Combustion

greek: ὑπαυγή (hupaugē); ὑπ' αὐγάς (hup' augas, 'under the rays') · arabic: احتراق (iḥtirāq, 'burning'); تحت الشعاع (taḥt al-shuʿāʿ, 'under the rays') · latin: combustio; sub radiis

Definition

Combustion (Latin combustio; Arabic iḥtirāq; Greek precursor hup' augas, 'under the rays') is the condition of a planet too close in longitude to the Sun to be visible — traditionally read as a severe debility. The standard orb is within about 8°30' of the Sun; a tighter inner band within 17' is the separate condition called cazimi, in which the planet is strengthened rather than burnt. The earlier Hellenistic 'under the beams' image describes heliacal invisibility, of which medieval combustion is a refinement.

In Tradition

Across Hellenistic, Arabic, and traditional Western practice combustion is read as the Sun overwhelming and disabling the planet's significations: 'people too close to the Sun get burnt,' as Obert paraphrases Abu Ma'shar. Masha'allah's On Reception introduces the strong-reception exception — combustion does not destroy when the Sun receives the combust planet by its domicile or exaltation. Crane treats combustion as medieval rather than native Hellenistic, descending from the older image of a 'sunken' planet under the Sun's beams.

In Practice

You check each planet's longitude distance to the Sun: within 17' is cazimi (a powerful conjunction at the Sun's heart); within 8°30' is combust (debilitated); between roughly 8°30' and 17° is under-the-beams (weakened but recoverable); outside that range is free of solar interference. In horary judgment a combust significator is read as compromised — the matter is overwhelmed, hidden, or the querent's significator burnt. Strong-reception exceptions (Masha'allah) mute the destruction: a combust Mercury in Virgo (its own sign) escapes the worst, since the Sun receives it by domicile. Dorotheus's Book I Ch 14 uses the combust state to trigger substitute-Lot formulas, signaling that the combust planet cannot carry its standard significator role.

Historical Origin

The 'under the rays' image is Hellenistic (Greek hup' augas), referring originally to heliacal invisibility. The 8°-arc combustion convention is a medieval Arabic-Latin refinement — Crane traces its origin to the depiction of a planet sunken within the Sun's beams. Masha'allah's On Reception Ch 3 codifies the strong-reception exception; Dorotheus's Carmen I.14 §5 uses the combust state as a trigger for substitute calculations; Lilly transmits the full doctrine into early modern English horary in Christian Astrology Book 1.

Etymology

Origin: Latin. Meaning: From combustio ('a burning up'), the medieval Latin translation of Arabic iḥtirāq ('burning'), itself rendering Greek hupaugē..

Further Reading