How We Calculate Birth Charts: Method and Limitations
Doğum Harita calculates celestial placements from a birth instant and location. These steps describe the method used by this website and distinguish astronomical positions from their symbolic astrological meanings.
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Planetary positions are calculated astronomically. Astrological meanings are symbolic interpretations, not scientific personality tests or predictions of future events.
1. Turning a birthplace into coordinates
Place searches use Nominatim with OpenStreetMap data to obtain latitude and longitude. Check the region and country because places can share names. A city or district centre is not necessarily the exact birth address. The place search sends the location query and language, not the person’s name or birth date.
2. Converting local time to UTC
The coordinates identify a time zone. Luxon converts the birth date and local clock time to UTC using historical time-zone rules. Do not add today’s UTC offset manually. When clocks move backwards a local time may occur twice; when they move forwards a time may not exist. Check the original record and time zone carefully for those dates.
3. Calculating positions and houses
The UTC instant becomes a Julian day for the Swiss Ephemeris-based calculation engine. Longitudes are assigned to signs in the default tropical zodiac; houses use Placidus. The ascendant, Midheaven, planetary positions and twelve house cusps are displayed separately. This version does not offer a sidereal zodiac or alternative house-system selector. Match these settings when comparing another tool.
4. Degrees, retrograde motion and saved results
Positions within a sign are displayed in degrees, minutes and seconds. A negative longitudinal speed produces the retrograde label. The calculation is saved with a result link. Displaying seconds of arc does not establish that the birth time is known to the second or guarantee equivalent accuracy. Input uncertainty particularly affects the ascendant and house cusps.
Limitations and checking a result
The wrong city, an approximate time, historical time records and high latitudes can affect results. Placidus has limitations in polar regions. This method is not a personality diagnosis, health assessment or certain prediction. Check the inputs before comparing an independent calculation with matching zodiac and house settings. Our guides explain the interface and method; we do not present them as having received expert review.