BogdanKr wrote:[...] but beeing the one bearing meanings for the astrologer, may be that for some house systems thsese two books are full of writings on them.

Oh, undoubtedly. But we were discussing what meaning they had to Ptolemy, who wrote them. As the Almagest shows, he clearly had the mathematical tools to devise most or all of the quadrant systems we know today. And yet, as the Tetrabiblos shows, he didn't. 'Mikes you fink, don' it?'

the simple fact is that there is no mention (that I have been able to find, at least) of house division in the Almagest, and almost none in the Tetrabiblos. There isn't much to interpret, other than silence.

Oh, undoubtedly. But we were discussing what meaning they had to Ptolemy, who wrote them. As the Almagest shows, he clearly had the mathematical tools to devise most or all of the quadrant systems we know today. And yet, as the Tetrabiblos shows, he didn't. 'Mikes you fink, don' it?

As Gjiada has already suggested not everyone who has studied Ptolemy would accept your conclusion that that he makes no reference that could be construed as indicating his use of houses. However, I agree with you that it remains ambiguous what system of house division Ptolemy was actually using.

To assist our discussion here is a selection from 'The Houses: Temples of the Sky' by Deborah Houlding. I hope Deb doesn't object to this being put up here. It seems very relevant to this discussion. While not disputing that Ptolemy largely ignores the issue of house division she does point out one section of the Tetrabiblos that may imply a system of house division used by Ptolemy.

Clearly Ptolemy regarded the houses with some irrelevance but the question of which method of house construction he was referring to has still managed to provoke great debate. His constant overlapping of the words 'place' and 'sign', and the way in which he refers to the midheaven as 'the culminating sign' has been used to suggest that he considered the 'places' to be defined by the signs of the zodiac.

There remains, however, one highly significant passage in which he offers a definition of the houses. It is contained within his method of determining length of life and Ptolemy explains that for a matter of such importance, the planets from which we draw judgement must be located in the powerful places, which he describes as follows:


"In the first place we must consider those places .... in which the planet must be that is to receive the lordship of the prorogation; namely, the twelfth part of the zodiac surrounding the horoscope, from 5? above the actual horizon up to the 25? that remains, which is rising in succession to the horizon [ie., 1st house]; the part sextile dexter to these thirty degrees, called the House of the Good Daemon [11th house]; the part in quartile, the midheaven [10th house]; the part in trine, called the House of the God [9th house]; and the part opposite, the Occident [7th house]". (Claudius Ptolemy, Tetrabiblos, English translation by F.E. Robbins, Harvard University Press, Loeb Edition, 1980, p.273-275)

First we should be clear that this is all that Ptolemy has to say on the technical basis of the houses. In assessing its importance, the introductory comment on the 1st house is the one that is most pertinent: the twelfth part of the zodiac surrounding the horoscope, from 5? above the actual horizon up to the 25? that remains, which is rising in succession to the horizon. The 5? misplacement from the ascendant has caused much debate, the only sensible explanation is that the virtue of each house has been assigned a 5? influence before the cusp, as in traditional use. The same approach is used today by astrologers schooled in traditional techniques, so that if a planet is within 5 degrees of the next house cusp, it is considered to have its influence within the context of that house. But on the basis of Ptolemy's comment here, some authorities have sought to formally recognize a new house construction method, the Classical house system, which is generally said to follow Alcabitius, but with the subtraction of 5 degrees from the Ascendant to find the 1st-house cusp. This definition is misleading, because it is clear that the principle of recognising the five degrees preceding a house cusp is written into traditional technique, regardless of the house method in use, so this should be considered a principle of house interpretation rather than a method of division.

The reference to the "twelfth part" of the zodiac appears confusing because we are accustomed to numbering the signs from the ascendant in an anti-clockwise direction following the numerical order of the houses, although the reason the houses are so numbered is because this is the order in which they rise through diurnal motion. Neither Ptolemy nor Manilius attributed numbers to the houses but described them instead by their names and aspectual relationship to the ascendant. The fact that he makes a distinction between the places of heaven and the parts of the zodiac, and that he introduces this numeration here (though not for the houses), suggests that he recognised them as two discrete frames of reference which were not dependant upon each other, even if in practice they were often associated. His further comment, that the first house is counted from 5? above the horizon up to the 25? remaining again shows that the principle of his house system was not based upon a simple association with the signs, as in the whole-sign method, although he was clearly seeking to perceive the houses as equal divisions which would easily compliment their use.

MarkC wrote:As Gjiada has already suggested not everyone who has studied Ptolemy would accept your conclusion that that he makes no reference that could be construed as indicating his use of houses.

I didn't quite say that. I said that there is nothing that can be construed as any quadrant house system (Placidus et al.) in either text, and that the one slight hint Ptolemy gives with regard to houses in the TB points rather to an equal division. I fully agree with Deb that:

There remains, however, one highly significant passage in which he offers a definition of the houses.

(this is III.10, which I have mentioned a number of times already) -- and that:

we should be clear that this is all that Ptolemy has to say on the technical basis of the houses. [...] he was clearly seeking to perceive the houses as equal divisions which would easily compliment their use.

I didn't quite say that. I said that there is nothing that can be construed as any quadrant house system (Placidus et al.) in either text, and that the one slight hint Ptolemy gives with regard to houses in the TB points rather to an equal division.

Hello Martin,

Sorry I missed your reference to this earlier in the thread.In particular your point:

Almagest II contains no discussion of house systems, and Tetrabiblos very little -- just that snippet in III.10 about various houses being in aspect to the ascendant, which suggests equal houses.

Still for the benefit of Skyscript readers I do think its helpful to see the specific reference you have referred to rather just than accept your assessment. I find it hardly surprising that the Almagest contains no astrological houses. It was after all a work purely devoted to astronomy.

Here is an article by Robert Schmidt from the CURA website that gives consideration to the development of houses in the hellenistic tradition. It includes discussion of Ptolemy's description of houses in the Tetrabiblos.

http://cura.free.fr/quinq/02schmi.html

MarkC wrote: Still for the benefit of Skyscript readers I do think its helpful to see the specific reference you have referred to rather just than accept your assessment. I find it hardly surprising that the Almagest contains no astrological houses. It was after all a work purely devoted to astronomy.

OOps, it was me that mentioned Almagest.

Because it was mentioned in the correspondence (1588) between Girolamo Diedo and Francesco Giuntini. And it seems that Placidus agreed with them.

Anyway I just meant that different scholars as Martin or Bezza of Giuntini or Placidus had different point of views.
So maybe Ptolemy's text is not so clear.

Margherita

MarkC wrote:Still for the benefit of Skyscript readers I do think its helpful to see the specific reference you have referred to rather just than accept your assessment.

Absolutely. I think there is too much accepting of others' assessments going on already. I believe I did paraphrase TB III.10 (or III.11, depending on the edition used) early on in this thread.

I find it hardly surprising that the Almagest contains no astrological houses. It was after all a work purely devoted to astronomy.

Precisely. Therefore, invoking it to support Placidus houses (or any house system) is hardly meaningful.

The system itself is older than both Placidus and Magini; it was known to Abraham ibn Ezra in the 12th century. Similarly, the 'modus rationalis' of Regiomontanus was known long before his time and may have originated with al-Jayy?n? in the 11th century. A good place to look for this sort of information is J.D. North's Horoscopes and History (1986).

Hello Martin,

Thats interesting. As I have noted on another forum section elsewhere on skyscript 'Horoscopes and History' has been out of print for many years and copies are extremely hard to get. I am fortunate that the National Library of Scotland retains a copy of all books published in the United Kingdom. I hope to research the edition kept there soon.

The Warburg Institute in London were meant to be producing a new edition but it has yet to appear.

In the meantime could you kindly give us the reference J.D. North uses alluding to Ibn Ezra's knowledge (use?) of the Placidus house system? Which of Ibn Ezra's books indicates this?

Thanks

Mark

MarkC wrote:As I have noted on another forum section elsewhere on skyscript 'Horoscopes and History' has been out of print for many years and copies are extremely hard to get. I am fortunate that the National Library of Scotland retains a copy of all books published in the United Kingdom.

Happily for me, the astronomy dept. at Lund University has one too. I hope Warburg does produce a new edition.

In the meantime could you kindly give us the reference J.D. North uses alluding to Ibn Ezra's knowledge (use?) of the Placidus house system? Which of Ibn Ezra's books indicates this?

Here is what North says:

On the face of it, the method seems to be that intended by Abraham ibn Ezra in his S?fer ha-moledot (Liber nativitatum) composed at B?ziers in its two versions in 1148 and 1154, as well as in the Keli ha-ne?oshet (Tractatus de astrolabio), evidently translated in England between 1158 and 1161, and also that in his book on the foundations of astronomical tables.

A footnote refers the reader to ch. xi of J. M. Mill?s-Vallicrosa, Estudios sobre historia de la ciencia espa?ola (Barcelona 1949) 'for a general study'.

Martin Gansten wrote:As the Almagest shows, he clearly had the mathematical tools to devise most or all of the quadrant systems we know today. And yet, as the Tetrabiblos shows, he didn't. 'Mikes you fink, don' it?'

Yes Browsing through Almagest, the question comes: which one - ecliptic or horizon - was base coordinate system for Ptolemy... At least one of those definitions in Tetrabiblios where he takes 90 degrees to get to Midheaven, is to take them "upward" (upper square). And he made at least one remark to the system of primary directions beeing the method commonly used, which he disagrees with, so he devises a new his own semi-arcs method (pity that he didn't described this one commonly used he disagreed with... ). Was ascendant a point on horizon for him, or was it a point on ecliptic? For a century earlier' Manilius, there was no ascendant at all. It was just orient - the place where sun rose. Looking from few centuries "after" him, when this horizontal frame was neglected and forgotten, and eclitpic only used, this seems quite convincing as equal house system as we call it today. But looking from his predecessors' point of view (especially babylonian ones) and ignoring his followers, the notion that this was asc-zenith circle comes to mind.

I used the Tetrabiblos translation of Shepherd Simpson http://www.geocities.com/astrologysources/index.htm http://www.geocities.com/astrologysourc ... /index.htm
Book III10 http://www.geocities.com/astrologysourc ... htm#side47
Perhaps Ptolemy rejected the seasonal hours when he mentioned the 'usual traditions' preferring equinoctal hours as more natural. I'm not very familiar with the Almagest but another reason for giving the tables of conversion from seasonal to equatorial hours could be for using only the equatorial rather than the seasonal hours system. Now we are so used to using equatorial hours for our mechanical clocks that we feel a bit ill at ease to convert to seasonal hours. In Ptolemy's days the whole antique world used the seasonal hours and perhaps Ptolemy wanted to use equinoctal hours which could have caused some feelinges of unaccostumedness to his contemporaries.

Another explanation could be that Ptolemy rejected the more crude system of the rising times of whole signs mentioned in Yuzuru's 's link http://www.antonblog.net/astrology/prim ... ons-vol-1/ in the the topic 'Primary Directions for mathematically challenged ?' on Anton Grigoryev's blog on Primay Directions in Tetrabiblos Book III10. His change could then have been to Placidus like methods.

III10 is a bit confusing on the midheaven. The examples he gives are the simplest possibilities. 0?Aries on the eastern and western horizon always gives 0?Capricorn and 0?Cancer in the midheaven respectively. These will be the same in both equal house system and the quadrant systems. The times of 0? to reach the horizon or meridian is easy to calculate and will be the same in every house system. However he seems to give a complicated example for 0?Aries that has passed 3 hours after the meridian.

According to the Placidus method the result will be 64 which is the same as according to Ptolemy. However I have found another method which gives a similar result. I used the following data to make the calculations with a calculator. For ease I used decimals.
Alexandria 30,4 http://www.sacred-texts.com/astro/ptb/ptb59.htm 30?22' footnote 96:2
Obliquity Ecliptic 23,8 The value used by Ptolemy seems to have been used from older sources rather than his own observations as he said http://articles.adsabs.harvard.edu//ful ... 1.000.html
With 0? having past 3 hours after the meridian the sidereal time is 3h or 45? RA 'times', resulting in a MC of 17.54 Taurus
0?Aries = 0? along the ecliptic and 0? along the equator, declination is 0?
0?Gemini = 60? along the ecliptic and 57.75? along the equator, declination is +20.46?
The equatorial distance of 0?Gemini to the meridian is 57.75? - 45? = 12,75?.
Expressed in Placidus mundane positions 0?Aries is 1/4th from the semicircle counted from west to east. Calculation is simple since declination is 0?.
The diurnal arc of 0?Gemini is 205.29. In Alexandria (or rather the alleged position) 0?Gemini rises 12.64 RA times before the equator point on the horizon and sets the same time after. 2 x 12.64 + 180 = 205.29. Divide this by 12 and you get 17.11 the 'horary magnitude' of III10.
The rising point of the diurnal arc of the 'path' of 0?Gemini is measured along the equator from 0?, 135 + 12.64 = 147.64. The position of 0?GEmini measured along the equator was 57.75. The (equinoctal) time that 0?Gemini passed its rising point is 147,64 - 57.75 = 89.98. The time it will take to set is 205.29 - 89.89 = 115.4. 115.4 : 205.29 = 0.562112853. Converted to a semicircle of 180 mundane 'degrees' gives 0.562112853 x 180? = 101.18. 0?Gemini is located in what we would call 11.18 Xth house Placidus mundane. The distance of 0?Aries to 0?Gemini measured along the ecliptic was 60?, measured along the equator was 57.75 and measured in Placidus mundane 'degrees' gives 101.18 - 45 = 56.18?. If we want to convert it to RA degrees to find the time then we calculate 56.18 : 180 = 0.3121111 this was based upon the path of 205.29 so it has to be multiplied by this which gives 64.07 degrees (which then are the years), the same result as Ptolemy's.

However, inspired by Ptolemy's first examples of calculating the time that would pass till 0?Gemini reached the same position occupied by 0?Aries I reasoned that in the last example the time it would take for (17.54?Taurus + 60? =) 17.54?Cancer to reach the meridian would resemble the most to the previous calculations. 17.54?Cancer is 107.54? along the ecliptic and 109.06? along the equator. The distance between this last position and the equatorial position of the meridian is 109.06? - 45? = 64.06? which again are the years. This is in fact resembles a variant of the solar arcs used in secondary progressions. Instead this seems to be a 'MC-arc' direction. The MC moves through the ecliptic and 'pulls' the other planets on its trail in a constantly similar distance to the MC. Even though I don't feel attracted to this (unnatural) involving the planets in the motion of the MC (like I don't feel attracted to solar-arcs either) the advantage is that the natal positions still are concentrated on the ecliptic frame unlike the Placidus type and the Meridian types which introduce 'new' natal chart positions. Could this also be done with the horizon as if the situation would be that the position of 0?Aries would be considered as 3 hours after rising? A sort of 'Ascendant-arcs' directions. I don't think so and I feel inspired by a passage in III10:

Quote Ptolemy: "However, the number of years, determined by the distances between the prorogative place and the destructive planet, ought not to be taken simply or offhand, in accordance with the usual traditions, from the times of ascension of each degree, except only when the eastern horizon itself is the prorogator, or some one of the planets that are rising in that region. For one method alone is available for him who is considering this subject in a natural manner - to calculate after how many equinoctial periods the place of the following body or aspect comes to the place of the one preceding at the actual time of birth, ....". I'm not sure if I interpreted it well, I don't read Greek and the text is still a bit vague. However those who prefer Placidus may be biased too towards interpretation. Probably reading the Tetrabiblos is similar to reading that other biblos, the Bible, subject to interpretation what the reader would like to find. Coincidentally I bumped into a very interesting article of R?diger Plantiko which discusses house systems, their history and Ptolemy. http://www.astrotexte.ch/sources/others/houses.pdf

In this article I read something interesing that could explain something:

"Later astrologers7 have tried to harmonize these statements by introducing the so-called mundane aspects. But it seems more plausible to me that Ptolemy reproduces two different techniques in parallel, taken from two different traditions. Each tradition may have had its own area of validity: The "hermetic" house division may have been the right method for determining the aphetical places, while the astronomically correct Medium Coeli had been used for the computation of directions."


However I might be biased because I don't really feel for Placidus' house division. I agree mostly with the ideas of Johannes Kepler who focused rather on the aspects than the houses and the signs. If I were to use a house system I would choose Equal MC houses for the ecliptic reference frame and the Meridian houses for the equatorial frame. I prefer thes because they use normal coordinate systems (with poles perpendicular to the base plane which at its turn is divided equally) and they are based upon a moving plane (rather than Campanus and Horizon wich also use normal coordinate systems yet are based upon 'stiff' or 'rigid' planes). I think these systems are modern or even could be called post-modern because the Ascendant is reduced to a mere sensitive point in one of the houses rather than the fundamental point of a house system.

Eddy wrote:I used the Tetrabiblos translation of Shepherd Simpson

Any relation to Homer? This is the old (1940) Robbins translation.

I'm not sure if I interpreted it well, I don't read Greek and the text is still a bit vague.

In context it's actually quite clear: Ptolemy objected to directing all points using rising times; or, put differently, to always treating the significator as though it were located on the eastern horizon. This is a procedure you will find in many Greek works, e.g., those of Valens or Paul of Alexandria ('the usual tradition').

Any relation to Homer? This is the old (1940) Robbins translation.

Bart's uncle . Thanks for the clarification. I found something about the differences between Ptolemy and his contemporaries in this article of Mark Riley.
http://www.csus.edu/indiv/r/rileymt/PDF ... etical.pdf