A planet is combust when it sits within a few degrees of the Sun, close enough that its independent expression gets overwhelmed by solar light. Hellenistic astrology calls this loss of testimony; Vedic astrology calls it Astangata, body hidden. The orb varies by planet, from 8° for retrograde Venus to 17° for Mars.

The doctrine is older than either tradition's modern form. Sahl ibn Bishr writes about combustion in the ninth century with a roughly uniform 15° orb. William Lilly carries a similar generic orb (~8°30′) into Christian Astrology(1647). The differentiated per-planet table this calculator uses (Mars 17°, Saturn 15°, Mercury 14°, and so on) is Vedic, codified in Mantreswara's Phaladeepika and the Brihat Parashara Hora Shastra. Some modern Western traditional astrologers adopt the Vedic table because it differentiates the planets, with Mercury and Venus tightening further when retrograde.

What it means in practice: a combust Mercury still rules the houses it rules, still sits in its sign, still makes its aspects. But you'd treat its testimony with caution. The planet's significations show up muffled, like a voice trying to speak over a much louder one.

Combustion is the angular distance between the planet and the Sun along the ecliptic. We compare that distance to a per-planet threshold and flag the planet if it falls inside.

The retrograde columns matter for Mercury and Venus only, because those are the only classical planets that go retrograde near the Sun. The Vedic tables give Mercury and Venus narrower thresholds when retrograde. That is a threshold rule, not an automatic verdict that retrograde combustion is worse in every chart. Some Jyotish explanations treat retrograde motion as added resisting strength, while the Western reading still weighs whether the planet is applying to or separating from the Sun. Lilly notes that retrograde Mercury near the Sun behaves differently but doesn't differentiate the orb numerically.

The Moon row is the ambiguous one. In Vedic astrology, the Moon within 12° of the Sun is combust, which is the dark side of the lunar month, the days around the New Moon. Hellenistic sources are split. Some authors don't classify the Moon as combustible at all, on the grounds that every month would otherwise contain a week of debilitation. We flag the Moon so you can see it. Whether to read it as a hard debility depends on your tradition.

A planet near the Sun isn't in one state. It's in one of four:

1. Cazimi, within 17 arcminutes (about 0.28°) of the Sun's center. The planet is in the Sun's heart; classical sources flip the verdict from weak to fortified. Rare and brief.
2. Heart of the Sun, within roughly 1° of exact conjunction but outside cazimi. A neutral zone in some authors, an extended cazimi in others.
3. Combust, the per-planet orb shown above. The classical “loss of testimony” range.
4. Under the beams, from the combustion threshold out to about 17°. The planet is no longer fully concealed but isn't yet operating at full strength.

If you want the cazimi side, that's a separate tool: the cazimi calculator handles the 17-arcminute threshold and the 1° heart-of-Sun band, with dates per planet through 2026. This page is the combust side, the wider bands where most of the practical interpretation happens.

Combustion isn't a single verdict. It's a condition that interacts with the rest of the chart. Four questions sharpen the reading.

Planetary positions come from the JPL DE440s planetary ephemeris via ANISE. Geocentric, true-of-date positions are compared by angular separation, the same geometry the cazimi calculator uses, with different threshold lookups for the orb table.

Classical sources cited above:

• Sahl ibn Bishr, Introductio in Astrologiam (early 9th century)
• William Lilly, Christian Astrology (1647), book 1, on essential and accidental fortitudes
• Mantreswara, Phaladeepika, on planetary states
• Maharishi Parashara, Brihat Parashara Hora Shastra, sections on graha bala

Modern practitioners synthesizing both lineages: Chris Brennan, Hellenistic Astrology: The Study of Fate and Fortune (2017) for the Western tradition, with Komilla Sutton and B.V. Raman for the Vedic.

For a reading framework that combines combustion with sect, dignity, and the topics of the houses, see the essential dignity calculator and the Hellenistic chart hub.

In Vedic astrology, combustion is called Astangata, literally “body hidden.” The differentiated per-planet table this calculator uses is functionally Vedic in origin. Hellenistic sources never formalized the same granular table; they tended to use a single broader orb (Sahl ~15°, Lilly ~8°30′). When modern Western practitioners want a per-planet figure, they often borrow the Vedic numbers, which is what this tool does.

Vedic readings commonly judge mitigation through the planet's dignity, house rulership, benefic or malefic support, and the Sun itself. Western sources arrive at similar nuance through dignity, sect, reception, and whether the planet is emerging from or moving deeper into the beams.

One technical note for sidereal practitioners: combustion is a Sun-planet angular separation, which is invariant under the tropical/sidereal ayanamsa shift. The Sun-Mars angle is the same in both zodiacs, so this calculator's results apply identically to a sidereal chart. If you want Lahiri sidereal positions for sign placements and dignity work, the sidereal chart calculator handles that side of the chart.