Twelfth-Parts | 1. Introducing the Dodecatemory of the Signs

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There is a secret key to the zodiac. Inside every zodiacal sign there are another twelve-signs. This division of the zodiac dates back to Babylonian times and was a key element of Hellenistic and early medieval astrology, but is extremely neglected today. Key elements of natal delineation and timing have been lost due to ignorance regarding this important feature of the zodiac. In this article, I explore the origins and use of twelfth-parts.

Pray examine now a matter trivial in appearance, yet one of great moment, which does not permit description of itself save by a Greek word.  I speak of the dodecatemories, of which the name proclaims the principle.  The signs each consist of thirty degrees, and every total is further divided by twice six; the calculation therefore shows that in each division there are two and a half degrees.    (Manilius, Book 2, 693-700, Goold trans., 1977, p. 137)

Who Used the Twelfth-Parts?

Hellenistic Astrologers

In addition to Manilius, the twelfth-parts were used by almost every Hellenistic astrologer. Early Hellenistic astrologers who used twelfth-parts include Dorotheus of Sidon (1st Century CE) in Book I, Ch. 8 and other sections of Carmen, Ptolemy (2nd Century CE) in Book I, Ch. 22 of the Tetrabiblos, and Vettius Valens (2nd Century CE) in multiple sections of his Anthology. Julius Firmicus Maternus (4th Century CE) strongly advocated the use of twelfth-parts in Book II, Ch. 17, and many other sections of his Mathesis. Additionally, Porphyry of Tyre (3rd Century CE) in Ch. 39 of his Introduction to the Tetrabiblos used twelfth-parts, as did Hephaistio of Thebes (5th Century CE) in Book I, Ch. 18 and in Book III of his Apotelesmatics. Rhetorius (7th century) also used twelfth-parts in Ch. 18 of his Compendium.

Early Medieval Astrologers

The twelfth-parts continued to be a basic component of astrological technique as practiced by later Perso-Arabic astrologers of the early medieval period, including Sahl, Masha’allah, Abu Ma’shar, al-Qabisi, Abraham Ibn Ezra, and more.

Abu Ma’shar made extensive use of twelfth-parts in his predictive methods. He made over 20 mentions of twelfth-parts in his work on predictive natal astrology, On the Revolutions of the Years of Nativities. Ma’shar advocated their use in nearly all predictive techniques. He explicitly advocated their use in solar returns (see Book I, Ch. 5-6; see Book II, Ch. 3 in relation to the profected Ascendant), lunar returns (see Book II, Ch. 1), primary directions (see Book III, Ch. 1), and transits (see Book V, Ch. 9). The twelfth-parts are key not only to natal delineation but also to predictive astrology.

Pre-Hellenistic Use

However, the use of the twelfth-parts predates Hellenistic astrology.  The twelfth-parts. like the twelve-sign zodiac itself, have their origins with the Babylonians, who used them in omen lore at least as far back as the 5th century BCE. Therefore, the twelfth-part divisions of the zodiacal signs are nearly as old as the regularized twelve-sign zodiac itself.

What are the Twelfth-Parts?

The twelfth-parts appear in the earliest strains of Hellenistic astrology. They are also known as dodecatemory/dodekatemoria,  duodena/duodecimae, or dwad/dwadashama. As the 1st Century astrologer, Manilius, explained in the opening quote, the twelfth-parts are divisions of each astrological sign into 12 equal parts. Each of the twelve parts are assigned a zodiacal sign beginning with the greater sign itself.

Finding Twelfth-Parts

Some authors, including Manilius, give two ways to calculate these, both leading to the same result. One way is to think of the first 2.5° as belonging to the sign itself, the second to the next sign, and so on until you get to the last 2.5° which belongs to the sign preceding the greater sign.  For instance, if Mercury were found at 28° Scorpio, then it would be in the last 2.5° of the sign, and thus its twelfth-part would be Libra.

A second method is used for greater accuracy. We take the degrees and minutes of the position within the sign and multiply it by 12, then add that many degrees to the beginning of the sign the planet is in.  For instance, with Mercury at exactly 28°00′ Scorpio, we would take 28 and multiply it by 12, yielding 336, then we would add this to the beginning of the sign Scorpio, so 30 would bring us to Sagittarius, 60 to Capricorn, 90 to Aquarius, and so on until we get to Libra with 6 degrees left over; the twelfth-part of Mercury would therefore be 6°00′ Libra in this case.

Chart Calculation of Twelfth-Parts

The FREE, open-source, traditional astrology program, Morinus, has twelfth-part calculation built-in. Some of the developers of the program have been very kind to me and gave given me the chance to check out the functionality before it was implemented.  It is great to have a program that can lay out the twelfth-part positions quickly and visually, because as we’ll see, these positions are informative and early astrologers placed importance on them.

Morinus Dodecatemoria
Morinus Chart Appearance Options

In order to pull up twelfth-parts in Traditional Morinus, after installation using the instructions I’ve provided, first pull up a chart. Then hold Shift and press A, or click on Option from the top navigation menu and click Appearance I. Select Dodecatemoria from the In Chart options and click OK. The chart will then have the twelfth-part positions apparent around the outside.

Bruce Lee TwelfthParts
Bruce Lee’s Natal Chart with Twelfth-PartsVariations

Some Variations

Manilius Division

Manilius asserted that the twelfth-parts are further divided into 5 segments of half a degree each, assigned to the five non-luminary planets, Saturn, Jupiter, Mars, Venus, and Mercury (see Manilius, Astronomica, Book 2, 738-748).  However, Manilius didn’t specify the order that the planets are assigned to these subdivisions, and no other early astrologers addressed these divisions.  Typically, the Chaldean order, either from slowest to swiftest (Saturn, Jupiter, Mars, Venus, Mercury) or the reverse (Mercury, Venus, Mars, Jupiter, Saturn) is suggested.  While the first one of these orders is certainly the most logical, supported by the use of such order in many other types of zodiacal division from decan to monomoiria, we can’t be sure. I don’t recommend the use of these subdivisions in practice.

Paulean Thirteenth-Parts?

It is also worth noting that Paulus Alexandrinus (4th Century CE) provided an idiosyncratic type of twelfth-parts. The twelfth-part explanation in Paulus is most likely in error, as he multiplies the position by 13, rather than by 12.  He gives a paragraph explaining his justification for multiplying by 13 rather than 12, but there isn’t much logical sense in the explanation in my opinion. Paulus seemed to imply that multiplication by 13 was necessary to allow the 12th parts to come back to the sign that the planet is in. This is hardly a noteworthy argument, as the first 2.5° of the sign already fall to that same sign in the standard system.

Commentary on Paulus

In the commentary on Paulus by Olympiodorus the Younger (6th Century CE), he found it necessary to explain the more typical form of twelfth-part first to preface the discussion. He then explained the idiosyncratic Paulean form. As far as I know, this idiosyncratic form of twelfth-part isban innovation of Paulus and was used by Paulus only, so I will not pursue it further here.

And we say: the ancient Egyptians used to call it the 12th part, since the number is found in the position of each star multiplied by 12.  However Paulus, having come later and examined the matter closely, [said] that the multiplication by 12 is never returned to the same zoidion where the star is, where we seek the dodekatemorion — but often the dodekatemorion of the star happens to fall in the same zoidion where the star is.   (Olympiodorus, Commentary on Paulus Alexandrinus, Ch. 21, Greenbaum trans., 2001, p. 102)

How were Twelfth-Parts Used?

The twelfth-parts produce a secondary zodiacal position for each planet and point in the chart. It is as if each point is projected into an additional hidden zodiacal position.

There are four main ways in which the twelfth-parts were used in Hellenistic astrology: 1. The twelfth-part of the Moon gave indications regarding the physical sex of the person; 2. The twelfth-part of the Sun gave indications about the Ascendant when it was unknown; 3. The twelfth-part of the Ascendant revealed thoughts/intentions; 4. Twelfth-part positions gave additional information about planetary significations that are on par with the natal positions of the planet.

I will briefly explore three of these four uses; for sex, finding the Ascendant, and interpretation of cognition.  However, I want to make it clear to the reader, that the last use is by far the most fruitful and important.

Sex of a Person from the Natal Chart

Both Dorotheus (Book I, Ch. 8 of Carmen) and Valens (Book IX, Ch. 8 of Anthology) used the sex of the sign of the twelfth-part of the Moon for delineation of the native’s sex.


For Dorotheus, the basic idea is that if the Moon’s twelfth-part is in a male sign (i.e. a Fire or Air sign) then the native is male, but if in a female sign (i.e. an Earth or Water sign) then the native is female.  However, there are some exceptions that can override this indication of the sex of the sign of the twelfth-part of the Moon.

The exception are as follows: 1. Sun, Moon, and Ascendant are in signs of the opposite sex, 2. the Light of the opposite sex (i.e. Sun is masculine and Moon is feminine) is in the Ascendant in a sign of its same sex, 3. planets of the opposite sex occupy the 1st and the 7th, 4. both Lights are in signs of the opposite sex and a planet of the opposite sex rules the Ascendant (example given is of both Lights in masculine signs and Jupiter ruling the Ascendant, this overriding a feminine twelfth-part of the Moon to indicate a male child).


For Valens, the sex of the sign of the twelfth-part of the Moon and the sex of the sign occupied by that sign’s ruler give strong indications for sex of the child.


This method is poor for predicting sex.  For instance, Kurt Cobain has Sun, Moon, and Ascendant all in feminine signs, which would override the fact that the twelfth-part of the Moon in his chart is in Sagittarius, a masculine sign.  Additionally, the ruler of the twelfth-part of the Moon is Jupiter, which is also in a feminine sign.

Cobain's Natal Chart
Cobain’s Natal Chart

One might argue that perhaps Dorotheus was incorrect and the twelfth-part of the Moon should be given the primary consideration in this endeavor. However, examine the chart of Traci Lords. Her Ascendant is in a masculine sign, Sun and Moon in feminine signs. The twelfth-part of the Moon is in a masculine sign, and its ruler, Saturn, is also in a masculine sign, so if they were given primary consideration we’d judge her to be a man.

Traci Lords' Natal Chart
Traci Lords’ Natal Chart
Junk Technique

In conclusion, we cannot rely upon the twelfth-part of the Moon methods of Dorotheus or Valens to guess the sex of a person by the birth chart. Perhaps Dorotheus and Valens have given us leads for the eventual development of a technique for guessing the sex of an individual from the chart that involves use of twelfth-parts. So far we don’t have a reliable technique for such a determination.

Twelfth-Parts for Finding the Ascendant

Another one of the more spurious uses of the twelfth-parts is to rectify the sign of an individual’s Ascendant when it is unknown.  It is Valens that discussed this use of twelfth-part of the Sun in Book I, Ch. 4 and Book IX, Ch. 7 of his Anthology.  It is only one method among many rectification methods discussed by Valens.

The method involves first knowing if the person was born by day or night and knowing the Sun’s position accurately enough to be able to find the sign of its twelfth-part. The Ascendant for a day birth will either be the sign opposite the sign of the Sun’s twelfth-part, or one trine to that sign, with preference given to the “left” trine (i.e. the one that is 120° after the sign of the twelfth-part of the Sun). If it is a night birth, then it will be one of the signs opposite to these, again with the same preference.


For example, if someone was born with the twelfth-part of the Sun in Taurus, then for a day birth the most likely Ascendant would be Virgo, but could also be Scorpio or Capricorn. If a night birth then the most likely Ascendant would be Pisces, but could also be Taurus or Cancer.


I’m a day birth with the twelfth-part of the Sun in Taurus, and my Ascendant is none of the three relevant signs, nor any of the three signs for night births.  A technique that narrows the Ascending sign to one-fourth of the signs of the chart, but still doesn’t give you an accurate indication is not a very valuable technique.

Interpretation of Cognition

One of the more fascinating niche uses of twelfth-parts is in the interpretation of cognition. This use was common for consultation charts, and later in medieval horary astrology. The technique originates with unknown Indian astrologers and Hephastio of Thebes. Importantly, it was adoped by Masha’allah.  The basic idea is that the twelfth-part of the Ascendant gives indications about the thoughts and intentions of a native or a querent (the one asking the astrologer to divine the answer to a question). The native is really concerned about matters pertaining to the house represented by the twelfth-part of the Ascendant. The qualities and conditions of that place such as the quality of the sign, its domicile lord, and occupants of the sign are all relevant to the native’s true concerns.

The Search of the Heart

Dr. Benjamin Dykes explored this use of twelfth-parts in considerable depth in his translation of, and commentary on, Hermann of Carinthia’s “The Search of the Heart”.  I highly recommend this work of Dr. Dykes for those interested in delving into this use of twelfth-parts in greater depth. Dykes explores the technique in his introduction, translates a work which uses the technique, and provides commentary on that work. Additionally, he includes appendices with further discussion and translations, including a table of the entire 144 significations given by Hephastio for each twelfth-part of the Ascendant.

Horary Astrology

The primary use of this technique in medieval astrology was to anticipate a client’s area of concern. This usage appears to have started in Indian and/or Hellenistic use of consultation charts. This use of consultation charts preceded, and likely lead to, the development of horary astrology.

Masha’allah in On Hidden Things (from the Works of Sahl and Masha’allah translated by Dykes in 2008) suggested that the twelfth-part of the Ascendant provides the best indications regarding a querent’s intention in an horary reading. If a planet is in that place then you look to that place as signifying the person’s intention. If the place is empty then you look to the place of its ruler.

Masha’allah: Twelfth-Part Ascendant and its Ruler

In an example given by Masha’allah (the same example was given by Hermann of Carinthia centuries later but attributed to the Indians), the Ascendant was the 12th degree of Aries, which has its twelfth-part in Leo. As the Ascendant was in Aries, Leo was the 5th place from the Ascendant.  Leo was empty in the horary chart and the Sun was in Libra, the 7th. Masha’allah surmised that the question involved the 5th in the condition of the 7th or the 5th seeking the 7th. The indication was that of a child seeking a woman (or seeking the querent’s wife).

Masha’allah said that if the Sun had been in the 6th then it would’ve suggested a question about a sick child, and so forth.  As you can see the stress in this technique is primarily on the significations of the place/house. One can combine the significations of the place with its ruler, in the sense of the place being fulfilled by or meeting the condition of the ruler’s place. This is one of a few different techniques given by Masha’allah and later authors for interpreting the intentions of a querent.

Chart Projections

Used with natal charts the technique puts an interesting twist on the idea of personal focus and fulfillment.  The ruler of the Ascendant shows a particular pull towards a certain place in the natal chart. Consider its accompanying themes and significations. Similarly, the twelfth-part of the Ascendant and its ruler may reveal a personal emphasis for the individual.

In the next article on twelfth-parts, I’ll explore their use in natal delineation in more depth. I’ll draw heavily on Maternus, who found in twelfth-parts the secret to more accurate delineation. I highly recommend the use of the twelfth-parts of all chart factors. I also recommend their use in predictive astrology as advocated by Abu Ma’shar. However, let’s start by looking at twelfth-part of the Ascendant.

Hitler’s Twelfth-Part Ascendant

Hitler had the twelfth-part of the Ascendant in Leo with the greater malefic Saturn, in the bound of Mercury. It is in the networking and popularity-oriented 11th House (house of friends), in the sign of leadership, Leo. Its ruler, the Sun, was in the 8th, pertaining to death and harm. The twelfth-part of Hitler’s Sun is also in the 8th, and its ruler too is in the 8th. This gives interesting additional valuable information that we can add to our knowledge that his Ascendant lord (Venus) and the sect light of his chart (the Sun) are in the 8th of his natal chart.

Using the Masha’allah-style of place combination, we might suggest that he has some intention to achieve a Saturnine standing in groups through death, fear, and destruction. I also think that Leo and the solar element both contribute meaning here, as does the bound of Mercury.

Hitler's Natal Chart
Hitler’s Natal Chart
Dahmer’s Twelfth-Part Ascendant

Looking at Jeffrey Dahmer’s chart, we find the twelfth-part of the Ascendant in the 8th of death. It is also in the bound of Saturn. It is conjunct Venus, the lord of the Ascendant, which is also the ruler of the twelfth-part. They are both in the same bound of Saturn in the 8th.  Therefore, the personal intentions and focus on Saturnine-Venusian, death, fear, and destruction themes are very pronounced.

Dahmer's Natal Chart
Dahmer’s Natal Chart

Explore Twelth-Parts

Start playing around with twelfth-parts in natal, horary, mundane, and electional charts. For electional astrology, putting the twelfth-part of the Moon in strong and good places is recommended by Sahl and others. Experiment, and if you have any revelations, feel free to share them in the comments.

Dorotheus of Sidon. (2005). Carmen Astrologicum. (D. Pingree, Trans.). Abingdon, MD: Astrology Center of America.
Manilius, M. (1977). Astronomica. (G. P. Goold, Trans.). Cambridge, MA: Loeb Classical Library.
Paulus Alexandrinus & Olympiodorus. (2001). Late Classical Astrology: Paulus Alexandrinus and Olypiodorus. (D. G. Greenbaum, Trans.). Reston, VA: Arhat.
Image Attribution
Featured image of Dodecahedron Aventicum (cropped) by Woudloper [CC BY-SA 3.0 (], from Wikimedia Commons


Blogger interested in all things astrological, especially Hellenistic, medieval, Uranian, and asteroid astrology.

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