An Error in Junctinus’ methodology on Solar Returns?

Junctinus was an Italian astrologer, medical doctor, theologian, mathematician and the author of the influential 16th century astrological text Speculum Astrologiae (1583) which contained the data and charts of the figures of his day, including his own birth chart. Lacking a modern computer, Junctinus calculated his charts by hand and made some errors in calculation in various charts. Nonetheless, he was highly regarded as an astrologer and was employed as a teacher of Catherine de Medici.

AstroDatabank gives the following as his birth details:

NameJunctinus Gender: M
BirthnameGiuntini, Franciscus
born on8 March 1522 Jul.Cal. (18 Mar 1522 greg.) at 01:20 (= 01:20 AM )
PlaceFlorence, Italy43n46, 11e15
TimezoneLMT m11e15 (is local mean time)
Franciscus Giuntini (1522 – 1590?) also wrote a text in Latin about Solar Revolutions in the year M.D. LXX (1570)

Francisci Ivnctini florentini S. T. Doctoris also published the following book in the year 1570 on Annual Revolutions and Solar Returns:

Tractatus iudicandi reuolutiones natiuitatum : omnia, quae pertractantur in hoc libro non solum astrologis, sed etiam vniuersis bonarum artium studiosis vtilia, [et] iucunda, atque aliter explicata, quam hactenus fuerint ab aliis tradita : vit sapiens dominabitur astris.

(A treatise for judging the revolutions of births: all things which are handled in this book not only for astrologers, but also for all students of good arts, useful, [and] pleasant, and explained in a different way, than they have hitherto been rendered by others. The wise man will rule over the stars.)

I recently obtained a copy of Junctinus’ 16th century Latin text and began reading some key passages. I was particularly interested in his method of distributing the influence of the annual revolution over the days of the solar return year, which he took almost verbatim from the writings of the 4th century Roman astrologer Julius Firmicus Maternus. For his part, Firmicus Maternus derived the method from the 2nd century Hellenistic astrologer Vettius Valens, who appears to be the original source of the technique. Unfortunately, along the way various errors crept into the transcriptions of the original text of Vettius Valens, and these ended up in the solar revolutions book by Junctinus in the 16th century. Specifically, I am referring to the following chapter from pages 146 and 147 of Junctinus’ Latin text:

Junctinus’ table of the number of days assigned to each planet in the solar revolutions contains several errors, as explained in the remainder of this blog. Junctinus appears to be unaware of the fact that the values assigned to the planets are based on the ancient theory of the minor (small, least) years of the planets, described in the texts of Hellenistic astrologers.

Here is my loose translation of the above Latin text:


Distribution of the year by days.

The days of the entire year are also divided among the individual planets, from which arise ailments, weaknesses, gains, losses, pains, and joys: for when benevolent stars [planets] receive the day, we are freed from all evil. But when [the planet is] malevolent, sudden misfortunes befall us. The host, therefore, or the master of the sign to which it was handed over by the forward movement from the horoscope, claims for himself the first days: and after him, the other planets, as they are individually placed in the figure of the birthday [natal chart], says Firmicus in ch.19. lib.2.

But, in my opinion, we must take the distribution of the year from the lord of the year [domino anni, that is, the ruler of the profected ascendant of the year], after which we divide the year among the other planets, as they are individually placed in the chart of the annual rotation, according to the sequence of signs. In this space of days, we can find all the things that are coming to us: having thoroughly examined beforehand the location and quality of the signs, for if the star [planet], which will govern those days of our birth, is well placed and benevolent, it determines all good things. The number of days which each planet is allotted is as follows:

Days: Saturn – 85, Jupiter – 30, Mars – 36, Sun – 53, Venus – 33, Mercury – 57, Moon – 71.

Junctinus makes clear that he is deriving his method of dividing the solar return year into seven periods, each ruled by a particular planet in the order in which they appear in the solar return chart. He disagrees with Firmicus about which planet initiates the sequence. Firmiucus begins dividing the solar return year into periods of days, beginning with the ruler of the solar return Ascendant. Junctinus disagrees and states that, in his opinion, it is preferable to begin the sequence with the Lord of the Year, that is, the ruler of the annual profected Ascendant. The other planets are then arranged in the sequence in which they appear in the solar revolution, beginning with the Lord of the Year. Each planet is allotted a certain number of days, as indicated in the list provided by Junctinus, the total of which adds up to 365, the number of whole days in a year. [After re-reading the Latin text and pondering the words of Junctinus, I have changed my mind about the above paragraph and modified my understanding of his approach — see Addendum #3 at the end of this post. — 11 April 2022]

Junctinus appears to have been unaware that Firmicus derived the number of days assigned to each planet from the work of Vettius Valens in the 2nd century. Valens writes (Mark Riley translation):

Vettius Valens, Anthologies, Book IV 71 /158K;150P/

The Anthologies of Vettius Valens of Antioch: Book IV

1. The Distributions of Periods.
We believe that we have set forth an appropriate, in fact, magisterial, explanation of the previous . We will now reveal a topic investigated by many and hidden from view, namely the distribution of propitious and impropitious times. We must preface our discussion with the distributions which have been proven by our own experience. The primary period is one-fourth of the minimum period, as follows:

Star…………………………Period ……………………. One-fourth Period ……………………….. Days/Year

Saturn……………………..30 ………………………….. 7 1/2 ………………………………………….. 85 Jupiter……………………..12 ………………………….. 3 ……………………………………………… 34
Mars ……………………….15 ………………………….. 3 years 9 months………………………… 42 1/2
Venus …………………….. 8 …………………………… 2………………………………………………… 22 2/3 Mercury…………………..20 ………………………….. 5………………………………………………… 56 2/3
Sun …………………………19 ………………………….. 4 years 9 months………………………… 53 5/6 Moon………………………25 ………………………….. 6 years 3 months………………………… 70 5/6

Altogether, the “fourths” total 32 years 3 months.

Let’s compare Valens’ original text with the 16th century rendering by Junctinus, and the errors will become apparent.

2nd century
Valens rounded (up or down)Firmicus Maternus
4th century
16th century
Jupiter34343030error in Maternus & Junctinus
Mars42 1/2424236error in Junctinus
Sun53 5/6535353
Venus22 2/3232333error in Junctinus
Mercury56 2/3575757
Moon70 5/6717171
TOTAL days per year365.5 days365 days361 days ??365 days

The values given by Valens agree with his method of calculation and can be assumed to be a correct rendering of the original method. The errors introduced by Firmicus (Jupiter as 30 instead of 34) and Junctinus (errors in Jupiter, Mars and Venus) are most likely due to copyist errors in transcribing original texts.

My suggestion to practicing astrologers, who use this method of distributing the solar return over the seven visible planets in the course of the revolution year, is to return to the assignment of days as originally proposed and mathematically calculated by Vettius Valens. Here is how Valens calculated the number of days for each planet based on the classical ‘small periods’ of the planets, which were rooted in the recurrence cycles of the planets, that is, cycles at the end of which the planets conjoin the Sun in approximately the same degree of the zodiac. Again from Mark Riley’s translation:

To Find the Days of Each Star.

The days of each star are found in this way: double the star’s period, then take one-half, then one-third of the period. After adding all these figures together, we will find the days. The period of Saturn is 30 days; I double this for a total of 60. One-half of 30 is 15; I add this to 60 for a total of 75. One-third of 30 is 10; I add this to the 75 for a grand total of 85. Saturn will have this number of days. Likewise for the rest of the stars.

My guess is that Valens came up with his formula as follows. He knew that the sum total of the minor years of the visible planets was 129, and he wanted to project 129 onto the length of the year, which he knew was slightly more than 365 days: 129 –> 365. He must have toyed with some arithmetic and realized that 2 x 129 = 258, 1/2 of 129 = 64.5, and 1/3 of 129 = 43, so if you add together 258 + 64.5 + 43, you get 365.5 days, which is very close to the known length of the tropical year.

To illustrate the error regarding Jupiter in the texts of Maternus and Junctinus, we use Valens formula and double Jupiter’s base period (its classical ‘small period‘ — see the table from Arhat Media below), then add one-half of the base period and then one-third of the base period. Jupiter’s base period is given as 12, which is doubled to 24 (2 x 12). Half of the period is 6 (12 divided by 2) and a third of the period is 4 (12 divided by 3). Thus, we must add 24 + 6 + 4 and arrive at 34 as the number of days of the year assigned to Jupiter in Valens’ formula. Hence the value of 30 given by Firmicus and Junctinus are obviously in error and probably represent typographical or copyist errors in transcription.

The following table of the classical small (minor, lesser), mean and great periods of the planets is quoted from Arhat Media:


The small periods are derived from recurrence cycles, cycles at the end of which the planets conjoin the Sun in approximately the same degree of the zodiac. 

Bruce Scofield explains the small or minor years of the planets as follows:

Every eight Sun years turns out to be the same as five Venus years. Every 19 Sun years the Moon and Sun meet at the same place. This is called the Metonic Cycle. Every 12 years Jupiter passes through the entire ecliptic and returns to the same place. Saturn does this in about 30 years. These astronomical facts were not lost on ancient calendar and ephemeris makers. In fact, in ancient Western astrology each of the planets has a set of specific years, a list that appears in many ancient texts. Here’s the list:

The Least or Minor Years of the Planets: 

Sun – 19 (Metonic Cycle)
Moon – 25 (309 lunation cycles in 25 Egyptian years of 365 days)
Mercury – 20 (63 synodic cycles in 20 Egyptian years)
Venus – 8 (5 synodic cycles of Venus equals 8 solar years)
Mars – 15 (7 synodic cycles in 15 Egyptian)
Jupiter – 12 (11 synodic cycles in 12 Egyptian years)
Saturn – 30 (29 synodic cycles in 30 Egyptian years


If we add up the minor (small, least) years of the seven visible planets, we get the sum total of 129 years. Valens sought to project this sum onto the total number of days in a year (365.24 in a tropical year). Valens chose the arithmetic method of adding together twice the period, half the period and a third of the period. A simpler method would have been to multiply each minor period by the ratio of 365 days in a year to 129 total days in the minor periods of the seven planets:

365.24 days in a year divided by 129 total minor days = 2.83 annual days per each minor year day. Doing the math:

Saturn: 30 x 2.83 = 84.9, rounded to 85.
Jupiter: 12 x 2.83 = 33.96, rounded to 34.
Mars: 15 x 2.83 = 42.45, rounded to 42.
Sun: 19 x 2.83 = 53.77, rounded to 54. (Valens rounded this down to 53.)
Venus: 8 x 2.83 = 22.64, rounded to 23.
Mercury: 20 x 2.83 = 56.6, rounded to 57.
Moon: 25 x 2.83 = 70.75, rounded to 71.

Today with the availability of home computers, it would be simple to use the precise values, accurate to two decimal points, rather than the rounded values to calculate favorable and adverse periods during a solar return year, if one were so inclined.

The choice of whether to begin the distribution with the ruler of the Solar Return ascendant, as Firmicus recommends, or with the Profected Lord of the Year, as Junctinus advises, is worth further experimentation to evaluate which technique gives better results in practice.

Addendum: In researching this matter a bit more, I found that Alexandre Volguine in Chapter 14 of his classic text on the technique of solar returns, first published in France in 1937, discusses the seven planetary periods and quotes Junctinus’ table, repeating the errors in the periods of Jupiter, Mars and Venus. He correctly attributes the source of this method of dividing the year to Firmicus Maternus but adds that he is unaware of how the planetary periods listed by Junctinus were derived.

Volguine writes, in the 3rd edition of his book, that he learned about and tested Junctinus’ method during a period of 10 years, and found that there is a “good deal of truth” in it, provided that you start from the planet ruling the solar return ascendant (not the Lord of the Year, as Junctinus recommends) and continue in the Chaldean order of slowest to fastest planet (Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon), which is contrary to what both Firmicus Maternus and Junctinus recommend. Perhaps if Volguine were working with the correct planetary periods as calculated by Valens, he would have found the technique to be even more reliable.

Addendum #2 (10 April 2022):

Reading over Junctinus and Maternus, I suspect that Junctinus either misunderstood or re-interpreted Firmicus Matenrus’s comments about the division of the year among the seven visible planets when he applied it to solar revolutions.

Quoting from Holden’s translation of Maternus, Chapter 28 on the Division of Times, “the year … takes its beginning from the Asc, and the first year will be the sign in which the Asc is placed, the second in the second sign, the third in the third sign, and thus the others in order.”

Clearly Maternus is talking about annual profections and not about solar revolutions in this section. Most likely Valens also had the annually profected chart in mind. Maternus then goes on to discuss “the division of the year” in Chapter 29, which is the text which Junctinus translates and incorporates into his own book on solar returns.

According to Holden, Maternus writes: “in whatever sign the beginning of the year is, the ruler of that sign receives the first days, and after him the others, according as they are severally placed.” Maternus appears to be continuing his discussion of annual profections.

Junctinus may have assumed that Maternus was referring to the solar return ascendant, but in the previous section Maternus clearly related the beginning of the year to the profected annual ascendant, so it appears that Junctinus either misunderstood Maternus or else he may have been creatively applying the method of Maternus, regarding profections, to solar returns charts, which was the topic of his own book.

If I am understanding these ancient texts correctly, then Junctinus used the ideas of Valens and Maternus regarding annually profected charts to distribute the solar revolution year into periods of days,ruled by the 7 visible planets as chronocrators or time-lords, beginning with the Lord of the Year (ruler of the profected ascendant) and then in the sequence of the planets as they appear in the solar return, that is, “according as they are severally placed.”

Junctinus appears to have been discussing solar return charts because his book is about annual revolutions, and he wrote regarding the 7 planets, “prout sunt singuli in annuae conversionis schemate collocati secundum signorum consecuentia” — “as they are individually placed in the annual rotation chart, according to the sequence of signs.”

Addendum #3 (11 April 2022):

After further reflection on Junctinus’ Latin text about the distribution of the days of the year among the 7 visible planets, I believe that I may not have correctly expressed his method above, and I apologize for any confusion I may have caused. Junctinus makes the following points:

  1. According to Firmicus Maternus, the Lord of the Year (the planet that rules the profected ascendant) governs the first period of days in the division of the year.
  2. The remaining six planets then receive rulership of the remaining six periods of days, as they are individually placed in the figure of the birthday [natal chart].
  3. Junctinus is of a different opinion, namely, that we begin the distribution of the days of the year from the Lord of the Year BUT we divide the remainder of the year among the other six planets, as they are individually placed in the chart of the annual rotation, according to the sequence of signs. (I initially thought he was objecting to the planet from which to begin the distribution. On further reflection, I believe he was objecting to using the positions of the planets in the birth chart as opposed to the “annual rotation” chart.
  4. Hence, if I understand Junctinus correctly, he begins the distribution of the days of the year from the Lord of the profected Ascendant, but he distributes the remainder of the days of the year to the remaining planets in the zodiacal order in which they appear in the solar return, after the position of the Lord of the Year.

All original material in this blog is copyright Anthony Louis 2022.

About Anthony Louis

Author of books about astrology and tarot, including TAROT PLAIN AND SIMPLE, HORARY ASTROLOGY, and THE ART OF FORECASTING WITH SOLAR RETURNS.
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3 Responses to An Error in Junctinus’ methodology on Solar Returns?

  1. Peter Orne says:

    Hi Tony, I think you will enjoy this: Peter

    Sent from my iPhone


  2. Pingback: ¿Un error en la metodología de Junctinus sobre los retornos solares? - Academia Astrologia Avanzada MB

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