Developer Breaks Down Aspect and Orb Calculations in Open-Source Python Astrology Engine

A developer has shared how they model astrological aspects and orbs in a Python-based astrology engine called GetBirthChart, available on GitHub. At its core, the system calculates how closely two planetary positions on a 360-degree circle approach a target angle, using a normalization function to handle wrap-around cases such as the short arc between 358° and 2°. Orbs — the tolerance thresholds that allow near-exact angles to still qualify as aspects — are computed as the absolute difference between the actual separation and the target angle. The engine covers major aspects including conjunction, sextile, square, trine, and opposition, keeping calculation logic strictly geometric and separate from any interpretive meaning. The developer emphasizes unit-testing individual functions over visual checks, describing the goal as making the calculation layer predictable and free of domain interpretation.