How We Calculate Your Chart

Aurathea uses the Swiss Ephemeris, the gold standard for astronomical calculations in astrology software. Our data comes from NASA's JPL Development Ephemeris (DE441), providing planetary positions accurate to fractions of an arc-second. Coverage spans from 13,000 BC to 17,000 AD, ensuring accuracy for any birth date you might need.

We support 20 different house systems to accommodate all astrological traditions. Placidus is our default (the most widely used in Western astrology), but you can also use:

• Quadrant systems: Koch, Regiomontanus, Campanus, Porphyry, Morinus, Topocentric, Alcabitius
• Equal systems: Whole Sign, Equal (ASC), Equal (MC)
• Special systems: Horizon, Sripati, and more

Birth times are handled with full timezone awareness using the IANA timezone database—the same standard used by your phone and computer. Daylight Saving Time transitions are handled automatically, including historical changes. We support all global timezones from UTC-11 to UTC+14, covering every inhabited location on Earth.

Birth locations are resolved using a database of over 43,000 cities worldwide. Coordinates are stored with approximately 0.1-meter precision at the equator, ensuring accurate house cusp calculations even for locations near city boundaries. Our search is typo-tolerant and accent-normalized, so you can find your birthplace even if you're not sure of the exact spelling.

Our calculations meet or exceed professional standards:

• Planets: Positions accurate to 0.1 arc-minutes (6 arc-seconds)
• Moon: Position accurate to 0.5 arc-minutes due to its rapid movement
• House cusps: Calculated to the exact degree and minute
• Aspects: Traditional orbs with precise angular separation

We use the Tropical zodiac by default, which is standard in Western astrology. The Tropical zodiac is based on the seasons and the vernal equinox, not the physical constellations. For practitioners of Vedic astrology, we also support 9 sidereal ayanamsa options including Lahiri, Raman, and Krishnamurti.