Placidus
Starmora defaults to Placidus. It divides time intervals of ecliptic points in daily celestial motion. The ascendant is the 1st cusp and MC the 10th, and houses can have unequal widths. It is undefined at or beyond the polar circles; choose Whole Sign or Equal houses there.
Porphyry
Each of the four ecliptic quadrants between the ascendant, descendant, MC and IC is divided into three equal parts. The quadrants can have different widths, so all houses need not be equal. Where a polar horizon prevents ordered quadrant houses, choose Whole Sign or Equal. The detailed Porphyry guide covers history, quadrant construction and dated cusp tables.
Whole Sign
The complete sign containing the ascendant becomes the 1st house, and each following sign becomes the next house. Every house spans 30° and starts at 0° of its sign. The ascendant's actual degree is retained separately in the chart.
Equal houses
In Equal houses, the 1st house begins at the ascendant's exact degree and each next house begins 30° later. If the ascendant is at 18° of its sign, successive house cusps are at 18° of the following signs. Sign boundaries and house boundaries do not have to coincide.
Use the same method when comparing
Changing the house system leaves planetary signs and degrees unchanged but can change house numbers. Match the zodiac, time, coordinates and house system when comparing calculations. Starmora defaults to Placidus and also offers Whole Sign, Equal and Porphyry. House construction is a method preference separate from planetary-longitude accuracy. The four guides below cover history, formulas, MC, limitations and comparisons using the same dated example.
Sources and approach
These sources explain the page's traditional concepts or calculation context. Original Starmora examples and reflection prompts are not predictions attributed to the sources.