DECANATES
-------
John Pazmino
NYSkies Astronomy Inc
www.nyskies.org
nyskies@nyskies.org
2008 August 31 initial
2019 June 28 current
Introduction
----------
From time to time I get an inquiry about the 'decans' or
'decanates' of the zodiac. I myself was curious from mention of the
decans in astronomy history. In traditional treatments of ancient
astronomy there are two major and distinct systems of decan. The older
system comes from Pharaonic Egypt as a celestial clock. The newer
decanates come from Greek astronomy and astrology.
The reek system was easier to understand because it is still used
today among astrologers.
The Egyptian system remained until this 21st century somewhat of a
mystery. One maddening feature of the Egyptian decanates was the lack
of a positive correspondence of the decans as gods and the actual
stars in the sky.
In the 2000s new Egyptian texts were unearthed and those in hand
yielded new interpretation. Now, in the 2010 we have a far fuller
understanding of the decans, with some solid results at matching the
with the stars.t the decans.
I summarize the new work on the Egyptian decanates and update the
material for the Greek ones. This present article is a massive
rewrite of the previous one, which is now thoroly ediurnate.
Hierogluphs
---------
Pharaonic Egypt developed a rhebus form of writing where small
pictures, the glyphs, represent sounds or words. On the monuments the
pictures are awesomely clean and detailed but handwritten hierogluphs
also can be handsome.
I should mention that in the 1980s I took a hierogluphs class
under a hieroglyphs master. I still have the textbook, reader,
dictionary, sample homeworks. The class was very challenging. It
demanded strict care and attention. In fact, that's how I first
learned about decans and other amazing features of Egyptian society.
Handling a hieroglyph text takes three steps. First is a
transcrition of the glyph in handwritten form. This is crucial when
the text is damaged or eroded. I never had to do this because I worked
from printed reproductions or typeset text.
Typeset? Yes, I have a hieroglyphs wordproc software. When a gluph
is selected, it prints on screen in a 'font' more or less standard in
Egyptology. it can be moved and sized to fit into its word. Like real
hieroglyphs the wordproc can deposit the text right-left or left-
right.
The next step is to translitterate the gluphs into the sounds with
phonetic spelling. There being only a couple vowel sounds in ancient
Egyptian, a filler 'eh' is inserted to pronounce the words. While most
of the trranslitteration uses Latin characters, a few invented ones
are needed for peculiar sounds. The translitteration paces the
direction of the hieroglyphs and are written fornward or backward as
appropriate.
The last step is to translate the text into some sensible clear
English, which is easier said than done with the numbing stiffness of
phrasing. It reminded me of the stultifying boilerplate of Soviet
litterature. Mind well that the hieroglyphs we have are overwhelmingly
the written on the monuments in officious tone.
Here's where it really helps to be an bidirectional, like some
early computer printers. Right-left text called for right-let mirrored
translitteration and translation.
With that in my background, the inquiry into Egyptian astronomy
was both easier than otherwise and orders more fun.
Egyptian astronomy
----------------
When we speak of 'Egyptian astronomy' we mean the profession
practiced by a corps of officials in the king's court. They were
trained and exercised to look after the fate and fortune of the
kingdom thru omina and signa including those in the heavens.
The man-in-the-street had nothing to do with the stars, except for an
ignorant contemplation.
He relied on the skywatching officials to remind of upcoming holidays
and festivals and to warn of potential calamities.
. The layman was concerned with workaday chores. Maybe he sat by the
Nile in a summer breeze to admire the Moon or a bright
These officials were good observers of the heavens and made
careful records of celestial events. They did this in hopes of
foretelling the fate and fortune of Egypt. That is, the astronomy was
more divination, like for weather, animal behavior, fish and crop
yield, luck in warfighting.
There was no scholarly pursuit of astronomy, like during the
Greek or Babylonian world. Egypt had no 'scientific' endeavor for the
stars. There were only simple and naive ideas about the mechanics of
the sky.
The Sun, as example, was a ball of fire pushed along by a beetle.
A lunar eclipse occurred when the Moon slides behind the sky and is
veiled by it. A planet coming into view after solar conjunction was
born into a new life. Vision worked by invisible hands emitted from
the eyes to touch and feel their surrounds.
Egypt had no concept of a 'cosmos', 'planet orbits', '3D extent',
or even an abstract model.
In spite of the shallow science in Egyptian astronomy, their
records, preserved in monuments and papuri, are crucial for fixing
chronology, confirming historical events, monitoring the slowdown of
Earth's rotation.
Celestial gods
------------
Egypt was a polytheist society whose life was modulated by gods.
For this piece I discuss just the gods for planets and decans. These
were different from the other gods for being visiting or circulating
gods. They came to town on a certain day, do duty over Egypt for a
span of months, then departed town on a certain other date.
The arrival was the heliacal rising of the god in morning after
solar conjunction, explained further later. The god stayed in view
until it set heliacly in the evening.
Detailed accounts of visits of the planet gods enabled us early in
Egypt studies to confidently identify them and trace the planet
movements among the stars. The start, duration, end of each visit is
the planet's apparition period. The is a little shorter than the
synodic period because around conjunction the planet is out of sight
for a few weeks.
The other set of gods was the decans. These were 36 gods who were
not well explained until the 200s-2010s. They started their work at
10-day intervals in a definite sequence thruout the year. Each decan
come into town, served Egypt, and left town on the same dates every
year. When one was in service, the next one appeared to join it. One
other at the head of the sequence left town, his duty finished until
next year.
Decan gods
--------
The usual description of the Egyptian decanates is that they are a
set of stars or asterisms around the sky such that they rise at 40-
minute intervals during a night. r, at a given clock hour they rise 10
days apart. These were used to mark time during a night by noting how
many decans rose during a nighttime task or how many remained until
the one rising in dawn.
The impression, held by astronomers and Egypt scholars, was that
the decans are in a belt around the sky. One plausible belt was the
ecliptic but some suggested the equator. On the equator the decans
would be spaced about 10 degrees apart while on the ecliptic they were
irregularly spaced to accommodate the inclined rising of zodiac
constellations.
Here to fore efforts to associate the decan gods with particular
stars or asterisms were weakly successful. In fact, some Egypt
scholars suggested that the decans were only gods with out actual
correspondence with stars. Their visiting schedule was only a
schematic behavior.
Heliacal rising
-------------
Egypt began the day at sunrise, while many other contemporary
cultures started the fay at sunset. It paid special attention to
planet, and dean, activity along the eastern horizon. When a planet is
near conjunction with the Sun it is in bright daylight or twilight and
can not be seen i the sky. (We have no record of Egyptian skywatchers
spotting Venus by day.) After conjunction the planet edges away from
the Sun into a darker zone of twilight to begin its new synodic
cycle. It is still in twilight too bright to shine thru until several
days later.
On a certain day when the planet rises, it is in twilight just
dark enough to shine thru and it is sighted by the skywatchers. A
moment later the sky around the planet brightens as dawn progresses.
The planet is then lost in the bright sky. The date this occurs is the
date of heliacal rising.
On the next morning the planet edged a bit farther from the Sun
into twilight a bit darker than the previous night. When it rises the
sky stays dark enough to follow the planet for a few minutes, then it
is lost in advancing dawn. After a week or so the planet rises in a
dark sky, it being beyond the bright twilight glow of the Sun.
The planet slides farther into night, rising earlier and earlier
each morning until it is already in the sky at sunset. (I use a
superior planet here for simplicity.) After several months the planet
starts to set in twilight after sunset. It sets into ever brighter
twilight until on a certain day it is sighted at setting just as
twilight snuffs it out. This is the heliacal setting.
One crucial point to mind is that heliacal rising/setting is not a
determinate event. It depends sensitively on the observer's eyesight and
obscuring interference on the horizon, in addition to the stellar
brightness and color, of the planet. I suppose the heliacal rising of
Venus is more positively recorded than that of mars.
A clever suggestion by some scholars is that the heliacal
rising/setting was not physicly observed. They were reported by
projection from observed events on earlier or later days.
Starcharts
--------
In monuments Egypt placed charts of the heavens. The whole
celestial sphere visible from Egypt latitude was drawn, not a sky
dome for a given date and hour. The constellations, peculiar to Egypt,
were arranged geographicly on the chart in their stilted formal poses,
stereotypical of Egyptian inscriptions. No stars were marked. I'm not
sure if the size of the constellation creature was the area it
occupied in the sky or the relative title or rank among the gods.
The zodiac was recognizable from a few constellations carried
forward to later civilizations. In some cases the planet gods were
drawn in the zodiac, tucked within or between the constellations. By
studying such starcharts we can narrow the possible dates for it, the
structure it sits on, and the event it commemorates.
Now comes the kicker. The 36 decans, altho somehow associated with
the heavens, were arranged in a row next to or circle enclosing the
main chart. The order of the decans was the standard one from #1 to
#36. They had proper names, those of the gods, but I had to leave them
out in this piece. The ASCII translitteration of the hieroglyphs would
make no sense at all.
This consistent depiction of the decans on starcharts misleaded
astronomers and Egyptologists. Where do these decans fit in the sky?
Decan stars
---------
As we learned more about the decan gods we realized they were not
associated with stars along a single band. Their stars could be
anywhere along the eastern horizon. The Egyptians knew stars all over
the sky, not only along a particular belt, not even just the zodiac.
They aligned some temples to certain stars in various parts of the
heavens.
This mew knowledge about decans allowed scholars to so ernest
searches for the stars.They were strongly assisted by new astronomy
software that competently simulated the sky in long-ago eras.
We still do not know when, by chronology, or how, by physical
sighting, the decans were first established, They were in routine use
when the Middle Kingdom began about 2000BC And Egypt's latitude is
that of Karnak or Luxor, where many ceremonies for the celestial gods
were held.
I give here one such list, compiled by Conman in 'Discussions in
Egyptolohy', vol 54, 2006-2009. One bizarre source of decan
information is the inside lid of coffins! The lid often had a table
and list of decans associated with the deceased. The decan number is
based on the Asyut coffins, which Conmam studied for being the oldest
known example of decan tables and lists. They date from about 2000BC.
In the table I leave out the Egyptian names because they are
meaningless for those outside Egypt studies. We may call the decans by
the modern star name.
Before running outside to play with this table, There are two
important cautions. Firstly the decans are latitude-sensitive. The
list was compiled for Egypt Some decan stars don't rise at all in New
York's latitude. Some others are circumpolar or close to there..
The other caution is that precession changed the declination of
the decan stars. The Egyptians were affected by precession but had no
clue to its action. There are many buildings lining up with a certain
star when constructed but later modified to keep the aim as the star
shifted declination by precession.
To the Egyptians, and other cultures prior to Hiupparchus,
'something funny happened to the stars'. Thruout Egypt's history the
selection of stars for decans changed as one no longer fitting in the
sequence was replaced by a new one that did. The need for adjustments
was almost all due to precession. A skyeatcher could merely believe
the ill-fitting decan star was a poor choice to begin with.
------------------------------------------------------
- | | heliac | zodiac
decan | star | rise | hyposoma
------+------------------------------+--------+-------
1 | Arcturus | 17 Sep | Vir II
2 | Spica | 25 Sep | Vir III
3 | Alphecca, iot Cen | 7 Oct | Lib I
4 | Z'shemali, Z 'genubi, Menkent | 17 Oct | Lib II
5 | Hadar | 27 Oct | Lib III
6 | Antares | 7 Nov | Sco I
7 | Rasalhague, Sabik, eps Sco | 16 Nov | Sco II
8 | Vega, Shaula, Sargas | 26 Nov | Sco III
9 | Kaus australis | 4 Dec| Sgr I
10 | Nunki | 11 Dec | Sgr II
11 | Altair | 20 Dec | Sgr III
12 | Deneb, Dibah Algedi | 29Dec | Cap I
13 | [apparently none] | 7 Jan | Cap II
14 | Enif, Sadalsud | 16 Jan | Cap III
15 | Sadalmalik | 26 Jan | Aqr I
16 Markab, Scheat | 5 Feb | Aqr II
17 | Schedar, Alpheratz | 15 Feb | Aqr III
18 | Fomalhaut, Algenib | 26 Feb | Psc I
19 | Mirach | 7 Mar | Psc II
20 | Almach | 17 Mar | Psc III
21 | Mirfak | 26 Mar | Ari I
22 | Hamal, Sheratam Dipha | 7 Apr | Ari II
23 | eps Per | 19 Apr | Ari III
24 | Capella | 29 Apr | Tau I
25 | Menkalinan, Menkar | 12 May | Tau II
26 | Aldebaran | 22 May | Tau III
27 | Alhecka, Thabit, Rana | 3 Jln | Gem I
28 | Castor, Bellatrix | 13 Jun | Gem II
29 | Rigel, Pollux | 24 Jun | Gem III
30 | Procyon | 7 Jul | Cnc I
31 | Sirius | 17 Jul | Cnc II
32 | Regulus | 28 Jul | Cnc III
33 | Alphard, Zosma | 7 Aug | leo I
34 | Denebola | 17 Aug | leo II
35 | Zavijava, nu Hya | 27 Aug I Leo III
36 | Vindemiatrix, Canopus | 6 Sep | Vir I
----------------------------------------------------
While this is a plausible correspondence between decan gods and
stars, there are several instances of two or three candidates. And
Gonman apparently didn't find a good candidate for decan #13. I see
similar uncertainties in some other new Egyptian litterature.
I replaced many of Conna's Bayer star stars with proper names. I
also left out extra columns with Egyptian names.
The last column 'zodiac hyposoma' (hih-PO-so-ma), with plural
'hyposomata (hih-po-SO-ma-ta), is an Egyptian feature dividing the
zodiac into 36 zones of 10 days each. They rise with the decan and
with the Sun a few minutes later. When a planet god sits in certain
hyposomata its power is enhanced or exalted. The hyposomata were
carried forward into Greek astronomy to become the modern decanate
system. They are today named i-3, I-III, within each zodiac sign.
Egyptian planets
--------------
I digress to deal with the planet gods in Egypt. They were, like
the decan gods, always ranked in the same order as a group. The decan
sequence was the order of heliacal rising, one after the other.
The planets of Egypt were Venus, Mercury, Mars, Saturn, Jupiter.
Egyptian starcharts sometimes placed thee planet gods in a queue or
row outside the chart. The creatures are lined up in the same order,
Venus thru Jupiter.
The close match with the Greek and later astronomy suggested that
the Egypt had some hidden knowledge of the solar system or other
spatial model of the cosoms. This order endured thruout the Egyptian
eram right up to the arrival of Alexandef in the 300s BC.
Thanks to newlu found texts, clearer interpretations, matured
astronomy software, we learned that the planet sequeence came from an
amazing convention of planets in February-March 1953BC.
Egyptian calendar
---------------
The Egyptians had two calendars, one for civil functions and one
for ceremonies. The civil calendar had twelve months of 30 days, plus
5 yearend holidays. These filled the 365 days of the year. The
leftover 1/4 day was ignored and there was no leapday adjustment.
The months were grouped into three seasons, four to each, aligned
with the agricultural life of Egypt. They are commonly named
'inundation' for the period of the Nile flooding, 'growing' for the
planting and tending of farms, 'harvesting' for gathering the crops
and preparing them for market. The five yeared holidays celebrated an
other year of successful life.
The calendar cycled thru all the dates in 1460 years, but there
was little ambient weather or climate activity to worry about the date
drift.
The ceremonial calendar continued a practice common tn northern
Africa and mid East of starting each month by actual observation of
the Moon. its twelve lunar months made a lunar year, short of the
solar year by some ten days. Every couple years an extra month was
added to get the two more or less back in synch. This adjustment seems
to be irregular, making chronology of dates expressed in this calendar
difficult,
One peculiar feature of both Egyptian calendars is that the day
began at sunrise, not the more usual sunset. This was part of the Nile
geography. The west, left, side faced the endless empty Sahara desert,
with no access to trade or war with other peoples. Egyptians venturing
innocently into the desert often perished.
The right, east, side faced the Red Sea with its access to trade
and war in the Mid East. This side was handy to forests and elevation
for hunting, recreation, relief from summer torridity.
It was just easier to live on the right side to avoid always
having to cross the river from the west side. Recall that until the
20th century, when bridges and tunnels were built, the only way to
cross the Nile was by boat.
Over time te west side was regarded as a place of death, with only
temporary occupation allowed for work or visit. This side is for the
necropolities like Pyramids and Valley of the Kings.
In the east, over the living side of Egypt, the rising Sun brings
in its light and heat and life. The setting Sun, over the west death
side, takes all of this away.
The setting Sun was a time of death. The rising Sun was the start
of the new day of life.
The month in the cultural lunar calendar began with the last
sighting of the waning crescent Moon before sunrise. This event was
easier to definitely determine by riding the waning Moon night by
night until its visual or anticipated last appearance. The convention
of 1953BC occurred at the start of an Egyptian month with the last
crescent Moon joining the planets in early March of the year.
Dating ancient events
-------------------
Long-ago dates in modern litterature are expressed in modern form.
But the modern months and days weren't established until the Roman
era. With each ancient society using its own calendar, it is a chore
for scholars to mesh the calendars together into a uniform
chronological scheme. One immense tool is astronomy. Astronomical
events like eclipses can be retrodicted and link to the original
specification of date.
To apply a modern date system to ancient events, we extend the
Julian calendar, developed by Julius Caesar and fixed up by Augustus
Caesar, into the past. It adds a leapday every fourth year. I better
note that the divide-by-four was not part of the Caesars's plan. Our
current year count didn't start until the mid 500s AD. When cycled
back to the initial year of the repaired Julian Calendar, the year
number was 8AD. That's where the 'divide-by-four' comes from.
The rule fails for the 'BC' year count, before 1AD, but works
for the 'algebraic' count that includes a year numbered zero.
Altho the statement of date helps us to picture when within a year
the event occurred, it can not alone tell when it happened within the
original Egyptian year. Other information about the event is needed,
such as from cicumstant text.
Major advances in ancient chronology came in the 1990s with
maturation of Earth rotation slowdown and computer simulations. We
use, among others, eclipses of Sun and Moon to learn where they were
observed, as recorded in contemporary texts. The modern retrodictions
link the local records into the modern date scheme.
Nile flood
--------
Allied to calendar in Egypt was the annual flood of the Nile that
deposited fresh topsoil onto its banks, renewing the land for
agriculture. In climatic spring rain in east-central Africa, in the
mythical Montes Lunae, fell in humongous volume. The water flowed into
the headwaters of the Nile, carrying with it fertile African soil.
After several months the water reached the last of several shoals or
rapids, the Cataracts, and entered the Egyptian land. This last rapids
was at Aswan, at the Egypt-Sudan border.
The Nile also brang silt and clay that went into the delta. Today
we understand that this material stabilizes and sustains the delta
against erosion. Egypt harvested the clay to make bricks, pottery,
other small durable items.
The land bordering the Nile is gently sloped. The soil-filled
flood flowed outward for hundreds of meters before continuing on to
the delta, at modern Cairo. Thenafter it dispersed thru the delta and
into the Mediterranean Sea.
The flood was anticipated by noting the last heliiacal decan
before hand, based on previous experience. According as instant phase
of precession, the heliacal rising of decan datr Sirius alerted Ehupt
to send monitors to the First Cataract. In 2000BC this occurred in
the mid to late July, with the waters reaching Cairo by late August.
The flood came every year, as weather permitted in the headwaters.
Some years had strong flood; others, weak. The arrival of high water
wandered, being sooner or later than expected. The year-to-year
variation in timing and strength of flood was a major concern to
Egypt.
The flood was absolutely critical for the well-being of Egypt!
Soonest the high water was spotted at the First Cataract (named in the
upstream order) word was flashed along the river to prepare for the
flood. It took a month for the high water to reach Cairo and the
delta.
When the river returned to its banks and solar heat dried out the
new soil, the building of farms began. A deep layer of soil produced
plentiful food and graze crops.
The flood zone flanking the Nile was off-limits for permanent
structures. All buildings were placed on higher ground above the
normal crest elevation. Only minor exceptions, like a road from a boat
dock, were permitted.
1953 BC
--- -
For many decades before about 2000BC. some geologists suggest over
a century, the Nile floods were weak, depositing thin soil and Farming
yielded poor crops, causing general hard life and low activity in
Egypt's society. The Egyptians did not know how or why the Nile
flooded, only that it did by some action of the gods. They took the
fate as was and
offered appreciations to their deities.
By the early 1900s BC, by a climate shift, the floods started to
strengthen and Egypt prospered again. In February-March of 1953BC, or
-1952 algebraic, the skywatchers were awed by a fantastic phaenomenon,
a convention of all five planets in the dawn sky. The planets
gradually assembled above the sunrise point and compacted together.
On February 26 they were the tightest together within an arc of
only a couple degrees. Saturn was at the east end; Jupiter, west.
about in the middle was a clump of Mercury Venus, Mars.
The array unwinded in the following dawns until on March 2 the
waning crescent Moon joined it. At this time the planets were
spaced along an arc in order east to west: Venus, Mercury, Mars,
Saturn, Jupiter. This scene had a profound impression on the
skywatchers, witnessing all five planets, the Moon, and in a few more
minutes the Sun. And this scene must have something to do with the
recent return of life-saving floods in the Nile.
From then on, until Egypt was overtaken by Greece, this same order
of planets was maintained.
Conventions of the five planets, with or without the Moon are
surprisingly common. We had several in the 2000s and 2010s in both
dawn and dusk sky. The sequence of planets was jumbled relative to
their order in the solar system. The convention of 1953BC seems to be
the most compact -- and visually spectacular -- of all since then.
I warn that to simulate this, and other deep past astronomy events,
the software must have a strong ephemeris engine. Some programs go off
the rails beyond a millennium or so ago. It may be better to try a
solar system simulator first rather than a planetarium.
You missed it?
------------
If you're thoroly despondent for missing this grand convention (it
was snowing?), an other tight one comes about 4,000 years later.
That's about right now!
By being young now (in 2020) and staying healthy, you can see a
convention almost as incredible as the one you missed. In the first
week of September 2040AD the five planets and waxing crescent Moon
converge in the western sky at dusk. Longitude affects the exact
position of the Moon at local dusk.
The arc is about 9 degrees, twice that of 1953BC, yet it's the
shortest in modern times. The other five-planet gatherings of this
century so far, in 2020, were spread over arcs of 10s of degrees.
The planets juggle around over the days with the Moon abeam of
them on september 8th. At no time do the planets line up in solar
system order or close to it.
Greek stars
--------
The early Greeks, long before they developed their own astronomy,
kept Egypt's planet order and division of the zodiac into decans. From
latitude and precession effects they discarded the off-zodiac decans,
both stars and deities.
The Greeks over time built the constellations to the set we use
today. The stars were not attached to particular deities, as for the
Egyptians. The stars honored cultural heros and objects with no
celestial influence on Earth.
There are 48 constellations, 12 in the zodiac and 36 others. We
keep all of them except Argo Navis. It was in the 1930s broken into
four smaller constellations: Carina, Puppis, Pyxis, Vela. Pyxis is a
faint group with its own brand-new Bayer stars. The other three share
the original Argo set of Bayer stars. There is no 'gamma Carinae', it
being gamma Velorum, for example.
Coma Berenices was inconsistently recognized in Greece. It came
into general use in mediaeval times. Crux was split off from Centaurus
in the 1600s.
The Romans preserved the Greek constellations, renaming them into
Latin, sometimes with modified stories for them. We use the Latin
names today. Some languages translitterate or translate the names into
their own tongue.
The Greeks shuffled the planet sequence for their angular speed
thru the zodiac. The order became Saturn (slowest), Jupiter, Mars,
Sun, Venus, Mercury, Moon (fastest). When the Greeks devised a spatial
model of the world, Saturn was the highest, farthest, from Earth. The
other planets in order were closer. The Moon was closest not only
speed but also by showing parallax from different places on Earth and
coming in front of the other planets.
Greek decans
----------
The Greeks straightened the Egyptian zodiac decans into 36 10-
degree slices of the zodiac, three to a sign. These decans have no
interaction with off-zodiac stars/gods. The decanates are numbered 1
to 3, or I to III, downstream in each sign. Occasionally they are
called the first, middle, last decan of a sign.
Without the god/star pantheon of Egypt the zodiacal decans at
first had no function except as places where the planets exerted
stronger influence when sitting in certain ones.
The Greeks felt there had to be some attachment of nonzodiac
constellations to the zodiac. They assigned a nonzodiac constellation
to each decan, three per sign. Each decan 'looked after', 'took care
of', 'minded' its constellation. Ideally the constellation for a decan
was in the decan's ecliptic longitude zone. Since constellations had
irregular size and shape and had no definite borders, this scheme was
not well carried out. The three constellations for each sign were at
least mostly north and south of the sign.
Today the decan assignments are offset by precession, sliding the
decans westward from their original zodiac constellations. Attempts in
modern times came and went to build a new assignment. I gave one
example of a modern realignment in previous editions of this article
but readers explained that there is no agreement among astrologers for
new decan assignments. Here I keep only the original arrangement.
In addition to the constellation allocation among decans, each
decan had a planet whose power was enhanced when passing thru it. The
sequence followed that of the spatial order, Saturn thru Moon.
The table below shows the Greek decans, with the dates the Sun is
in each during the year. These are Gregorian dats, with the
modification of the leapday scheme cranked in.
-------------------------------------------------
zodiac lon : solar dates : planet : constellation
------------+-----------------+----------+---------------
ARIES /
000d - 009d : Mar 21 - Mar 31 : Mars : Triangulum
010d - 019d : Apr 1 - Apr 10 : Sun : Eridanus
020d - 029d : Apr 11 - Apr 19 : Venus : Perseus
--------------------------------------------------
TAURUS
030d - 039d : Apr 20 - Apr 30 : Mercuty : Lepus
040d - 049d : May 1 - May 10 : Moon : Orion
050d - 059d : May 11 - May 20 : Saturn : Auriga
------------------------------------------------
GEMINI
060d - 069d : May 21 - May 31 : Jupiter : Ursa Minor
070d - 079d : Jun 1 - Jun 10 : Mars : Canis Major
080d - 089d : Jun 11 - Jun 20 : Sun : Ursa Major
----------------------------------------------------
CANCER
090d - 099d : Jun 21 - Jun 30 : Venus : Canis Minor
100d - 109d : Jul 1 - Jul 11 : Mercury : Hydra
110d - 119d : Jul 12 - Jul 22 : Moon : Argo Navis
----------------------------------------------------
LEO
120d - 129d : Jul 23 - Aug 1 : Saturn : Crater
130d - 139d : Aug 2 - Aug 12 : Jupiter : Centaurus
140d - 149d : Aug 13 - Aug 22 : Mars : Corvus :
------------------------------------------------
VIRGO
050d - 159d : Aug 23 - Sep 1 : Sun : Bootes
060d - 169d : Sep 2 - Sep 12 : Venus : Hercules
170d - 179d : Sep 13 - Sep 22 : Mercury : Corona Borealis
----------------------------------------------------
LIBRA
180d - 189d | Sep 23 - Oct 2 : Moon : Serpens
190d - 199d : Oct 2 - Oct 13 : Saturin : Draco
200d - 209d : Oct 14 - Oct 22 : Jupiter : Lupus
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SCORPIUS
210d - 219d : Oct 23 - Nov 1 : Mars : Ophiuchus
220d - 229d : Nov 2 - Nov 11 : Sun : Ara
230d - 239d : Nov 12 - Nov 21 : Venus : Corona Australis
-----------------------------------------------------------
SAGITTARIUS
240d - 249d : Nov 22 - Dec 1 : Mercury : Lyra
250d - 259d : Dec 2 - Dec 11 : Moon : Aquila
260d - 269d : Dec 12 - Dec 21 : Saturn : Sagitta
--------------------------------------------------
CAPRICORNUS
270d - 279d :Dec 22 - Dec 31 : Jupiter : Cygnus
280d - 289d : Jan 1 - Jan 10 : Mars : Delphinus
290d - 299d : Jan 11 - Jan 19 : Sun : Piscis Austrinus
-----------------------------------------------------------
AQUARIUS
3]09d - 219d : Jan 20 - Jan 29 : Venus : Equuleus
310d - 319d : Jan 30 - Feb 8 : Mercuty : Pegasus
320d - 329d : Feb 9 - Feb 18 : Moon : Cetus
-----------------------------------------------
PISCES
330d - 339d : Feb 19 - Feb 28 : Saturn : Cepheus
340d - 349d : Mar 1 - Mar 10 : Jupiter : Andromeda
350d - 359d : Mar 11 - Mar 20 : Mars : Cassiopeia
----------------------------------------------------
There are 7 planets cycling 5 times thru 35 zodiacal decans. The
leftover 36th decan goes to Mars, as if to begin a 6th cycle. Mars has
two adjacent decans, the last of Pisces and first of Aries.
Modern use of decans
------------------
Altho precession skewed the signs away from their assigned decan
constellations, the zodiac constellations were not altered. we can let
the constellations attached to sign Aries be now attached to
constellation Aries. We end up with a clever method of star
recognition. Each zodiac constellation has a group of three nonzodiac
constellations around it.
We can learn the stars by groups of four across the sky, month by
month. For example, constellation, not sign, leo is associated with
Crater, Centaurus, and Corvus. Sightlines from Leo can be set up
toward each of these to find them in the sky. I know that Crater is a
dim constellation, easily missed in gray skies, but it is one of the
core 48 ancient constellations. Also, in mid north latitudes only the
north portion of Centaurus shows above the horizon, losing the
Centauri and Southern Cross.
This learn-bu-group fails completely in far south skies simply
because there was no astronomy in those latitudes that correlates to
the classical cultures.
Conclusion
--------
This present article is a wholesale revamp of previous ones,
taking into account newer work in Egypt studies. I expanded the
sections on Egypt to elaborate on the two meanings of 'decan', not
well known before.
Simulations of the Greek and Egypt sky, or any other in deep past,
require a strong solar system simulator program. Some planetarium
softwares have ephemeris engines that can accurately model past
celestial events. Some do not because the are designed for time spans
near the present .
While the egyptian decan stars ae of no use today, it can be
possible to build a modern set tailored to latitude and precession
epoch. Else treat them as part of the legacy of skywatching 4
millennia ago. The zodiac decans could be useful in learning the
arrangement of the constellations in sets of four. They are he zodiac
sign and its three satellites.
for me this exercise in learning about the Egyptian decans was
both exciting and fun from my own excursion into hieroglyphs in the
1980s. perhaps a reader had an episode, like in school or business,
apparently of little future worth. Then years or decades later it
comes back as a tool in an current astronomy situation