Astrology & myths · Hellenistic mundane astrology · Ptolemy, Tetrabiblos II.4–6
Eclipses as omens in Ptolemy
Ptolemy's second book is about whole peoples and places rather than individuals, and it begins with eclipses.
The method
Ptolemy calls the conjunctions of the sun and moon at eclipse the first and most potent cause of general events. He reads which regions are affected from where the eclipse falls, and how long its effect lasts from its length: as many years as the eclipse lasts in hours, for the Sun.
The sky's side
Eclipses themselves are geometry, predictable centuries ahead; this site lists them, with maps, on its eclipse pages. Looking at a partial eclipse needs proper eye protection (NASA).
Astrology and myth are presented here as symbolic and historical traditions, not as predictions. The sky's positions and times on this site are calculated the same way in every lens.
Sources
- LacusCurtius (Bill Thayer) Ptolemy, Tetrabiblos, Book II, ch. 4–6 (trans. F. E. Robbins) (opens in a new tab) for eclipses as the first cause of general events; a solar eclipse's hours read as years · checked 2 October 2026
- NASA Eclipse Viewing Safety (opens in a new tab) for ISO 12312-2 viewers; sunglasses unsafe; no optics without front filters; pinhole projection; totality only · checked 2 October 2026