The chart is calculated.
Not guessed.
NOEMA runs the astronomy in your browser. Your birth data does not need to be sent to a chart API.
Planetary positions
Sun, Moon and planetary positions are calculated with published orbital formulae designed for practical positional astronomy. The Moon includes the principal perturbation terms; Jupiter, Saturn and Uranus include their largest perturbations; Pluto uses a fitted heliocentric model. The supported range is 1800–2100.
Angles + houses
The Ascendant and Midheaven are calculated from Greenwich/local sidereal time, geographic latitude and the obliquity of the ecliptic. NOEMA currently offers Whole Sign and Equal House systems.
Timezones
The website ships with a local index of representative IANA timezone locations. Historical daylight-saving conversion is handled by the timezone data in your browser. If your birthplace is not listed, exact latitude, longitude and IANA timezone can be entered manually.
Astrocartography
MC/IC lines are calculated from each body's right ascension and Greenwich sidereal time. ASC/DSC curves are the geographic locations where that body was rising or setting at the birth moment.
Accuracy + limits
The engine is intended for natal-chart and reflective use, not spacecraft navigation. Planetary positions are typically far more precise than needed to determine zodiac signs; the Moon and fast-moving angles are the most sensitive to exact time. Birth years outside 1800–2100 and locations inside the polar circles are intentionally blocked.
Sources
The positional method follows the practical orbital formulae published by Paul Schlyter, which derive from Van Flandern & Pulkkinen-style algorithms; sidereal-time and angle calculations follow standard spherical astronomy. Map geometry uses Natural Earth. Timezone identifiers and historical offset rules use the IANA Time Zone Database available through the browser.