Eastern and Western Planets (al-kawākib al-sharqiyya wa-al-gharbiyya)
Definition
In the Dorothean visibility scheme, a planet is eastern when it lies behind the Sun at earlier zodiacal degrees and rises before him as a morning star, and western when it lies ahead of the Sun and sets after him in the evening. Each planet has its own interval from the Sun within which it counts as fit to be eastern or western: Saturn 15 degrees, Jupiter 15, Mars 18, Venus 19, Mercury 19. Inside the interval the planet is under the rays; at zero to one degree it is in the heart (cazimi).
In Tradition
In the Persian-Arabic reception of Dorotheus, eastern and western status is applied as a fitness test for the kadhkhudhāh, the house-master of life, rather than as a standalone strength. A planet must clear its own per-planet interval from the Sun, escaping the destructive nearness of the beams, before it can serve in the longevity reading. Sahl, Bonatti, and al-Bīrūnī carry the same per-planet figures, though al-Bīrūnī and Sahl give the inferiors a tighter 12-degree eastern and 15-degree western interval.
In Practice
First place each planet relative to the Sun: behind him at earlier degrees is eastern, ahead at later degrees is western. Then measure its distance from the Sun in degrees and compare it to its own interval — 15 for Saturn and Jupiter, 18 for Mars, 19 for Venus and Mercury. A planet still inside its interval is under the rays and unfit; once it clears the interval it has cleared the beams and may serve as house-master. Two conventions loosen the test: a planet is allowed seven days of motion to reach the official interval, so Saturn at 22 degrees behind the Sun already counts as western; and Jupiter and Saturn as morning risers get a special nine-day grace, letting them sit only 6 degrees from the Sun on the eastern side and still qualify, since six plus nine reaches fifteen. Use this when testing candidates for the house-master in a length-of-life reading, not as a general dignity score.
Historical Origin
The per-planet visibility intervals are set out in Dorotheus of Sidon's Carmen Astrologicum Book III, in the Persian-Arabic recension preserved through the Arabic transmission. Benjamin Dykes reconstructs them by reading Carmen alongside Sahl ibn Bishr's book on nativities, Bonatti's Liber Astronomiae, and al-Bīrūnī's Kitāb al-Tafhīm. Pingree read this chapter's distinction between superior and inferior planets as a Persian interpolation, since Hephaestio of Thebes, usually dependent on Dorotheus, does not draw it.