Foundations of Astrology: Regiomontanus

The Regiomontanus house system is a quadrant-based method of chart division developed in the 15th century by German mathematician and astrologer Johannes Müller, known as Regiomontanus. Like other quadrant systems, it begins with the Ascendant and Midheaven to anchor the structure of the chart, then divides the celestial equator (rather than the ecliptic) into twelve equal segments. The house cusps are projected from the Earth's equator onto the zodiac, resulting in unequal house sizes that vary with geographic latitude and time of birth. Historically, Regiomontanus gained popularity during the Renaissance and was favored by astrologers such as William Lilly, especially in the practice of horary astrology—a form of astrology focused on answering specific questions. Its mathematically rigorous structure was considered well-suited to the scholarly spirit of the era and remains respected for its clarity in timing and event-focused interpretation. What makes Regiomontanus relevant today is its connection to traditional methods of chart analysis and its value in timing-based work. Symbolically, it reflects a worldview that prioritizes motion, perspective, and precision—offering insight into how celestial dynamics interact with human circumstances. For those drawn to the classical roots of astrology, Regiomontanus stands as a bridge between ancient technique and Renaissance refinement, reminding us that the architecture of the chart is always a mirror of both space and time.