There are many arguments against astrology that are age old. Firmicus Maternus, a 4th century CE Roman astrologer from Sicily begins his Mathesis by dealing with such arguments and among these is the issue of twins; how come twins, which are sometimes born just a few minutes apart have different lives, yet their horoscopes are virtually identical.

Unless we use a very small subdivision of a zodiac to gain more precise insight we won’t be able to see the differences between two horoscopes with only a few minutes of difference.  In Vedic astrology many astrologers today use shashtiamsha (a division of a sign into 60 half a degree parts) while a less known method which I don’t see practiced today and seems to be very rare was to use what is called prana dwadashamsha (first dividing a sign into twelve 2 and a half degree parts and then further divide these into 12 parts). In the west however most astrologers are not aware that such extreme fine tuning tools were available in traditional Hellenistic and medieval Persian traditions, too, albeit with a difference.

Firmicus Maternus in his Mathesis stresses the importance of looking the position of a 12th part of a planet or point in the unequal sized division called terms or bounds. This roughly brings us to a similarly microscopic division such as the Indian shastiamsha. Let’s look at the technicalities:

The below figures are expressed in an idealized manner, thus they are approximations.

1 sign rises about 2 hours (depending on the rising time of the sign in question)

15 degrees of a sign rise about 1 hour.

1 degree rises about 4 minutes.

The ascendant changes a 12th part in about 10 minutes (one 12th part is 2 degrees, 30 minutes).

A 12th part of the ascendant changes a bound in about 2 minutes (if we idealize the bounds and make them 5 degrees each).

To get more familiar with the 12th parts, please, see my article.

When it comes to twins, all of the planets will have the same placements except for the Moon if the births are sufficiently apart, but if we’re talking only a few minutes, only the four angular cusps will move a bit (and if one uses a quadrant house system all of the house cusps will change) and the 12th parts of the Ascendant and Midheaven will change the bounds and in some cases signs.

Below is just a chart of one moment which I’ve created for the purpose of illustrating how the bounds placement of 12th parts change within a few minutes.  Pay attention to A (12th part of the ascendant) and M (12th part of the Midheaven) on the outside of the wheel.

 Picture no. 1: 12th parts changing bounds

The 12th part of the Ascendant in Jupiter’s bound comes to Venus’ bound after 1 minute.  After 3 minutes it is still in the same bound, but after 4 minutes it would already be in Saturn’s bound. In between, after about 2 minutes it is conjunct by exact degree radix Saturn and South Node.  This is certainly something worth paying attention to if this was a birth time rectification.

The 12th part of the Midheaven in Saturn’s bound has come to Mercury’s bound after 1 minute and then to Mars’ bound after 3 minutes.

Note that one zodiacal sign for 12th parts is not 30 degrees but 2 and a half degrees. We are simply superimposing the micro zodiac onto the root zodiac – twelve 30 degree zodiacs onto the original 360 degree zodiac.

Such fine precision could be very useful in multiple question horary sessions, where the focus could be on the 12th parts. We know the 12th part of the Ascendant is important in horary as it shows the real concern of the querent, but I see no reason why the 12th parts couldn’t be utilized more.



Recently I gave a reading to twins, male and female, born only 9 minutes apart.  Of course, they live different lives and their bodies are very different.

The main and obvious differences are:


Darker, brown complexion

Thin, but not overly so

Gentle and feminine

Artist (academic sculpturer / designer)


Bright, white complexion

Strong, round, fatty body

A bit more masculine                                                    

Social / youth worker

Picture no. 2: Male twin with 12th parts outside the wheel

In the chart of the male twin the Ascendant is in the bounds of Venus, thus we have a feminine nature expressed twice, first through the sign of Cancer, then through the bounds of Venus.  This also speaks about him being an artistic person and Venus gives him a darker, brown complexion and a nicely built body.

The 12th part of the Ascendant falls in Virgo, 3rd house in the bounds of Saturn. Precise and skillful Virgo, mutable earth and Saturn. Changing one earth form into another by sculpting.

The Midheaven falls in the bounds of Venus as well. Venus has the most rulership over the Midheaven by being the exaltation ruler, a triplicity ruler and the bound ruler of the Midheaven. She is exalted in the 11th house of hopes, wishes, success and gain. He excels in his work without a doubt and has high hopes.

The 12th part of the Midheaven falls in 12th house,Gemini, bounds of Saturn. Hand skills, craft, art and Saturn, stone. However, it is in the 12th house and it is interesting that although this is what he studied for his income he is doing art projects that do not involve sculpting, but instead he is designing luxury silk shawls – Venus (beauty, silk, luxury, feminine) in Taurus (beautiful forms, neck) in the 11th house of gain / profit.

Picture no. 3: Female twin with 12th parts outside the wheel

In the chart of the female twin the Ascendant has moved to the bounds of Jupiter which makes her body fatty and her complexion more bright, white. Also, the 12th part of the Moon, the ascendant ruler and the natural significator of the body is conjunct the 12th part of Jupiter, which further enhances the roundness of the body. She also likes travel and she is a manager of international youth exchanges. She is also a cellist and a violinist.

The 12th part of the Ascendant falls in the 9th house, Pisces, bounds of Mercury and conjuncts the 12th part of Saturn. This further enhances her work with foreign countries and travel and bounds of Mercury again signifies management. She also has a more serious nature as her twin brother due to Mercury-Saturn conjunction by 12th parts. Her ascendant get some male quality two times; first it falls in Jupiter’s bound, and the 12th part of the Ascendant is conjunct Saturn. Since we are quite dependant on these fine tuning tools, this is what suggests she expresses also quite a bit of masculine energy.  According to some, Saturn is female in the guise of a male, which I find very interesting especially in both cases.

The Midheaven falls in the bounds of Saturn and Mercury is tightly on it, in Pisces, 9th house. The theme of travel and education is again present, but here we have long distance correspondence and management. We shouldn’t neglect the fact that Mercury has to do with youths, either.

The 12th part of the Midheaven falls in Aquarius, 8th house, bounds of Jupiter.  This might give us additional confirmation about her being involved in social work.

Both of them have the 12th part of the Midheaven in malefic houses and both of them have a difficulty in making their careers visible and successful.  



They have both studied a musical instrument (Moon in the 1st in her own Sign, Venus in Taurus in the 11th, sextile to Moon, 5th ruler Mars in opposition to the Moon). Venus also aspects the 5th house by opposition and the 5th ruler by trine.

They both have difficulty in relationships (7th ruler in the 6th and Mars in the 7th).



I hope I have managed to illustrate the importance of the 12th parts and their bounds positions in situations where such a microscopic analysis is necessary. I have partially set out to write about this, because there is a general belief that only Vedic astrology possesses such fine tuning tools and that when it comes to twins, astrology developed west of India can’t offer anything substantial. It is true that today the 12th parts are under-utilized and their placement in the bounds is even more so. I am hoping for more research and some good exchanges in this field in the future.

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