Whenever a planet appears very near to the Sun, it is divested of its brightness (luster) and is called a combust planet. While in the state of combustion, the planets lack power to protect and promote the significations/houses ruled by them. The planets are considered combust when they have following longitudinal difference with the Sun on either side:
- Moon – 12 degrees
- Mars – 17 degrees
- Mercury – 14 degrees (12 degrees when retrograde)
- Venus – 10 degrees (8 degrees when retrograde)
- Jupiter – 11 degrees
- Saturn – 15 degrees
The effects of combustion are maximum when the planet is within 5 degrees on either side of the Sun.
A planet is combust when it is in conjunction with the Sun and therefore hidden from sight by the light of the Sun. Traditionally this is a serious debility and implies that the planet is weakened or restricted in power. However, if the planet is within 17 minutes of the Sun, it is termed Cazimi – in the heart of the Sun – and considered strengthened by the union.
In his Introduction, William Lilly stated that the combust planet should be in the same sign as the Sun and within 8° 30′ – beyond this distance, but within 17 ° of the Sun, the planet is said to be under the Sun’s beams. This condition is debilitating, but not as severe as combustion.