephemeris?

Compared to simplified formulas (e.g., Meeus approximations or fixed-position lookup tables):

Feature	Simplified formulas	Swiss Ephemeris (pyswisseph)
Source data	Mathematical approximations	NASA JPL DE431 ephemerides
Sun accuracy	~0.5–1°	~0.001°
Moon accuracy	~1–5°	~0.005°
Planet accuracy	~1–15° (outer planets)	~0.003°
House system	Often Static Equal / Whole Sign	Iterative Placidus (swe.houses_ex)
Retrograde detection	Basic sign-based	Precise velocity (FLG_SPEED)
Time coverage	Limited (~0–3000 AD)	13201 BC – AD 17191
Computation	Analytical approx.	Numerical integration

In practice this means:

• Outer planets (Uranus, Neptune, Pluto) — simplified formulas can be off by 10–15°, Swiss Ephemeris keeps error within 0.003°
• Moon position — up to 5° error vs 0.005° with SWE
• House cusps — iterative Placidus gives exact critical-point cusps, unlike analytical approximations
• Retrograde — detected from true velocity sign, not interpolated

Library info

• Package: pyswisseph v2.10.3.2 (build 20230604)
• License: AGPL-3.0 (commercial use permitted with open-source compliance; otherwise GPL-2.0)
• The .pyd file is bundled locally in scripts/ — no system-wide installation needed
• No external dependencies — libswe and sqlite3 are compiled into the .pyd; works out of the box on Python 3.10+
• Windows .pyd compiled with MSVC 14.44 (Build Tools 2022), tested with Python 3.14.5

Input Parameters

1. Birth date — DD.MM.YYYY
2. Birth time — HH:MM (local time)
3. Birth place — city name

If the birth time is unknown, use 12:00 (noon), but warn the user that house cusps and ASC will be approximate.

Calculation Algorithm

1. Determine city coordinates from the built-in database (50+ cities)
2. Determine timezone and UTC offset
3. Convert local time to UTC, then to Julian Day via swe.julday()
4. Calculate all planets via swe.calc_ut() with FLG_SWIEPH | FLG_SPEED
5. Calculate house cusps via swe.houses_ex() (Placidus system)
6. Calculate aspects (conjunction, opposition, trine, square, sextile, and minor)
7. Generate interpretation

Execution

python scripts/natal_chart_swe.py 24.04.1983 06:00 Ижевск

Output Format

🌟 NATAL CHART  [Swiss Ephemeris vX.XX]
📅 Date: [date]  ⏰ Time: [time]  📍 Place: [city]
🌍 Coordinates: [lat], [lon]  🕐 Timezone: [tz] (UTC+/-offset)
📊 JD: [julian_day]

⬆️ ASC — [sign] [degrees]′
🜨 MC — [sign] [degrees]′

PLANETS:
☀️ Sun — [sign] [degrees]′ [house] [℞] (speed °/day)
🌙 Moon — [sign] [degrees]′ [house]
☿ Mercury — [sign] [degrees]′ [house]
♀ Venus — [sign] [degrees]′ [house]
♂ Mars — [sign] [degrees]′ [house] [℞]
♃ Jupiter — [sign] [degrees]′ [house] [℞]
♄ Saturn — [sign] [degrees]′ [house] [℞]
♅ Uranus — [sign] [degrees]′ [house] [℞]
♆ Neptune — [sign] [degrees]′ [house] [℞]
♇ Pluto — [sign] [degrees]′ [house] [℞]

HOUSES:
I house — [sign] [degrees]′
... (all 12 houses)

MAJOR ASPECTS:
☌ Conjunction: [planet]-[planet] (orb: X.X°)
□ Square: [planet]-[planet] (orb: X.X°)
△ Trine: [planet]-[planet] (orb: X.X°)
☍ Opposition: [planet]-[planet] (orb: X.X°)
✶ Sextile: [planet]-[planet] (orb: X.X°)

INTERPRETATION:
[detailed interpretation]

Aspect Orbs

Aspect	Symbol	Orb
Conjunction	☌	±8°
Opposition	☍	±8°
Square	□	±7°
Trine	△	±7°
Sextile	✶	±5°
Semisextile	⚺	±2°
Quincunx	⚹	±2°
Semisquare	∠	±2°

Zodiac Signs — Keywords

• ♈ Aries: initiative, energy, impulsiveness
• ♉ Taurus: stability, sensuality, stubbornness
• ♊ Gemini: sociability, intellect, curiosity
• ♋ Cancer: emotionality, nurturing, intuition
• ♌ Leo: creativity, leadership, pride
• ♍ Virgo: analytical, practical, perfectionist
• ♎ Libra: harmony, diplomacy, partnership
• ♏ Scorpio: depth, transformation, intensity
• ♐ Sagittarius: optimism, philosophy, freedom
• ♑ Capricorn: ambition, discipline, responsibility
• ♒ Aquarius: originality, independence, innovation
• ♓ Pisces: intuition, compassion, dreaminess

Planets — Meanings

• Sun — ego, essence, vitality, father
• Moon — emotions, subconscious, mother, instincts
• Mercury — thinking, communication, learning
• Venus — love, beauty, values, finances
• Mars — energy, action, aggression, sexuality
• Jupiter — expansion, luck, wisdom, growth
• Saturn — limitations, discipline, karma, structure
• Uranus — change, rebellion, innovation, suddenness
• Neptune — illusion, spirituality, creativity, dissolution
• Pluto — transformation, power, death/rebirth

Houses — Life Areas

1. I (ASC) — personality, appearance, self-presentation
2. II — money, values, resources
3. III — communication, siblings, learning
4. IV (IC) — home, family, roots
5. V — creativity, children, romance
6. VI — health, work, routine
7. VII (DSC) — partnership, marriage
8. VIII — transformation, shared resources, intimacy
9. IX — philosophy, travel, higher education
10. X (MC) — career, reputation, goals
11. XI — friends, hopes, groups
12. XII — solitude, subconscious, karma

Interpretation Guidelines

When interpreting, consider:

1. Sun — core personality
2. Moon — emotional nature
3. Ascendant — mask, first impression
4. MC — career aspirations
5. Stelliums (3+ planets in one sign/house)
6. Retrograde planets — energy turned inward
7. Major aspects — personality dynamics
8. Dominant elements (fire, earth, air, water)

Disclaimer

This is an entertainment/educational tool, not a scientific method. Do not make medical or financial predictions based on astrological readings.

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Changelog

v2.0.0 (2026-05-28)

• Switched to Swiss Ephemeris (pyswisseph 2.10.3.2) as the primary calculation engine — replaces simplified analytical formulas
• Replaced swe.JUPITER hardcoded positions with swe.calc_ut() using NASA JPL DE431 ephemerides
• House calculation now uses swe.houses_ex() (exact iterative Placidus) instead of analytical approximations
• Added retrograde detection via FLG_SPEED flag (velocity sign)
• Bundled swisseph.cp314-win_amd64.pyd (2 MB) in scripts/ — no system-wide installation required
• Version detection: swe.__version__ returns int 20230604 — formatted as vYY.MM.BLD string
• Expanded city database to 50+ cities with coordinates and timezone data
• Added proper Julian Day conversion through swe.julday()
• Removed legacy scripts: natal_chart.py, placidus_iterative.py, placidus_meeus.py and all debug/fix scripts (11 files)
• SKILL.md rewritten in English with full documentation

v1.x (earlier)

• Initial release using simplified analytical formulas
• Separate iterative and Meeus-based Placidus implementations
• Planet positions calculated with approximate algorithms (0.5–15° error range)