Ehsan Khazeni – Methods of rectification in Persian astrology part 2

Part 2: Method of Vettius Valens:

In the pervious part, the rectification method of ptolemy was reviewed. That method is based on finding the Mubtaz or the most dignified planet on the time of previous new moon or full moon. In this part, I am going to introduce the method attributed to Vettius Valens.

Its good to know that his name is often written in form of Vaalis, Baalis or Faalis in Persian and Arabic texts. He was also called Valens of Alexandria, Valens of Qebt (Egypt) or Valens of Rome. He not only was considered as an astrologer but also as one of the greatest philosophers in Nizami’s poetries whose views were taken by Alexander the Great. “when Alexander the great wants to know the mysteries of creation, invited seven great philosophers who were Aristotle, Apollonius, Socrates, Plato, Valens, Porphyry and Hermes respectively”, Nizami writes.There are also stories in Persian texts around Sassanid kings corresponding with him regard unlocking the mysteries they faced which might not be true but proves that he had a great impact on that times.

As already mentioned in Previous part, I found this method in the book of Shahmardan which is belongs to 11th century but still it was existed in some earlier text such as the book entitled “An Introduction to Astrology” by Abunasr Qomi around 977BC. Abunasr was the court astrologer of Fakhr al-Dawla, a ruler of  Buyid dynasty who was successfully predicted his rise to power. his book is as valuable as Shahmardan’s work.

As time passes by, this method was eliminated from the books and as far as I know there is no example to show how to utilize it. The reason being might be its complicated literature. There is a treatise entitled “the Book of Valens” being held in National Library of Iran which doesn’t carry the mentioned method. I’ve checked the “Anthologiae" translated into English by Professor Mark Riley of Cambridge but still there is no sign of the method. The translator states that “The Anthologiae of Vettius Valens presents us with the longest, and at the same time the most difficult, text surviving from the astrological literature of antiquity” and I believe he is right! since the Persian translations are not easily readable and I should say that I could figure the technic out only after reading the text over 200 times! Anyways, the technic is not mentioned in the English translation as well.


This method is based on diurnal and nocturnal births. The Sun and the Moon as heavenly parents are two fundamentals in estimating the birth time. This method measures the distance between the Sun and the Moon and the elapsed time from sunrise to the birth time.

We know that the distance between the Sun and the Moon creates the lot of fortune and lot of spirit or unseen. so method tries to use the Arc of fortune_ as an indicator of birth.

Step 1:

The first step to calculate is called “Sun factor” that is the distance between the the Sun and the Moon at sunrise for diurnal births and at sunset for nocturnal births. 

Sun Factor = Moon – Sun 

If the number is less than zero, we should add 360.

 Example: In a diurnal birth we should measure this distance on sunrise. Suppose the Moon was in 26°45 Aquarius and the Sun was in 3°21Scorpio so the distance between is 113°24 which is 113.40 in decimal.

Step 2:

The second item we need is the estimated time of birth for which we should measure the exact distance from sunrise or sunset to this point. We measure the time between the sunrise to the given time for diurnal births and the time between the sunset to that time for nocturnal births to calculate the estimated time of birth.

In our example, the given time is 2pm and the sunrise was at 6:25am so the difference between these two is 7:35 minutes or 7.58 in decimal.

Step 3:

Now we should calculate another variable called the Ascendant factor. For that we multiply the above number attained in step 2 to the Sun factor.

Ascendant factor = Time from sunrise * Sun Factor

In our case we have:

113.4 * 7.58 = 859.57

Since the Ascendant factor is bigger than 360 we should take the reminder of its division by 360 which is 139.57°.

Step 4:

If the Ascendant factor is greater than the Sun factor, it means the birth time was before the given time and if it’s lesser then the birth time was after that time.

Now we calculate the ratio of difference. If the difference between two factors exceeds 180 the reminder of its division by 180 should be taken. The result should be multiplied by 4 and divided by 12. The final result is the minutes should be added or deducted from the given time.

In our example the Ascendant factor is bigger than the sun factor which means the time of birth was a few minutes earlier.

((139.57-113.4) *4) /12 = 8.7

8.7 is in decimal and should be converted in time format which is 8:43 minutes. If 8 minutes and 43 seconds subtracted from 2pm, the rectified time is 1:51:17 pm please note that I used the data in minutes but by using seconds and also considering the seconds of the sunrise for more accuracy, the result will change by ±30 seconds.


The reason of multiplying the number by 4 and dividing by 12 and not dividing by 3 from the beginning is not known to me. I could be the diurnal and nocturnal arc which is 12 hours and equal to 180 degrees from ascendant to descendent.

One of the weakness points of this system is that if the estimated time after the sunrise is exactly one hour, the same time will always be verified because the distance between the Moon and the Sun won’t matter since the Sun factor and the ascendant factor will be equal.

Regarding the fact that the method correlates to the given time and whatever time is given will be added to the equation, if the given time is a span of time then the beginning and the ending of the span will return two different rectified time which might not necessarily fall into that given span. So it seems this equation is only to alter few minutes and seconds for those horoscopes which already have almost accurate birth time.