Method
The natal chart on this site is the result of a precise astronomical calculation, not a ready-made "horoscope from a table." Below is how the chart is built: what data it draws on, which astrological tradition it follows, and what it contains.
What the calculation is based on
The positions of the luminaries and planets are computed by our own astronomical engine, built on well-established astronomical models (VSOP87 and ELP2000) and data from NASA/JPL. In accuracy, these ephemerides (tables of celestial coordinates) are on a par with those used in professional astrology.
The calculation is accurate to within fractions of an arcsecond. For astrology this is more than enough: the error in a planet's position is negligible next to the width of a zodiac sign or a house. All coordinates are computed for the exact moment and place of birth, not averaged over a day or a year.
Which astrological tradition
The calculation follows Western tropical astrology, the most widely used astrological tradition. The zodiac is measured from the spring equinox (tropical, not sidereal), as is standard in the Western school.
The houses are calculated using the Placidus system, the most popular house system in Western astrology. In the rare case of a birth in high polar latitudes, where Placidus is mathematically unstable, the equal house system is used instead - a technical necessity, not a switch to a different tradition.
What the chart includes
The chart includes the ten luminaries and planets of classical astrology: the Sun, the Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. It also computes Chiron, the lunar nodes (North and South), and Lilith (the Black Moon) - points used in modern practice.
When the birth time is known, the chart is completed with the houses and the angles - the Ascendant and the Midheaven (MC) - along with the distribution of the planets across the twelve houses. Major aspects are calculated between the planets - conjunction, opposition, trine, square, and sextile - with orbs that depend on the importance of the bodies involved (wider for the luminaries, tighter for secondary points).
The role of birth time and place
An accurate birth time matters above all for the houses and the Ascendant: they shift by a whole sign in roughly two hours, and the Moon moves noticeably over the course of a day. If the time is unknown, the chart is still built - but without houses or the Ascendant, and the Moon's position and any signs near a day boundary are marked as approximate.
The place of birth determines the geographic coordinates and the time zone. The city is selected from the GeoNames database, which supplies the latitude, longitude, and time zone - which is why it is important to choose the correct location.
Disclaimer
Astrology is a tool for self-reflection, self-knowledge, and curiosity. It is not a scientific method: its claims are not confirmed by the natural sciences, and a natal chart does not predict events or determine fate.
A chart is best taken as an invitation to think about yourself, not as a set of instructions. It is no substitute for professional advice - from a doctor, psychologist, lawyer, or financial adviser. Make any important decisions about your health, relationships, money, or career with professional help and your own good sense.
Frequently asked questions about the method
Which zodiac is used - tropical or sidereal?
The tropical zodiac, measured from the spring equinox. This is the standard of Western astrology. The sidereal zodiac (used in the Vedic tradition) produces different sign positions and is not used here.
Which house system is used?
The Placidus system, the most widely used in Western astrology. In high polar latitudes, where Placidus becomes unstable, the equal house system is applied automatically.
Can a chart be built without a birth time?
Yes. Without a birth time, the chart is built from the planets' positions in the signs, but without houses, the Ascendant, or the MC. The Moon's position and any signs near a day boundary are then marked as approximate.
How accurate are the calculations?
The astronomical accuracy is on the order of fractions of an arcsecond: the calculation is run by our own high-precision astronomical engine. This is far more precise than astrological interpretation requires.