House Systems

The sky is round, and there is no single obvious way to cut it into twelve houses. Over the centuries astronomers and astrologers have proposed several methods, called house systems. They give different answers to the same question: where does each house begin? Natalora lets you choose from seven in the chart options.

The seven systems

• Placidus: the default. Based on how much time the sky takes to turn, so houses can be unequal in size. It is the most common choice in modern Western astrology.
• Koch: also time-based and similar to Placidus, but built from the birthplace in a slightly different way.
• Equal: starts at the Ascendant and makes every house exactly 30 degrees.
• Whole Sign: the sign of the Ascendant becomes the whole first house, the next sign the second, and so on. It is simple and very old.
• Porphyry: divides the space between each pair of angles into three equal parts.
• Regiomontanus: slices the sky using the celestial equator. It is popular in medieval-style work.
• Campanus: slices the sky using the vertical circle running through the east and west points.

What changes

The house cusps move, and so does the house number of a planet that sits near a boundary. A planet can be in the 10th house in one system and the 9th in another. House sizes also differ: in some systems they are all equal, in others they stretch and shrink.

What does not change

Your planets stay in exactly the same signs and degrees. The Ascendant and the Midheaven (MC) also stay the same. The aspects between planets do not move either.

Very high latitudes

Near the polar circles, about 66 degrees north or south, time-based systems such as Placidus and Koch stop working properly, because some degrees of the zodiac never rise or set. For such places, Natalora falls back to Porphyry houses, which still work there, and the chart page tells you when this has happened. In a few polar cases Regiomontanus and Campanus fall back as well.

Which should you pick?

If you are new, keep Placidus. If you follow a specific tradition, choose that one. If a planet seems to be on the wrong side of a house line, try another system and see whether the story holds up.