decan

astronomy

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June 25, 2026

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The term "decan" has two primary meanings: in astronomy and in astrology.

In astronomy, decans are 36 star configurations that circle the sky. They were used by the ancient Egyptians to divide the night into 24 hours and are depicted in ancient Egyptian tomb ceilings and star maps.1

In astrology, a decan refers to one of the three 10-degree divisions within each of the 12 signs of the zodiac. Each decan is also associated with a specific ruler. This division of the zodiac into smaller segments was utilized in Hellenistic astrology for more detailed interpretations in birth charts.23

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astronomical map
The decans
Two other astronomical reference systems developed independently in early antiquity, the lunar mansions and the Egyptian decans. The decans are 36 star configurations circling the sky somewhat to the south of the ecliptic. They make their appearance in drawings and texts inside coffin lids…
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Two other astronomical reference systems developed independently in early antiquity, the lunar mansions and the Egyptian decans. The decans are 36 star configurations circling the sky somewhat to the south of the ecliptic. They make their appearance in drawings and texts inside coffin lids…
Read More

astrology
Astrology in the Hellenistic period (3rd century bce to 3rd century ce)
…subdivided each into various parts—decans of 10° each, fines (“bounds”) of varying lengths, and dōdecatēmoria of 2°30′ each—each of which is also dominated by a planet. Scattered at various points throughout the ecliptic are the planets’ degrees of exaltation (high influence), opposite to which are their degrees of dejection…
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…subdivided each into various parts—decans of 10° each, fines (“bounds”) of varying lengths, and dōdecatēmoria of 2°30′ each—each of which is also dominated by a planet. Scattered at various points throughout the ecliptic are the planets’ degrees of exaltation (high influence), opposite to which are their degrees of dejection…
Read More