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

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)

What are the Twelfth-Parts?

The twelfth-parts, also known as dodecatemory/dodekatemoria or duodena/duodecimae (or dwad, short for dwadashama, in Indian astrology), appear in the earliest strains of Hellenistic astrology.  As the 1st Century CE astrologer, Manilius, explained in the quote above, the twelfth-parts are divisions of each astrological sign into 12 equal parts, each one assigned a zodiacal sign beginning with the greater sign itself.  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 that precedes the sign it’s in.  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.  For greater accuracy, the second method is used, in which we take the degrees and minutes of the position within the sign and multiply 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.

The FREE, open-source, traditional astrology program, Morinus, is soon to have twelfth-part calculation built-in.  Some of the developers of the program have been very kind to me and have given me the chance to check out this functionality.  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.

There are two other quick notes about calculation.  First, 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.  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, and I don’t use these subdivisions myself in practice.

Secondly, Paulus Alexandrinus (4th Century CE) gives an idiosyncratic variety of twelfth-parts, which seems most likely to be 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, and it seems to suggest that he feels a need to justify why he is doing things against the norm in his work, giving recognition to the fact that multiplication by 12 is the typical (and logical) approach to the twelfth-parts.  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, but this is hardly a noteworthy argument, as the first 2.5° of the sign already fall to that same sign in the standard system. 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, then explain the idiosyncratic Paulean form. As far as I know, this idiosyncratic form of twelfth-part is both an innovation of Paulus (which he appeared rather proud of) and 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)

Who Used the Twelfth-Parts?

In addition to Manilius, the twelfth-parts discussed (i.e. the one in the method of Manilius, not of Paulus) were also used by almost every Hellenistic astrologer, including 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, Vettius Valens (2nd Century CE) in multiple sections of his Anthology, Julius Firmicus Maternus (4th Century CE) in Book II, Ch. 17, and many other sections of his Mathesis, Porphyry of Tyre (3rd Century CE) in Ch. 39 of his Introduction to the Tetrabiblos, Hephaistio of Thebes (5th Century CE) in Book I, Ch. 18 (definitely not explained like the method of Paulus but erroneously identified as such by Rob Hand in the footnotes of the Project Hindsight edition) and in Book III of his Apotelesmatics,  and Rhetorius in Ch. 18 of his Compendium.  The twelfth-parts were also a basic component of astrological technique as practiced by later Persian-Arabic astrologers of the early medieval period (and beyond), including Sahl, Masha’allah, Abu Ma’shar, al-Qabisi, and Abraham Ibn Ezra.

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.

How were Twelfth-Parts Used?

The twelfth-parts produce a secondary zodiacal position for each planet and point in the chart, as if each point is projected into an additional hidden zodiacal position.  There are four main senses in which the twelfth-parts are used: 1. Twelfth-part of the Moon gives indications regarding the physical sex of the person, 2. Twelfth-part of the Sun gives indications about Ascendant when it is unknown, 3. Twelfth-part of the Ascendant reveals thoughts/intentions, and 3. Twelfth-part positions give 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 I find the last use to be the most fruitful.

Sex of a Person from the Natal Chart

Both Dorotheus (Book I, Ch. 8 of Carmen) and Valens (Book IX, Ch. 8 of Anthology) use the sex of the sign of the twelfth-part of the Moon as having bearing on the sex of the native.  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, including: 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.

Putting this method to the test we find that it works poorly 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

However, one might argue that perhaps Dorotheus was wrong, and the twelfth-part of the Moon should be given the primary consideration in this endeavor, without it being easily over-ridden by other factors.  So, let’s turn to the chart of Traci Lords.  Her Ascendant is in a masculine sign but Sun and Moon in feminine signs, while the twelfth-part of the Moon is in a masculine sign, and its ruler, Saturn, is also in a masculine sign.

Traci Lords' Natal Chart
Traci Lords’ Natal Chart

In conclusion, we cannot rely upon the twelfth-part of the Moon methods as set forth by 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 (particularly those of body relevant points such as the Moon, Fortune, and the Ascendant), but so far we don’t have such a technique.

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 but one method of rectification among many explored and elucidated by Valens.  The method, and I may be getting parts of it wrong, appears to involve 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. After finding the twelfth-part of the Sun’s position, the Ascendant for a day birth will either be the sign opposite that sign, 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) – but 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, but 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, and still doesn’t give you an accurate indication is not a very valuable technique, so I won’t explore it further.

Interpretation of Cognition

One of the more fascinating niche uses of twelfth-parts is in the interpretation of cognition, particularly in consultation and horary charts.  This use appears to originate with unknown Indian astrologers and Hephastio of Thebes, and really starts to take off with 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, pertaining to the house of the chart, and the qualities and conditions of that place such as the quality of the sign, its domicile lord, and occupants of the sign.

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, as he not only explores it in his introduction, translates a work which uses the technique, and provides commentary, but he also includes appendices with further discussion and translations, including the entire 144 significations of each twelfth-part of the Ascendant given by Hephastio in tabular form.

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

Masha’allah in On Hidden Things (see Works of Sahl and Masha’allah translated by Dykes in 2008) suggested that among a number of methods he names, the best method for finding the significator of a querent’s intention in an horary reading is to look at the twelfth-part of the Ascendant.  If a planet is in that place then you look to that place as signifying the person’s intention, whereas if the place is empty then you look to the place of its ruler.  In an example that Masha’allah gave (the exact same example was also 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, the 5th place from the Ascendant.  Leo was empty in the horary chart and the Sun was in Libra, the 7th, so Masha’allah surmised that the question involved the 5th in the condition of or seeking the 7th, i.e. 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, and that 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.

Use in Natal Charts

Used with natal charts the technique puts an interesting twist on the idea of personal focus and fulfillment, or even “primary motivation”.  The ruler of the Ascendant shows a particular pull towards a certain place in the natal chart and 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 post on twelfth-parts, I’ll explore their use in natal delineation in more depth, drawing heavily on Maternus, who found in twelfth-parts the secret to more accurate delineation.  However, even just looking at the twelfth-part of the Ascendant in natal astrology, we can find some interesting things.

Hitler had the twelfth-part of the Ascendant with the greater malefic Saturn, in the bound of Mercury, in the networking and popularity-oriented 11th House (house of friends), in the sign of leadership, Leo, while 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, though I 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

Looking at Jeffrey Dahmer’s chart we find the twelfth-part of the Ascendant in the 8th of death in the bound of Saturn, conjunct the lord of the Ascendant, which is also the ruler of the twelfth-part, in the exact 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

Start playing around with twelfth-parts in natal, horary, and electional charts (putting the twelfth-part of the Moon in strong and good places is best for elections and 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.

23 thoughts on “Twelfth-Parts | 1. Introducing the Dodecatemory of the Signs”

  1. This whole thing about the 13 – I really don’t know. I used to believe it was a mistake in the way later authors interpreted old explanations of modulo arithmetic, but these days I think it was taken from the way that Ptolemy re-interpreted the theory of Profection, so that the Months would match the years at the beginning of the next year, instead of having to Jump over to get to the next sign. I believe this method was adapted to reinforce the idea that time is a continuous flow, rather than a cycle of discreet “portions” – which may be the reason that older methods of direction, such as Aphesis, were abandoned, and primary directions came to be understood as a linear series of “hits” or “events” rather than “time periods” in which one planet hands over its substance/form operations to another. I think this older doctrine of time being composed of separate and discreet entities works better for me in practice, and is the reason why we (those of us who are of a traditional bent) consider the signs as separate entities –

  2. Thank you Anthony for sharing your knowledge. I have come to make use of dodecatemoria as a natural “fractal” of Manilius Decans, which are, in my opinion the most accurate and natural sub-division, and the one that provides me with most sound psychological insight on a planetary or angle position on a chart.

    Manilius did not elaborate the subdivisions of duads in five parts, which led me to think of a manner to deal with this enigma.

    What I do, is relocate zodiacal signs, not planetary rulerships, ocupying each 1/2 degree, but in a subsequent order defined by the sequentials arising from the aplication of the “quincunx dynamics” beggining with Aries.
    So the sequence, on every sign, follows the pattern Aries-Virgo-Aquarius-Cancer-Sagitarius-Taurus-Libra-Piscis-Leo-Capricorn-Gemini-Scorpio…Aries. And so again and again.

    I found the geometrics springing from this excercise, absolutely fascinating, and very much reminiscent of life unfolding at biological levels.

    Every decan contains thus 20 of theese subdivisions, which have a set of 4 nuclear signs that appear only once in the decan, with two pairs of “mirror sequences” on each end of the decan nuclei which twice repeats each of the remainig 8 signs.
    Thus each one of theese “mirror sequences” made of 10 signs share 8 identical features but 2, which are the nuclei 4 signs splitting apart and assigning exclusive qualities to each half of the decan.

    When I first came across this, I could not avoid thinking of celular and DNA behaviour.

    I have so far not moved any further within this path, being cautious.
    In any case, working with zodiacal sub-divisions is a fascinating field and it is a pleasure to read your very thorough and sound observations on the matter.

    Kindest regards,

    Juan de la Fuente.

  3. Hello again,
    Taking for example the Libra sign. Its third decan is Sagitarius. And within that decan we find Gemini-Cancer-Leo-Virgo dodecatemoria.

    Taking Gemini into consideration, the “core undertone or pulse” is youthfull adaptability, which moving into the meaning of Sagitarius decan, expresses itself as ilusions and expectations. As the outermost expression is Libra, dependency on others is the field where, say, the Sun would center the individuals attention.

    In the case of Cancer, the second dodecatemoria, the will to become, or identify with the “idealised image” of oneself in the other one´s eyes,(Sag-Libra) is conditioned by a core desire to root, breed and belong (Cancer)

    Thus decans and dodecatemorias combine to offer a much more detailed portrait of the internal thought and feeling process that shape personality.

    I will carefully study the methods and criterea you propose in your articles, I am sure they will be very enriching.

    Greetings from Spain,

    Juan de la Fuente

  4. Hello Anthony!

    I am very glad to find some friendly pages about Hellenistic Astrology. And with an author so concerned with comprehension of his public. Your articles are very clear and easy to get.

    Neverthless, I am a bit troubled with some “house division” in some of the charts here: For exemple, Hitler. When you say that his Ascendant’s twelfth-part is with Saturn, ok – They are on the same sign. Same thing when you say that it is in the bound of Mercury – easy to see in the chart.

    But how the Ascendant’s twefth is in the eleventh house, being so far from the eleventh’s cusp, still on the 10th house and in 10th sign ? Same thing for the Sun’s twelfth, still in the seventh, but considered as it was in 8th ? On Sun’s twelfth, I can see that it was in the 8th sign, ok – but what I can see regarding the AScendant’s twelfth ?

    So, I really don’t get it – what I am missing here ?

    Thanks for you attention!

    1. Hi Livio,

      The signs are the houses of the planets. For instance, if Libra is rising, then Libra is the first house, the diurnal house of Venus. The next sign that rises, Scorpio, the nocturnal house of Mars, is the second house, and so on. There was some experimentation with spatial houses, mainly for strength/prominence considerations, late in the Hellenistic era but these whole sign houses are the original houses for topics and the same way houses are still typically done in Indian astrology. It is the same with Lots for topics. The Lot itself is a focal point for the topic but the topic is also inferred for the entire sign/house that the Lot occupies. Similarly, planets in the same sign were in a very strong relationship together, even if on other ends of the sign, called being “with” each other or “co-present”, but especially if within 15 degrees and applying, in which case they were “in assembly”, and even more so when within 3 degrees, called “in adherence” or adhering to each other.

      Best wishes,


  5. Thanks, Anthony!

    Since I am getting started with the Morinus configurations, I’ve jost seen what I have missed after I’ve configured it to the whlole houses system – I was thinking about MC as the starting point for the whole 10th house, not just a point

    So, the next sign is rightly the eleventh house. Get it!

    Thanks !

  6. I have two other questions:
    1- I have casting the map for Hitler, but after the birthtime, the initials ZN has appeared, instead the LC letters in the chart of this article – what they mean ?
    2- When working with twelfth-parts from the angles (Asc, MC), even AA charts, may not give us the level of accuracy of the birthtime needed – if they change signs every 2 and half degrees, 10 minutes difference between the birthtime and the time that “someone” has written on a paper(for example, from 10:12 to ten o’clock), we can change completely all the meaning we can get for these points! How can we deal with that level of uncertainty ?

    1. Hi Livio,

      Yes, there may be some problems with my relying on AstroDatabank for that chart and even with their AA rating on that. Typically with an AA chart, it won’t be off by more than about 5 minutes, but even then the twelfth-part of an angle can certainly be problematic. In this case, your chart may be off by a degree by not using Local Mean Time (LC) rather than Zone (ZN) timing.

      Best wishes,


  7. Hello Anthony,
    There is a wise man who lived in Brazil, called josé gabriel da costa, born precisely at noon on feb. 10th 1922 at feira de Santana Bahia, a man his folowers believe to be god sent.
    I tried around the 12th part method on his chart and WOW! 12th part of ASC conjunct 12th part north node conjunct natal sun on 10th, and the sun’s 12th part conjunct the 12th part of the lord of the ASC conjunct natal North node on the 6th (10th from the 9th)
    Sun rules 4th house of origin.
    Part of Faith conjunct IC ruled by the sun.
    I dont know what a configuration for someone being god sent would look like but this does seem to fit the bill!
    Amazing stuff!
    Thanks alot once again

  8. Dear Lucas,

    The only point that is good to check, before deriving to twelfth parts, is to check, if this is the real time that one is born, since “noon” is the time that usually is chosen, when people don’t know the real moment of the birth.

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