Not an aspect with an orb of its own: the twelfth-part is a derived degree, and it is then read by the ordinary aspects and orbs. A partile contact between a derived degree and a planet is the only one traditionally judged.
A technique for deriving a second position from a first. Each sign is divided into twelve parts of 2 degrees 30 minutes, and each part is assigned to a sign in order from the sign itself: the first twelfth of Aries is Aries, the second is Taurus, and so on. So 2°30' of Aries has its twelfth-part in Taurus, and 10° of Aries in the fifth twelfth, Leo. The derived degree is then read like any other degree, and the tradition used it to find the hidden sign of a planet and to amplify a judgement already made from the natal position.
Magical Uses
AmplificationHidden signFine timingDeepening a judgement