Platypus is a new method to calculate astrological houses. The name reflects its connection to the Placidus system, to which it is a response, as well as its genesis in Australia.

The widely used Placidus system does not reliably produce results beyond the polar circles. Even at higher sub-polar latitudes it becomes so increasingly eccentric and extreme as to be questionable. It was these sorts of objections to Placidus that led to the development of Platypus.

Platypus produces results very similar to Placidus much of the time and in many locations, but Platypus is mathematically and conceptually very different from Placidus. From equatorial to mid latitudes Platypus is not very different from Placidus. At higher sub-polar latitudes, the differences become more pronounced. Platypus does not break down at or beyond the Polar Circle.

In Platypus the MC is not the cusp of the 10th House. However, the Platypus 10th house is, as remarked above, much of the time and in many locations not very far away from the MC and in some instances even coincident with it. At higher latitudes the differences become increasingly more pronounced.

Further discussion of the 10th and other houses is witheld for now, until the full model for Platypus is published.

Key Points:

- Platypus works at all latitudes, North Pole to South Pole

- The Platypus Ascendant is the same as Placidus (and most other systems) in sub-polar latitudes.

- In Platypus the MC is not the cusp of the 10th house.

- Quadrants are of unequal size, but not the same between the two systems.

- In Platypus quadrants and intermediate houses don't shrink or expand as much as in Placidus.

- At equatorial to mid latitudes, Platypus looks quite similar to Placidus.

- At higher sub-polar latitudes the deviation of the two principal axes in Platypus is less extreme.

At the Polar Circle (≅ 67° 34'N & S):

- The Platypus Ascendant begins to behave differently to other systems.

- The Ascendant tracks through 180° of the zodiac before flipping and repeating.

- North and south track through the opposite halves of the zodiac.

Beyond the Polar Circle:

- The arc of the Ascendant's oscillation decreases the closer the location comes to the pole.

- The deviation of the two main axes from a right-angle decreases.

At the Poles (90°N & S):

- The system comes to rest. It doesn't vary at all over the day

- The Ascendant is fixed at 0° ♎︎ (N) or 0° ♈︎ (S).

- The 10th house is 0° ♋︎ (N) or 0° ♑︎ (S).

- The other houses are at 0° in the signs proceeding sequentially from those points.