A planet close to the Sun is lost in its glare. It is called combust, or asta. Each planet has its own limit. Moon 12°, Mars 17°, Mercury 14°, Jupiter 11°, Venus 10°, Saturn 15°. A retrograde Mercury is combust within 12°, a retrograde Venus within 8°. One translator gives Saturn 16°. Rahu and Ketu are never combust.
☕ A star you cannot see at dawn
Planets move round the sky at different speeds. Now and then a planet comes close to the Sun. Then it rises and sets with the Sun, and you cannot see it. The old astronomers called this asta, setting. In English it is called combustion.
Parashara's verses grade a planet by its distance from the Sun (Brihat Parashara Hora Shastra (Santhanam–Kapoor ed.), ch. 7, vv. 28–29, pp. 99–100). Opposite the Sun it is fully effective. At the Sun's own degree it is weakest. In between, it is graded in proportion.
Combustion turns this into a yes-or-no rule. Each planet has an orb, a distance from the Sun. Inside it, the planet is combust. Two translators give orbs: one in his note to Jataka Parijata (tr. Subramanya Sastri), ch. V, v. 7, p. 237, the other in a table in Brihat Parashara Hora Shastra (Santhanam–Kapoor ed.), ch. 7, p. 100.
The two agree on the Moon, Mars, Mercury, Jupiter and Venus, and on the smaller limits for a retrograde Mercury and Venus. They differ on Saturn: 15° in the first, 16° in the second. The second also gives a retrograde Mars 8°; the first gives Mars one figure. Both are translators' notes, not verses. So neither outranks the other.
Rahu and Ketu are never combust. They are points, not bodies with light. The note to Parashara's verses says so.
At a glance
- Moon: within 12°
- Mars: within 17°
- Mercury: within 14°
- Jupiter: within 11°
- Venus: within 10°
- Saturn: within 15°
- Retrograde Mercury: within 12°
- Retrograde Venus: within 8°
- Retrograde Mars, Jupiter and Saturn: the same orb as in direct motion
- Sun, Rahu and Ketu: never combust in Nava's chart.
- Saturn: 16° in the translator's table in Brihat Parashara Hora Shastra (Santhanam–Kapoor ed.), ch. 7, p. 100; 15° in the translator's note in Jataka Parijata (tr. Subramanya Sastri), ch. V, v. 7, p. 237.
- Retrograde Mars: 8°, in Parashara's translator's table only (ch. 7, p. 100).
- What Nava follows: Saturn 15° in both motions, and retrograde Mars 17° as in direct motion; these are our choice where the two translators split. Where both agree, Nava follows them: the Moon 12°, retrograde Mercury 12° and retrograde Venus 8°.
Frequently asked questions
What does combust mean in a birth chart?
A planet is combust when it is within its orb of the Sun, measured in degrees of longitude. It is a definition of nearness to the Sun. Combust means: Moon within 12°, Mars within 17°, Mercury within 14°, Jupiter within 11°, Venus within 10°, Saturn within 15°; a retrograde Mercury within 12°, a retrograde Venus within 8°.
Is Saturn's orb 15° or 16°?
The two translators differ. Jataka Parijata's translator gives 15°. Parashara's translator gives 16° in his table. Both are notes, not verses. What Nava follows: 15°, in direct and retrograde motion alike.
Does a retrograde planet have a smaller orb?
For Mercury and Venus, yes. Both notes give retrograde Mercury 12° and retrograde Venus 8°. Nava uses 12° for a retrograde Mercury and 8° for a retrograde Venus. So in Nava's chart a retrograde Venus 9° from the Sun is not combust, though a direct Venus there is. Parashara's translator also gives retrograde Mars 8°. The other note gives Mars one figure. What Nava follows: Mars 17° in both motions, our choice where the two split.
Can the Moon, Rahu or Ketu be combust?
The Moon can. Both notes give it a 12° limit. Nava uses 12° for the Moon. Parashara's translator says Rahu and Ketu are never combust; the Jataka Parijata note gives them no figure. They are points, not lit bodies.
Deep dive: measuring the distance
How the distance is taken. A worked example.
☀️ How the distance is taken
Take the planet's longitude and the Sun's longitude, both sidereal. Find the gap between them, the short way round the circle. If the gap is at most the planet's orb, the planet is combust.
Signs do not matter here. A planet in the next sign can still be combust, and a planet in the Sun's own sign need not be.
🔢 A worked example
The Sun is at 20° of Simha (Leo). Mercury is at 2° of Kanya (Virgo). The gap is 12°. Mercury's orb is 14°, so Mercury is combust.
Venus at 3° of Kanya (Virgo) is 13° away. Venus's orb is 10°, so Venus is not combust.
Read the planets' natures first in the grahas, and their best and worst signs in exaltation and debilitation.