Natal Twelfth-Parts Admission

Verdict: admit. 6.3.0 placement: new atom + REST; optional profile overlay later.

Object

The Hellenistic dodekatemorion of an ecliptic longitude. Each 30° sign is cut into twelve equal 2°30′ slices. The ordinary natal projection is:

projected = (sign_start + 12 × degree_in_sign) mod 360

Seams are left-closed, right-open: [0, 2.5), [2.5, 5), …, [27.5, 30).

Sources

• Ptolemy, Tetrabiblos I.22
• Vettius Valens, Anthologies (Riley), multiple uses of twelfth-parts
• Dorotheus, Carmen I.8
• Firmicus Maternus, Mathesis II.17
• Skyscript / Wikipedia statement of the 12× formula (Capricorn 17° → Cancer 24°)

Not this object

• Vedic Dwadashamsa / D12 starting-sign variants
• Abu Ma'shar Nine Parts
• Sahl/Dorotheus electional “malefic in the Moon’s twelfth-part sign”
• Chaldean faces (10°) and triplicity decans

Fail-closed

Non-finite longitude raises. Degree 30.0 of a sign does not occur after normalization (longitude % 360, then // 30).