How We Calculate Your Chart
Natal Echo uses its own astrology engine to calculate charts from a birth moment and location. The astronomical calculation and the meaning assigned to it are separate layers.
Our Calculation Engine
Production chart calculations come from our astro_api service. The main planetary models use analytical ephemeris calculations, including VSOP87 series for planetary motion. We use independent reference calculations in development checks; those reference tools are not a replacement for our engine.
Selected planetary positions and event times are compared against JPL Horizons reference results. Comparisons depend on the body, date, reference frame and time scale. A successful sample check does not establish one error bound for every body and date, and it is not a NASA certification of this service.
Positions displayed to a degree and minute are rounded output. Display precision is not a guarantee of numerical accuracy. Chiron, lunar nodes, planetary positions and event times have different model limitations.
Coordinates and Time
Our standard natal charts use the tropical zodiac and geocentric planetary positions. Geocentric means measured from the center of Earth; entering a birthplace does not by itself make those positions topocentric. The place and time are needed for the local horizon, Ascendant, Midheaven and house cusps.
Local birth times are converted to UTC using location and historical time-zone information. Daylight-saving changes can make a local time ambiguous or nonexistent. Check uncertain records and time-zone assumptions before treating the resulting angles as exact.
Houses and Polar Locations
Our default house calculation is Placidus. At polar locations where it cannot be calculated, the engine can return Porphyry houses and label the house system used. A near-cusp planet can change house when a different system or birth time is used.
Without a reliable birth time, the Ascendant, Midheaven and houses are uncertain. Even a planetary sign can be uncertain on a sign-ingress date. Check the whole possible birth interval rather than identifying the correct time from a personality description.
Aspects and Retrograde Motion
The reading engine measures true angular separation using both ecliptic longitude and latitude. Many astrology systems instead compare longitude alone. The two measurements can produce different orbs, especially when a planet has substantial latitude. Poster and preview displays can apply different visual filters.
An aspect requires an explicit target angle and orb limit. A sign-based trine is not automatically a measured trine within an orb. Retrograde motion is determined from changes in geocentric ecliptic longitude over time; exact station times also depend on the numerical method and model.
Interpretations and Editorial Checks
Article examples can demonstrate calculated degrees, house membership and angular separations for stated inputs. They do not establish personality traits, medical risks, financial outcomes or the probability that a relationship will succeed.
Natal Echo Editorial Team is our collective publishing identity. It identifies the team responsible for our articles, not an individual astrologer or an independent scientific reviewer.
We use AI assistance in producing interpretations and articles. The Natal Echo team is responsible for checking factual claims, calculation examples and sources. Content review is ongoing. A page marked Last updated records a modification date, not a claim that a named expert has reviewed it.
If you find a calculation discrepancy, include the UTC time or original local time and time zone, coordinates, body, house system and coordinate convention when comparing results. For a factual article issue, identify the specific passage and its source so it can be checked.