Hello everyone,

I know the rationale behind time based house systems, like Placidus or Koch, but I'm not able to get to the bottom of how house size is determined in the above two systems.
That is, whether each house would be small, medium or large for different times during the day.

I've been playing around with charts, using Solar Fire, and have been getting some frustrating results. It seems that for each time of a given day, house size shifts (getting larger or smaller), based on real time movement. It also seems to be independent of the rationale behind the two above systems.

Placidus: even though the rationale is dividing the day and night halves of the chart, each into 6 equal time-portions, house size in each of the day or night hemisphere houses is unequal (even relative to the MC-IC axis).

Koch: I took a given degree, progressed it from the AC to the MC and divided by 3. For each of those 3 time-portions I've noted where the given degree should have been and it seems inaccurate. And again, the size of the houses for different increments of a given day give uncorrelated results to the 3 time-portions which are in underlaying mechanic for Koch.

Is it just Solar Fire which animates inaccurately?
Is there something I'm missing?

I have never bothered with Koch (or any other modern house system), but the Placidus system is based on the semi-arc of each individual point. The degree of the ecliptic that is on the 12th-house cusp at any given point in time is the one that has completed 1/3 of its semi-arc from rising to culminating at the place in question; the degree on the 11th-house cusp has completed 2/3 of the same arc, etc.

There are many ways to classify house systems like quadrant and non quadrant systems but in the 2 articles below Graham Bates uses the method of Ralph William Holden based on his book 'The Elements of House Division'(1977) reprinted by the Faculty of Astrological Studies
https://www.uraniatrust.org/astrology/a ... -of-houses
https://www.uraniatrust.org/astrology/c ... e-not-flat

Bates reminds us that 'The cusps have two functions. Firstly, they determine the sign ruling the house and so the house's ruling planet. Secondly, they determine the division between houses, but not necessarily the start of a house.' (Ref to CA p. 33 and 151) when Lilly gives a 5 degree orb of influence that precedes the cusp of a house. You have probably noticed that Gauquelin's research found the peak of Mars slightly behind the degree of the Angular Houses. My assumption is that we would find a different picture if he had incorporated other elements of the planets. For example, 'when the declination is of a contrary nature to the latitude, the body will be the nearest to the prime vertical at its rising and setting.' (Howard Patterson, 1917, The Navigator's Pocket-book, p.121-22)

And Houses can be classified in 3 groups
Space Systems, Time Systems and Ecliptic Systems. Each having their pros and cons.

In the 2 systems you mention, both being Time Systems

Placidus has similarities with Alcabitius but is centered on the semi-arcs between rising and culminating.
Koch uses the semi-arc of the ascendant (how long it would take for the chart ascendant to become the MC). You start with the semi-arc of the MC: working back from the chart's time to an earlier time when the chart's MC was the ascendant. You then trisect this in the usual way and take the ascendants for these times as the house cusps.

My personal approach is not so much to find out which system is better but to determine the purpose behind the use of each system.
For example, Whole Sign system might be a good way to determine the strength of a planet and the use of Lots is based on this system like how many signs separate a Lot from the ASC sign but if you want to time a direction, you will need a Time System. And if you are considering moving to another location, a Space System might give you better results.
One of the most common way people disagree over house systems is the focus on the ecliptic. Even siderealists point to the ecliptic (strange isn't it). But you have many more parameters to a planet: latitude (on the ecliptic and mundane), declination, visibility etc.
Here is a planetary fact sheet
https://nssdc.gsfc.nasa.gov/planetary/factsheet/

Another interesting link
Ryhan Butler discussion on Twitter about 14 House systems
https://twitter.com/i/events/997505574127460353

And below who uses what and for what reasons (between Porphyry, Whole Sign and Placidus)
https://www.costarastrology.com/house-systems

Hi DG,

My primary advice would be to employ the Equal House system (as I do), so you don't need to lose sleep over the complexities of time based houses!

That being said, to Ouranos' explanation:

Ouranos wrote:In the 2 systems you mention, both being Time Systems

Placidus has similarities with Alcabitius but is centered on the semi-arcs between rising and culminating.
Koch uses the semi-arc of the ascendant (how long it would take for the chart ascendant to become the MC). You start with the semi-arc of the MC: working back from the chart's time to an earlier time when the chart's MC was the ascendant. You then trisect this in the usual way and take the ascendants for these times as the house cusps.

I would add that ASC and DSC are constantly shifting on the local horizon, even though in the two-dimensional projection onto a chart the IC/MC axis appears to do the shifting.

Hope this helps to clarify the matter for you!

Michael

Martin: In principal it's easy to understand. It becomes more difficult when you try to show it to students on Solar Fire

Ouranus: Thanks for the links, definitely will go through a few of them. Also I wasn't aware of the ecliptic house systems, will go over it as well.
--
About the Gauquelin sectors, indeed they stretch into the cadent house and
we have the 5 degree rule by Lilly and others.
--
Why do you think that siderealists referring to the ecliptic is strange? Precession is in progress over the the plane of the ecliptic.

Michael: Equal, do you? I usually use Placidus and Whole sign for natal work, and Regiomontanus and a bit of whole sign for Horary.
When I want to be more exact, I compare Placidus to Alcabitius to Regiomontanus and see where cusps 2,3,5,6,8,9,11,12 fall on.

Anyways, thanks all for input.

Dima Gur wrote:Martin: In principal it's easy to understand. It becomes more difficult when you try to show it to students on Solar Fire

Not if you really understand the principle (I think). Here's how I would do it:

1. Note the degree on the ascendant at a given time.
2. Animate the chart to find at what time the same degree reaches the MC.
3. Divide that time by 3 and add it to the original time, then animate the chart to the resulting time, and you will find the degree in question on the 12th Placidus cusp.
4. Add the same amount of time again, animate the chart, and you will find the same degree on the 11th cusp.

Thanks Martin,
Will try, and report if my memory will not fail me.

Why do you think that siderealists referring to the ecliptic is strange? Precession is in progress over the the plane of the ecliptic.

Fixed stars are part of the constellations and the projection of the Earth's orbit onto the celestial sphere will be projected on the ecliptic.

Here is how Ryhan Butler explains it here
https://www.medievalastrologyguide.com/fixed-stars

"We simply drag the star to the point on the ecliptic it is closest to. For some stars like Spica, Regulus, and Antares it’s fairly simple because they are already very near to the ecliptic to be included within the zodiac band which stretches to 8° either side of the ecliptic so it makes sense to say that they occupy some degree of the zodiac. Other stars – particularly non-zodiacal ones - are much further away so their projection onto the ecliptic comes with different problems.
Let’s take for example Spica and Arcturus and as another pair Sirius and Canopus. Spica is positioned at 2° south of the ecliptic so is below the line; Arcturus is almost 31° north of the ecliptic, so they are separated by 33° of space north and south. However, when you project the positions of these stars onto the ecliptic they are nearly right on top of each other. Spica is located at 24° 07’ of Libra while Arcturus is at 24° 31’ of Libra. Less than half a degree distant."
"And in the north, there are many stars that never rise or set at all; these “circumpolar stars??? .

Now, imagine the Sun or any wandering star never rising or setting. Impossible you will say but this is something some Fixed Stars do.
Or even because of some high latitude, Mars would be conjunct Venus even though they would have opposite latitude.
And why use the ecliptic for the Fixed Stars and not the constellations which are not equal to 30 degrees?
Every 72 years the precession will make the stars move about 1 degree. And here is another challenge. Look up the number of ayanamsas which have been defined over the centuries. As per my siderealist friends, Khrisnamurti seems to be the best one. But it ain't easy to follow when you have a companion called the ecliptic.
And we have not even discussed the asteroids and the deep sky. Hours of pleasure ahead of us!

Dima Gur wrote:Michael: Equal, do you? I usually use Placidus and Whole sign for natal work, and Regiomontanus and a bit of whole sign for Horary.
When I want to be more exact, I compare Placidus to Alcabitius to Regiomontanus and see where cusps 2,3,5,6,8,9,11,12 fall on.

I experimented with various house systems in the past, however, I find Equal Houses to not only give accurate descriptions, but also to be aesthetically most pleasing and consistent with the mathematical/geometric foundations which the art and science of astrology rests on. As I explore in depth in my forthcoming book.

What it boils down to is that symmetry and simplicity are key to understanding in natural and occult philosophy. That's my perspective anyway. Your mileage may differ.

Dima Gur wrote:Why do you think that siderealists referring to the ecliptic is strange? Precession is in progress over the the plane of the ecliptic.

I overlooked this earlier, but I agree completely with Dima here. The ecliptic is the apparent path of the sun relative to the constellations. The sidereal/tropical distinction is simply about defining a starting point somewhere along that circle.

As is often the case, a historical perspective helps to clarify things: the ecliptic was first defined by the Babylonians, prior to the introduction of the tropical zodiac.

In Britannica
https://www.britannica.com/science/astr ... -divisions

"The Mesopotamian arrangement of constellations has survived to the present day because it became the basis of a numerical reference scheme—the ecliptic, or zodiacal, system. This occurred about 450 BCE, when the ecliptic was clearly recognized and divided into 12 equal signs of the zodiac. Most modern scholars take the zodiac as a Babylonian invention; the oldest record of the zodiacal signs as such is a cuneiform horoscope from 419 BCE. However, as Greek sources attribute the discovery of the ecliptic to Oenopides in the latter part of the 5th century BCE, a parallel development in both Greece and Babylon should not be excluded.
Ptolemy’s star list presents a curious puzzle. The southernmost heavens, invisible at the latitude of Alexandria, naturally went unobserved. On one side of the sky near this southern horizon, he tabulated the bright stars of the Southern Cross (although not as a separate constellation) and of Centaurus, but on the opposite side a large area including the first-magnitude star Achernar had been left unrecorded. Because of precession, before 2000 BCE this region would have been invisible from Mesopotamia. Perhaps neither Hipparchus nor Ptolemy considered that part of the heavens unnamed by their ancient predecessors."

If we consider "the Almagest of Ptolemy as a mere compilation who measures about 1,022 stars grouped into 48 constellations", my question here is why has it been diluted and almost lost in modern sidereal zodiac? Why so much emphasis on the zodiac signs? And considering the physical location of the Mesopotamians, the southernmost heavens went unobserved.
"Ecliptic coordinates predominated in Western astronomy until the Renaissance but with the advent of national nautical almanacs, the equatorial system (right ascension measured from the first degree of Aries and declination) analogous to terrestrial longitude and latitude is customarily divided into 24 hours rather than 360 degrees", emphasizing the clocklike behaviour of the sphere and the predominance of the tropical zodiac.

Just asking as a devil's advocate here and as always I am welcoming different viewpoints to keep learning.

Ouranos: would I be right in assuming that your questions are based on an unstated assumption that a 'sidereal zodiac' ought to include as many fixed stars and constellations as possible?

The zodiac is just a belt of sky surrounding the ecliptic within which the visible planets are seen to move. This is equally true regardless of which point we define as our starting point. Whether you are a tropicalist or a siderealist, the planets will be observed among the same constellations. The only difference is whether you anchor the zodiac to the constellations or to the seasons. (The issue is complicated by the fact that many ancient astrologers imagined they could do both, because they didn't understand precession.)

"Ecliptic coordinates predominated in Western astronomy until the Renaissance but with the advent of national nautical almanacs, the equatorial system (right ascension measured from the first degree of Aries and declination) analogous to terrestrial longitude and latitude is customarily divided into 24 hours rather than 360 degrees", emphasizing the clocklike behaviour of the sphere and the predominance of the tropical zodiac.

I don't understand what the tropical zodiac has to do with the rest of this passage. As someone who works with the equatorial system (in the form of primary directions) all the time, I can assure you that it is not contingent on a particular definition of the zodiac.