Decanates (decans)

A decanate (decan, duad) is a ten-degree subdivision of each zodiac-signs, giving three decans per sign (0°–10°, 10°–20°, 20°–30°). Western traditions assign sub-rulers or symbolic images to each decan for finer grain than the sign alone.

Hellenistic and medieval sources used decan “faces”; modern astrologers may map decans to Chaldean order or elemental sub-structure. Software can report which decan a planets occupies from its absolute longitude.

Decanates do not replace sign and house interpretation; they nuance it—especially when several planets share a sign but occupy different decans. Works with dignities in traditional study. Same longitudes as ecliptic-longitude.