Me·rid·i·an
/məˈrɪdiən/
A great circle passing through the Earth's rotational poles and through the zenith (the point directly overhead) of a location on the Earth.
In astrology, the meridian serves as a fundamental reference line for chart construction and interpretation. The Local Meridian, which passes through both celestial poles and the zenith of the observer's location, intersects the ecliptic at two critical points: the Midheaven (Medium Coeli or MC) at the southern point, and the Imum Coeli (IC) at the northern point. The meridian provides a crucial astronomical reference point that many house systems utilize for chart construction, with the MC and IC often corresponding to the tenth and fourth house cusps in these systems. This celestial framework establishes the precise coordinates needed to calculate planetary positions relative to the observer's specific location and time. Understanding the meridian concept helps astrology students grasp how celestial mechanics translate into the symbolic language of the birth chart. The Midheaven point is traditionally associated with themes of career, reputation, and life direction, while the IC connects to concepts of roots, foundation, and inner security, though the specific interpretation and application of these points may vary depending on the astrological tradition and house system being used.
Source: Cindy McKean, NASA
