Gaist astrology guide
House systems: why houses can differ between charts
Planetary zodiac positions remain the same, but house systems divide the space between the chart angles in different ways. A planet may therefore appear in a different house when the system changes.
What is calculated?
Birth time and location determine the local orientation of the sky, including the ascendant, Midheaven and house cusps. Astrology associates the twelve houses with areas of life, making an accurate time especially important for house placement.
Where houses and their meanings came from
The house idea developed in Hellenistic astrology from the daily rotation of the sky: planets rise, culminate, set and become invisible below the horizon. The four principal angles made that motion spatially legible. Places of different strength, and later twelve areas of life, grew from it. Meanings partly follow this celestial location and partly accumulated through centuries of practice. The tenth house, for example, is not linked with public role merely by a memorised list: it occupies the highest, most visible region of the circle. The fourth lies below and gathered themes of origin, ground and private foundation. This spatial logic is more useful than equating houses with signs of the same number.
Placidus
Placidus is common in modern Western astrology. It is an unequal, time-based system, so houses can vary in size. Calculations can become problematic at high geographic latitudes. Gaist uses Placidus by default when no other system was selected or when a legacy saved chart has no system recorded.
Whole Sign and equal houses
Whole Sign makes the complete rising sign the first house and each following sign another house. Equal houses instead begin at the exact ascendant and place subsequent cusps every 30 degrees. Both use equal-sized houses, but their boundaries differ.
Koch, Porphyry and other systems
Koch is another unequal, time-based system. Porphyry divides each region between the principal angles into three equal sections. Regiomontanus, Campanus, Alcabitius and topocentric houses use their own geometric or temporal constructions, producing different cusps.
What happens in polar regions?
Some time-based systems cannot be determined reliably for every moment near the polar circles. If a selected method yields no valid result there, Gaist may fall back to Porphyry for that calculation. The system actually used is shown with the result and saved charts.
Which system should I choose?
Astrology has no universally binding winner. Consistency matters most when comparing charts. Beginners can stay with the default Placidus system and later compare deliberately, focusing on changes caused by shifted house cusps.
What does not change?
Changing the house system does not alter the birth data, astronomical planetary positions or aspects between planets. It mainly changes house cusps and the assignment of planets to areas of life. The ascendant and Midheaven remain astronomical angles, although systems integrate them differently.
Astrological interpretations are intended for entertainment, inspiration and self-reflection.