Porphyrius Topocentric Birth Chart Calculator

This calculator uses Porphyrius house system and topocentric coordinate system.

The Porphyrius house system, named after the 3rd-century philosopher Porphyry, is a quadrant system that divides the space between the angles (Ascendant, IC, Descendant, MC) into three equal parts. It is one of the oldest house systems still in use today.

The topocentric system calculates planetary positions relative to the observer's location on Earth's surface, rather than from Earth's center (geocentric). This results in slightly different positions, particularly for the Moon, and is preferred by some astrologers for its physical accuracy.

For more features including saving charts, transit charts, synastry charts, and more settings please use True Sky online astrology software.