House systems
There are several ways to divide the sky into houses. We use Placidus.
Every house system agrees on the Ascendant, but they disagree on how to divide the space between the four angles. Whole Sign gives each house one entire sign; Equal makes every house exactly 30°; Placidus and Koch divide by time, following how long each degree takes to rise.
Lunastra uses Placidus, the most widely used system in modern Western astrology. It has one weakness: near the poles some degrees never rise, so it cannot be calculated. For births above roughly 66° latitude we switch to Porphyry, which divides each quadrant evenly, and we tell you when we do.
If a planet sits close to a house cusp, another system may place it in the neighbouring house. That is normal, and a reason to read a placement near a cusp as touching both areas of life.