Decan

Decans first appeared in the First Intermediate Period of Egypt on coffin lids. The sequence of these star patterns began with Sirius ("Sothis"), 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 ten days, which comprised an Egyptian year. The Book of Nut covers the subject of the decans.

There were 36 decans (36 × 10 = 360 days), plus five added days to compose the 365 days of a solar-based year. Decans measure sidereal time and the solar year is six hours longer; the Sothic and solar years in the Egyptian calendar realign every 1460 years. Decans represented on coffins from later dynasties, such as Pharaoh Seti I (d. 1279 BCE), compared with earlier decan images, demonstrate the Sothic cycle shift.

According to Sarah Symons,

Although we know the names of the decans, and in some cases can translate the names (ḥry-ỉb wỉꜣ means 'in the centre of the boat') the locations of the decanal stars and their relationships to modern star names and constellations are not known. This is due to many factors, but key problems are the uncertainty surrounding the observation methods used to develop and populate the diagonal star tables, and the criteria used to select decans (brightness, position, relationship with other stars, and so on).

These predictable heliacal re-appearances by the decans were eventually used by the Egyptians to mark the divisions of their annual solar calendar. Thus the heliacal rising of Sirius marked the annual flooding of the Nile.

This method 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 Hellenistic astrology arose in Alexandria, recorded principally in the work of Ptolemy and Vettius Valens, various systems attributing symbolic significance to decans arose and linked these to the classical planets: the "wandering stars" Mercury, Venus, Mars, Jupiter and Saturn and the "lights", the sun and moon. Decans were connected, for example, with the winds, the cardinal directions, the sect (day or night) male and female, as well as the four humours (elements;) also these were hermetically considered linked 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 Decan (astrology)); and correlated with astrological signs.

Decans are named in various Greco-Egyptian sources, many Hermetic writings, the Testament of Solomon, the Tabula Aristobuli (Codex Palatinus) attributed to Aristobulus of Paneas, and the writings of Julius Firmicus Maternus, Cosmas of Maiuma, Joseph Justus Scaliger, and Athanasius Kircher.

Images of the decans are described in Hermetic writings, by the Indian astrologer Varāhamihira, in the Picatrix, and in Japanese writings. Varāhamihira's images of the decans was influenced by Greco-Egyptian, if not Hermetic, depictions of the decans by way of the Yavanajataka. Their role in Japanese astrology may have derived from an earlier Chinese or Indian form possibly from adding the twelve animals of the Chinese zodiac to a list of twenty-four hour stars. They were most common between the Kamakura and Edo periods.

The first original decan position due to the precession in ancient times started at 0° of Cancer when the heliacal rising of Sirius (Egyptian Sepdet; Greco-Egyptian: Sothis) before sunrise marking the Egyptian New Year which fell at 0° of Leo at July 20 in the Julian calendar, that is July 22/23 on the Gregorian calendar.

Western Zodiac Decan Original Decan Position due to the Precession in Ancient Times Ancient Egyptian
(Budge) Greco-Egyptian Testament of Solomon Aristobulus's names Greek Hermeticism Latin Hermeticism Firmicus Cosmas Scalinger Kircher Aries 1 28 Khent-kheru ⲭⲟⲛⲧⲁⲣⲉ
Χont-har Rhyax or Ruax Bendonc Chenlachori Aulathamas Senator or Asiccan Aidoneus Asiccan Arueris (ⲁⲣⲟⲩⲉⲣⲓⲥ) 2 29 Qeṭ ⲭⲟⲛⲧⲁⲭⲣⲉ
Xont-χre Barsafael Mensour Chontaret Sabaoth Senacher or Asenter Persephone Senacher Anubis (ⲁⲛⲟⲩⲃ) 3 30 Sasaqeṭ ⲥⲓⲕⲉⲧ
Si-ket Artosael or Arôtosael Carexon Siket Disornafais Sentacher or Asentacer Eros Acentacer Horus (ⲱⲣⲟⲥ) Taurus 4 31 Ārt ⲭⲱⲟⲩ
Xau Horopel Gisan Soou Jaus Suo or Asicat Charis Asicath Serapis (ⲥⲉⲣⲁⲡⲓⲥ) 5 32 Khau ⲉⲣⲱ, ⲁⲣⲟⲩ
Arat Kairoxanondalon or Iudal Tourtour Aron Sarnotois Aryo or Ason die Horen Viroaso Helitomenos (ⲉⲗⲓⲧⲟⲙⲉⲛⲟⲥ) 6 33 Remen-ḥeru-an-Saḥ ⲣⲉⲙⲉⲛⲁⲁⲣⲉ
Remen-hare Sphendonael Ballat Rhomenos Erchmubris Romanae or Arfa Litai Aharph Apopis (ⲁⲡⲱⲡⲓⲥ) Gemini 7 34 Mestcher-Saḥ ⲑⲟⲥⲟⲗⲕ
Θosalk Sphandor Farsan Xocha Manuchos Thesogar or Tensogar Thetys Thesogar Tautus (ⲧⲟⲟⲩⲑ) 8 35 Remen-kher-Saḥ ⲟⲩⲁⲣⲉ
Uaret Belbel Vaspan Ouari Samurois Ver or Asuae Kybele Verasua Cyclops (ⲕⲟⲩⲕⲗⲟⲯ) 9 36 A-Saḥ
Phu-hor Kourtael or Kurtaêl Parquia Pepisoth Azuel Tepis or Atosoae Praxidike Tepisatosoa Titan (ⲧⲓⲧⲁⲛ) 37 Saḥ Cancer 10 1 (= 0' Cancer) Sepṭet ⲥⲱⲑⲓⲥ
Sopdet Metathiax Panem Sotheir Seneptois Sothis or Socius Nike Sothis Apollun (ⲁⲡⲟⲗⲗⲟⲩⲛ) 11 2 Ṭepā-Kenmut ⲥⲓⲧ
Seta Katanikotael Catarno Ouphisit Somachalmais Sith Herakles Syth Hecate (ⲉⲕⲁⲧⲏ) 12 3 Kenmut ⲭⲛⲟⲩⲙⲓⲥ
Knum Saphthorael or Saphathoraél Hellors Chnouphos Charmine Thiumis or Thumus Hekate Thuimis Mercophta (ⲙⲉⲣⲕⲟⲫϯ) Leo 13 4 Kher-khept-Kenmut ⲭⲁⲣⲭⲛⲟⲩⲙⲓⲥ
Χar-Knum Phobothel or Bobêl Jarea Chnoumos Zaloias Craumonis or Afruicois Hephaistos Aphruimis Typhon (ⲧⲟⲩⲫⲱⲉⲟⲩⲥ) 14 5 Ḥā-tchat ⲏⲧⲏⲧ
Ha-tet Leroel or Kumeatêl Effraa Ipi Zachor Sic Isis Sithacer Peroeus (ⲡⲉⲣⲟⲉⲟⲩⲥ) 15 6 Peḥui-tchat ⲫⲟⲩⲧⲏⲧ
Phu-Tet Soubetti Hayas Phatiti Frich Futile or Eisie Sarapis Phuonisie Nephthe (ⲛⲉⲫⲑⲏ) Virgo 16 7 Themat-ḥert ⲧⲱⲙ
Tom Katrax or Atrax Angaf Athoum Zamendres Thumis or Thinnis Themis Thumi Isis (ⲓⲥⲓⲥ) 17 8 Themat-khert ⲟⲩⲉⲥⲧⲉ—ⲃⲓⲕⲱⲧⲓ
Uste-bikot Jeropa or Ieropaêl Bethapen Brysous Magois Tophicus or Tropicus Moirai Thopitus Piosiris (ⲡⲓⲟⲥⲓⲣⲓⲥ) 18 9 Usthȧ ⲁⲫⲟⲥⲟ
Aposot Modobel or Buldumêch Baroche Amphatham Michulais Afut or Asuth Hestia Aphut Cronus (ⲕⲣⲟⲛⲟⲥ) Libra 19 10 Bekathȧ ⲥⲟⲩⲭⲱⲥ
Sob‿χos Madero or Naôth Zercuris Sphoukou Psineus Seuichut or Senichut Erinys Serucuth Zeuda (ⲍⲉⲟⲩⲇⲁ) 20 11 Ṭepā-khentet ⲧⲡⲏⲭⲟⲛⲧⲓ
Tpa-χont Nathotho or Marderô Baham Nephthimes Chusthisis Sepisent or Atebenus Kairos Aterechinis Omphta (ⲟⲙⲫϯ) 21 12 Khentet-ḥert ⲭⲟⲛⲧⲁⲣⲉ
Xont-har Alath Pieret Phou Psamiatois Senta or Atepiten Loimos Arpien Ophionius (ⲟⲫⲓⲟⲛⲓⲟⲥ) Scorpio 22 13 Khentet-khert ⲭⲟⲛⲧⲁⲭⲣⲉ
Spt-χne Audameoth Haziza Name Necbeuos Sentacer or Asente Nymphs Sentacer Arimanius (ⲁⲣⲓⲙⲁⲛⲓⲟⲥ) 23 14 Themes-en-khentet......
Sesme Nefthada Nacy Oustichos Turmantis Tepsisen or Asentatir Leto Tepiseuth Merota (ⲙⲉⲣⲱϯ) 24 15 Sapt-khennu ⲥⲡⲧⲭⲛⲉ
Si-sesme Akton Alleinac Aphebis Psermes Sentineu or Aterceni(-cem) Kairos (repeated) Senicer Panotragus (ⲡⲁⲛⲟⲧⲣⲁⲅⲟⲥ) Sagittarius 25 16 Ḥer-ab-uȧa ʿⲣⲏⲟⲩⲱ
Hre-ua Anatreth Ortusa Sebos Clinothois Eregbuo or Ergbuo Loimos (repeated) Eregbuo Tolmophta (ⲧⲟⲗⲙⲟⲫϯ) 26 17 Shesmu ⲥⲉⲥⲙⲉ, ⲥⲓⲥⲉⲥⲙⲉ
Sesme Enautha or Enenuth Daha Teuchmos Thursois Sagon Kore Sagen Tomras (ⲧⲟⲙⲣⲁⲥ) 27 18 Kenmu ⲕⲟⲛⲓⲙⲉ
Konime Axesbyth or Phêth Satan Chthisar Renethis Chenene or Chenem Ananke Chenen Teraph (ⲧⲉⲣⲁⲫ) Capricorn 28 19 Semṭet ⲥⲙⲁⲧ
Smat Hapax or Harpax Eracto Tair Renpsois Themeso Asklepios Themeso Soda (ⲥⲱⲇⲁ) 29 20 Ṭepā-semṭ........
Srat Anoster Salac Epitek Manethois Epiemu or Epimen Hygieia Epima Riruphta (ⲣⲓⲣⲟⲩⲫϯ) 30 21 Sert ⲥⲣⲱ
Si-srat Physikoreth or Alleborith Seros Epichnaus Marcois Omot Tolma Homoth Monuphta (ⲙⲟⲛⲟⲩⲫϯ) Aquarius 31 22 Sasa-sert ⲥⲓⲥⲣⲱ
Tpa-χu Aleureth or Hephesimireth Tonghel Isi Ularis Oro or Asoer Dike Oroasoer Brondeus (ⲃⲣⲟⲛⲇⲉⲟⲩⲥ) 32 23 Kher-khept-sert........
Xu Ichthion Anafa Sosomo Luxois Cratero or Astiro Phobos Astiro Vucula (ⲃⲟⲩⲕⲟⲩⲗⲁ) 33 24 Khukhu ⲧⲡⲏⲭⲩ
Tpa-Biu Achoneoth or Agchoniôn Simos Chonoumous Crauxes Tepis or Amasiero Osiris Tepisatras Proteus (ⲡⲣⲟⲧⲉⲟⲩⲥ) Pisces 34 25 Baba ⲭⲩ
Biu Autoth or Autothith Achaf Tetimo Fambais Acha or Atapiac Okeanos Archatapias Rephan (ⲣⲉⲫⲁⲛ) 35 26 Khent-ḥeru ⲧⲡⲏⲃⲓⲟⲩ
Xont-Har Phtheneoth or Phthenoth Larvata Sopphi Flugmois Tepibui or Tepabiu Dolus Thopibui Sourut (ⲥⲟⲟⲩⲣⲟⲩⲧ) 36 27 Ḥer-ȧb-khentu ⲃⲓⲟⲩ, ⲧⲡⲓⲃⲓⲟⲩ
Tpi-biu Bianakith Ajaras Syro Piatris Uiu or Aatexbui Elpis Atembui Phallophorus (ⲫⲁⲗⲗⲟⲫⲟⲣⲟⲥ)

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 drekkanas is mentioned earliest by Sphujidhvaja in Yavanajataka (269–270 CE), and given detailed treatment by Varahamihira 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.