Arc of Vision

Definition

The Arc of Vision, traditionally called the arcus visionis, is the angular measure used to judge when a planet or star becomes visible after sunset or before sunrise. It reflects how far the Sun must be below the horizon for the body to appear. Required values vary with the body’s brightness, location, season, latitude, and atmospheric conditions.

Astrological Meaning

Classical astrologers use the Arc of Vision when evaluating heliacal rising and setting—the first or last observable appearance of a celestial body near the Sun. A planet emerging into visibility may be interpreted as becoming more apparent, expressive, or available for action, while one disappearing into the Sun’s light may suggest withdrawal or reduced outward prominence. These judgments belong to a wider traditional framework that also includes combustion, cazimi, and being under the Sun’s beams. The Arc of Vision is not simply the planet’s zodiacal distance from the Sun; it is a visibility criterion connected to the horizon and local sky.

Why It Matters

This concept helps refine traditional chart analysis by distinguishing an actually visible planet from one obscured by sunlight. It can add context to natal charts, event charts, and mundane work, especially when heliacal phenomena are emphasized. Because historical tables and modern astronomical calculations may use different thresholds, astrologers should state their method and avoid treating visibility as a single fixed boundary.

Related Encyclopedia Entries

• Traditional Astrology
• Heliacal Rising
• Combustion
• Under the Sun's Beams
• Cazimi
• Natal Chart