About

• The planetary and cuspal positions are calculated using the Swiss Ephemeris developed by Dieter Koch and Dr. Alois Treindl at Astrodienst. The Swiss Epemeris reproduces planetary positions from NASA JPL Horizons and is considered a gold standard for accurate astrological data. Sidereal zodiac and Placidus house systems are used.
• Planetary orbs (of 3°20' and 6°40' for Sun) are applied to determine houses by default (when orb does not cross into a new sign). This can be disabled in the settings.
• Latitude and Longitude for places come from Google Maps and timezones are automatically adjusted for any daylight savings time.
• KP-Ephemeris Ayanamsa, KP-Senthilathiban Ayanamsa and Lahiri (IAE 1985) Ayanamsa are supported as built into the Swiss Ephemeris library. The default ayanamsa is KP-Ephemeris.
• There is often much debate around which KP ayanamsa to use. Based on my research, the KP-Senthilathiban Ayanamsa provides the most astronomically accurate data, but the practical differences in planetary positions and house cusps between KP-Ephemeris and KP-Senthilathiban are less than 1 arc-minute. To contextualize this: if the time of the chart changes by just 4 seconds, or if the location changes by only ~2 km, the lagna moves by 1 arc-minute. Astrological interpretation is as much of an art made possible by the divine, as it is a science of the stars and I personally think small differences in ayanamsa between KP-Ephemeris and KP-Senthilathiban can be overlooked. For the curious astrologer, I recommend reading the following resources:
  • Swiss Ephemeris docs on KP Ayanamsa, Precession Rates and Lahiri Ayanamsa
  • Nachiappan Narayanan's blog on Krishnamurti Paddhati, KP Ayanamsa and Resources
  • V.Subramanian's Analysis of KP Ayanamsa based on Senthilathiban's work.
• Fortuna is calculated as (Ascendant + Moon - Sun). Some western astrological traditions have different calculations for day vs. night, but the simplified calculation is common in vedic and KP astrology.