Asta (combustion) occurs when a planet is too close to the Sun, making it invisible — 'set' in the Sun's light. Each planet has a threshold: Moon within 12°, Mars within 17°, Mercury within 14° (13° when retrograde), Jupiter within 11°, Venus within 10° (8° when retrograde), Saturn within 15°. A combust planet's significations are said to be 'burnt' — they operate subtly or through the affairs of the house the Sun occupies, or manifest unpredictably. The native may struggle to consciously access those planetary qualities. However, combustion is not uniformly negative — the Sun's influence can also 'purify' the planet's energy when the Sun is strong.