Vedic vs Western Astrology API: What's the Technical Difference?

The same person, born on the same date, gets a different Sun sign in Vedic vs Western astrology. This confuses users — and bugs developers who call the wrong endpoint. Here is exactly what is different and why.

The core difference: sidereal vs tropical zodiac

Western astrology uses the tropical zodiac— the zodiac is locked to Earth's seasons, so Aries always begins at the spring equinox (around March 21) regardless of where the stars actually are.

Vedic astrology uses the sidereal zodiac — the zodiac is locked to actual stellar positions. Due to the Earth's axial precession (a slow wobble), the two zodiacs have drifted ~23.8° apart since they aligned around 285 AD. This offset is called the ayanamsa.

Result: a person who is Libra in Western astrology is almost always Virgo in Vedic. Your users will be confused. Tell them upfront.

Side-by-side technical comparison

Calling the right endpoint

// Vedic (sidereal) — default
GET /api/v1/horoscope/planet-details?dob=01/10/1977&tob=11:40&lat=11&lon=77&tz=5.5&api_key=...

// Response — Sun in Virgo (sidereal position)
{ "1": { "name": "Sun", "zodiac": "Virgo", "degree": 14.8 } }

// Western (tropical)
GET /api/v1/horoscope/western-planets?dob=01/10/1977&tob=11:40&lat=11&lon=77&tz=5.5&api_key=...

// Response — Sun in Libra (tropical position, ~23° further)
{ "sun": { "zodiac": "Libra", "degree": 8.1 } }

What about Rahu and Ketu?

Rahu (North Node) and Ketu (South Node) are mathematical points — the intersection of the Moon's orbit with the ecliptic. They are not physical planets. Western astrology knows them as the Lunar Nodes but rarely uses them as prominently as Vedic astrology does.

In Vedic astrology, Rahu and Ketu are always exactly opposite (180° apart) and always retrograde. They are among the most important indicators for karma, eclipse timing, and the Rahu-Ketu dasha periods. The VedIntel API returns them as planets index 8 (Rahu) and 9 (Ketu) in the planet-details response.

Which should you use?

For Indian audience: Vedic. For Western/international: use the /horoscope/western-planetsendpoint. VedIntel supports both — include the system in your UI so users understand what they're seeing.