astro_chart

https://github.com/morriedig/astro_chart

Astrology chart calculation in pure Ruby: apparent planetary longitudes (VSOP87D, ELP-2000/82B moon, Meeus Pluto), Placidus and whole-sign houses, retrograde flags, aspects, derived points (Part of Fortune, mean Lilith), aspect-pattern detection and element statistics, plus synastry, transits, secondary progressions, composite charts and solar returns. No C extension, no external data files. Implemented from public formulas (Meeus, Astronomical Algorithms 2nd ed.).