Our Methodology
We use the same astronomical calculations trusted by observatories and space agencies worldwide.
VSOP87 Ephemeris
The Gold Standard in Planetary Position Calculations
VSOP87 (Variations Séculaires des Orbites Planétaires) is a mathematical model developed by the Bureau des Longitudes in Paris. It calculates planetary positions with exceptional accuracy by modeling the gravitational interactions between all planets in our solar system.
This is the same calculation method used by NASA's Jet Propulsion Laboratory, major observatories, and professional astronomical software. When we say 'observatory-grade precision,' we mean it literally.
How We Calculate Your Chart
Time Conversion
We convert your birth date, time, and timezone to Julian Date—the standard astronomical time format that accounts for leap years, timezone changes, and historical calendar adjustments.
Planetary Positions
Using VSOP87 algorithms, we calculate the precise ecliptic longitude of each planet at your birth moment. This includes the Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
House Cusps & Angles
Based on your birth location's latitude and local sidereal time, we calculate house cusps, Ascendant, Midheaven, and Vertex using the Placidus house system (the most widely used in Western astrology). We support 10 house systems total.
Aspect Calculation
We identify geometric relationships between planets (conjunctions, oppositions, trines, squares, sextiles) and calculate their orbs for precise aspect interpretation.
Verification Process
We don't just trust our calculations—we verify them.
All planetary positions are cross-checked against astro.com, the industry standard for professional astrologers.
We maintain a test suite of celebrity charts with verified birth times, ensuring every calculation matches within 2 arc-minutes.
Our calculations are updated regularly to account for the latest astronomical constants and corrections.
Accuracy Guarantees
Our commitment to precision means you can trust every position in your chart.
Related Resources
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