Decans
Encyclopedia
The Decans are 36 groups of stars (small constellations) which rise consecutively on the horizon throughout each earth rotation. The rising of each decan marked the beginning of a new decanal "hour" (Greek hōra) of the night for the ancient Egypt
Ancient Egypt
Ancient Egypt was an ancient civilization of Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh...

ians, and they were used as a sidereal star clock
Star clock
A star clock is a method of using the stars to determine the time. This is accomplished by measure the Big Dipper's position in the sky based on a standard clock, and then employing simple addition and subtraction. This method requires no tools; others use an astrolabe and a planisphere.A clock's...

 beginning by at least the 9th or 10th Dynasty (ca 2100 BCE.)

Because a new decan also appears heliacally
Heliacal rising
The heliacal rising of a star occurs when it first becomes visible above the eastern horizon for a brief moment just before sunrise, after a period of time when it had not been visible....

 every ten days (that is, every ten days, a new decanic star group reappears in the eastern sky at dawn right before the Sun rises, after a period of being obscured by the Sun's light), the ancient Greeks called them dekanoi (pl. of dekanos) or "tenths" (and when the concept of decans reached northern India, they were called drekkana in Sanskrit
Sanskrit
Sanskrit , is a historical Indo-Aryan language and the primary liturgical language of Hinduism, Jainism and Buddhism.Buddhism: besides Pali, see Buddhist Hybrid Sanskrit Today, it is listed as one of the 22 scheduled languages of India and is an official language of the state of Uttarakhand...

.) These predictable heliacal re-appearances by the decans were eventually used by the Egyptians to mark the divisions of their annual solar calendar
Calendar
A calendar is a system of organizing days for social, religious, commercial, or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. The name given to each day is known as a date. Periods in a calendar are usually, though not...

. Thus the heliacal rising of Sirius
Sirius
Sirius is the brightest star in the night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek: Seirios . The star has the Bayer designation Alpha Canis Majoris...

 marked the annual flooding of the Nile.

Eventually this system led to a system of 12 daytime hours and 12 nighttime hours, varying in length according to the season. Later, a system of 24 "equinoctial" hours was used.

After astrology
Hellenistic astrology
Hellenistic astrology is a tradition of horoscopic astrology that was developed and practiced in Hellenistic Egypt and the Mediterranean, whose texts were written in Greek , mainly around the late 2nd or early 1st century B.C.E...

 was introduced to Egypt, various systems attributing astrological significance to decans arose. Decans were connected, for example, with various diseases and with the timing for the engraving of talismans for curing them; with decanic "faces" (or "phases"), a system where three decans are assigned to each zodiacal sign, each covering 10° of the zodiac, and each ruled by a planetary ruler (see below); and correlated with astrological signs.

Decans continued to be used throughout the Renaissance
Renaissance
The Renaissance was a cultural movement that spanned roughly the 14th to the 17th century, beginning in Italy in the Late Middle Ages and later spreading to the rest of Europe. The term is also used more loosely to refer to the historical era, but since the changes of the Renaissance were not...

 in astrology and in magic, but modern astrologers almost entirely ignore them.

Ancient Egyptian origins

Decans first appeared in the 10th Dynasty (2100 BCE) on coffin lids. The sequence of these star patterns began with Sothis/Sirius, and each decan contained a set of stars and corresponding divinities. As measures of time, the rising and setting of decans marked 'hours' and groups of 10 days which comprised an Egyptian year.

There were 36 decans (36 X 10 = 360 days). plus 5 added days to compose the 365 days of a solar based year. Decans measure sidereal time and the solar year is 6 hours longer; the Sothic and solar years in the Egyptian calendar realign every 1460 years. Decans represented on coffins from later dynasties (such as King Seti I) compared with earlier decan images demonstrate the Sothic-solar shift.

Table of Faces (or Decanates)

"The Faces of the Planets" * (Lilly)
Sign First Decan ruler
(0 - 9.999 deg.)
Second Decan ruler
(10 - 19.999 deg.)
Third Decan ruler
(20 - 29.999 deg.)
Aries
Aries (astrology)
Aries is the first astrological sign in the Zodiac, which spans the zodiac between the zero degree and the 29th degree of celestial longitude. The Sun enters Aries when it reaches the northern vernal equinox, which is usually on March 21 each year, and remains in this sign until around April 20...

Mars Sun
Sun (astrology)
The sun is considered a very important part of astrology. It, as well as the Moon, are the most important of the astrological planets, and the two of them are often referred to as the luminaries. In Greek mythology the sun was represented by Apollo, the god of light, and Helios, the god of the sun...

Venus
Taurus
Taurus (astrology)
Taurus is the second astrological sign in the Zodiac, which spans the zodiac between the 30th and 59th degree of celestial longitude. Generally, the Sun transits this area of the zodiac between April 21 to May 21 each year...

Mercury Moon
Moon (astrology)
The Moon is the Earth's companion satellite. The Moon is large enough for its gravity to affect the Earth, stabilising its orbit and producing the regular ebb and flow of the tides. The Moon is also familiar to us for its different phases, waxing and waning in appearance in an unchanging cycle...

Saturn
Gemini
Gemini (astrology)
Gemini is the third astrological sign in the Zodiac, which spans the Zodiac between the 60th and 89th degree of celestial longitude. Generally, the Sun transits this area of the zodiac between May 21 to June 20 each year...

Jupiter Mars Sun
Sun (astrology)
The sun is considered a very important part of astrology. It, as well as the Moon, are the most important of the astrological planets, and the two of them are often referred to as the luminaries. In Greek mythology the sun was represented by Apollo, the god of light, and Helios, the god of the sun...

Cancer
Cancer (astrology)
Cancer is the fourth astrological sign in the Zodiac. It is considered a water sign and one of four cardinal signs. Cancer is ruled by the Moon. Individuals born when the Sun is in this sign are considered Cancerian individuals...

Venus Mercury Moon
Moon (astrology)
The Moon is the Earth's companion satellite. The Moon is large enough for its gravity to affect the Earth, stabilising its orbit and producing the regular ebb and flow of the tides. The Moon is also familiar to us for its different phases, waxing and waning in appearance in an unchanging cycle...

Leo
Leo (astrology)
Leo is the fifth astrological sign of the Zodiac, originating from the constellation of Leo. In astrology, Leo is considered to be a "masculine", positive sign. It is also considered a fire sign and is one of four fixed signs ruled by the Sun.Individuals born when the Sun is in this sign are...

Saturn Jupiter Mars
Virgo
Virgo (astrology)
Virgo is the sixth astrological sign in the Zodiac, which spans the zodiac between the 150th and 179th degree of celestial longitude. Generally, the Sun transits this area of the zodiac between August 23 to September 22 each year...

Sun
Sun (astrology)
The sun is considered a very important part of astrology. It, as well as the Moon, are the most important of the astrological planets, and the two of them are often referred to as the luminaries. In Greek mythology the sun was represented by Apollo, the god of light, and Helios, the god of the sun...

Venus Mercury
Libra
Libra (astrology)
Libra is the seventh astrological sign in the Zodiac, originating from the constellation of Libra. In astrology, Libra is considered a "masculine", positive sign. It is also considered an air sign and is one of four cardinal signs...

Moon
Moon (astrology)
The Moon is the Earth's companion satellite. The Moon is large enough for its gravity to affect the Earth, stabilising its orbit and producing the regular ebb and flow of the tides. The Moon is also familiar to us for its different phases, waxing and waning in appearance in an unchanging cycle...

Saturn Jupiter
Scorpio
Scorpio (astrology)
|Infobox align="right" style="border:3px solid white;"||style="text-align: center;"|Scorpio is the eighth astrological sign in the Zodiac, which spans the zodiac between the 210th and 239th degree of celestial longitude. Generally, the Sun transits this area of the zodiac between 24 October and...

Mars Sun
Sun (astrology)
The sun is considered a very important part of astrology. It, as well as the Moon, are the most important of the astrological planets, and the two of them are often referred to as the luminaries. In Greek mythology the sun was represented by Apollo, the god of light, and Helios, the god of the sun...

Venus
Sagittarius
Sagittarius (astrology)
Sagittarius is the ninth astrological sign in the Zodiac, which spans the zodiac between the 240th and 269th degree of celestial longitude...

Mercury Moon
Moon (astrology)
The Moon is the Earth's companion satellite. The Moon is large enough for its gravity to affect the Earth, stabilising its orbit and producing the regular ebb and flow of the tides. The Moon is also familiar to us for its different phases, waxing and waning in appearance in an unchanging cycle...

Saturn
Capricorn Jupiter Mars Sun
Sun (astrology)
The sun is considered a very important part of astrology. It, as well as the Moon, are the most important of the astrological planets, and the two of them are often referred to as the luminaries. In Greek mythology the sun was represented by Apollo, the god of light, and Helios, the god of the sun...

Aquarius Venus Mercury Moon
Moon (astrology)
The Moon is the Earth's companion satellite. The Moon is large enough for its gravity to affect the Earth, stabilising its orbit and producing the regular ebb and flow of the tides. The Moon is also familiar to us for its different phases, waxing and waning in appearance in an unchanging cycle...

Pisces Saturn Jupiter Mars
  • as used as an essential dignity
    Essential dignity
    In astrology, essential dignity is the strength of a planet or point's zodiac position, judged only by its position by sign and degree, or its essence--what the pre-eminent 17th-century astrologer William Lilly called "the strength, fortitude or debility of the Planets [or] significators." In other...

     in astrology.


Notice that rulerships follow a repeating pattern, the so-called "Chaldaean" order of the planets: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon.
This planetary order, in which the Sun stands at the center of the continuum, with the planets between the Sun and the Earth on one side and the outer planets on the other side, reflected the perception of the speed of each planet's motion as seen from the Earth.

Decans or "faces" are the least important of the essential dignities
Essential dignity
In astrology, essential dignity is the strength of a planet or point's zodiac position, judged only by its position by sign and degree, or its essence--what the pre-eminent 17th-century astrologer William Lilly called "the strength, fortitude or debility of the Planets [or] significators." In other...

, representing about one-fifteenth of a planet's overall strength in medieval astrology.

Ancient India

In India, the division of the zodiac into 36 ten degree portions is called either the drekkana (drekkāṇa),the dreshkana (dreṣkāṇa), or the drikana (dṛkāṇa).

The iconography and use of the drekkana’s is mention earliest by Sphujidhvaja in Yavanajataka
Yavanajataka
The Yavanajātaka of Sphujidhvaja is an ancient text in Indian astrology....

 (269-70 CE), and given detailed treatment by Varahamihira
Varahamihira
Varāhamihira , also called Varaha or Mihira, was an Indian astronomer, mathematician, and astrologer who lived in Ujjain...

 in his Brihat-Samhita (550 CE). Modern scholars believe the decans were imported into India through the Greeks, who learned about them from the Egyptians.

There are multiple types of drekkana in use in Indian astrology. The parivritti drekkana goes in order of the signs; the first decan is Aries, the second is Taurus, the third is Gemini, the fourth is Cancer, etc. Then there is the trinal calculation which utilizes the elemental trines to each sign; In Aries there is Aries, Leo, and Sagittarius, while in Taurus there is Taurus, Virgo, and Capricorn. There are in total four variations of drekkana calculations. Indian astrologers will calculate these signs (varga
Varga (astrology)
The term varga in Indian astrology refers to the division of a zodiacal sign into parts...

) and create a new chart based upon the sign placement for predictive purposes.

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