Our Methodology

How HerbalCharts calculates your birth chart

HerbalCharts uses the True Sidereal zodiac with the Midpoint Method to calculate your birth chart based on the actual positions of the constellations in the sky.

True Sidereal Astrology

Unlike mainstream tropical astrology, which divides the zodiac into 12 equal 30-degree segments based on the seasons, True Sidereal astrology aligns with the real stars and constellations as they appear in the sky. This means each constellation has its actual size — Leo spans 38.42 degrees while Cancer covers just 17.15 degrees, reflecting the true geometry of the heavens.

True Sidereal also includes the 13th constellation, Ophiuchus, which sits between Scorpio and Sagittarius along the ecliptic. This constellation is visible in the sky and occupied by the Sun for approximately 12 days each year.

The Midpoint Method

The Midpoint Method defines constellation boundaries by calculating the midpoint between the last star of one constellation and the first star of the next, as measured along the ecliptic (the Sun's apparent path through the sky). This produces boundaries that are both astronomically grounded and astrologically meaningful.

For example, the boundary between Leo and Virgo is determined by finding the midpoint between Denebola (the last star of Leo) and Nu Virginis (the first star of Virgo) along the ecliptic. The constellation line stars are drawn from both Western (IAU) and Eastern (Vedic) traditions.

All boundary coordinates use the J2000 reference frame, a standard astronomical system that fixes star positions as they appeared on January 1, 2000. Adjustments for the Earth's axial precession are applied for each birth date.

Planetary Calculations

Planetary positions are calculated using the Swiss Ephemeris, a high-precision astronomical library used by professional astrologers and astronomers worldwide. It provides planetary longitudes accurate to within fractions of an arcsecond, based on the JPL Development Ephemeris (DE431) from NASA.

For each planet, we calculate its tropical ecliptic longitude and then convert it to the True Sidereal position using the Midpoint Method's ayanamsa (the angular offset between the tropical and sidereal zodiacs). The planet is then placed within its actual constellation based on the Midpoint boundaries.

Tropical System

HerbalCharts also supports the standard Western tropical zodiac for those who prefer it. The tropical system divides the ecliptic into 12 equal 30-degree signs starting from the vernal equinox (0 degrees Aries = the March equinox). No ayanamsa correction is applied in this mode.

Herbal Correspondences

Our herbal recommendations draw on centuries of traditional knowledge linking plants to planets and zodiac signs. The primary source is Nicholas Culpeper's Complete Herbal (1653), which systematically catalogued planetary rulerships for hundreds of herbs. Cell salt recommendations follow Dr. Wilhelm Schuessler's biochemic system of 12 tissue salts, each corresponding to a zodiac sign.

For more details on our sources, see our Credits & Sources page.

Credits