Skyscript Astrology Forum

Hi there,

I'm opening this topic to see if I can understand Sidereal Astrology a little bit better in order to try to integrate it with my open-source software implementation: https://github.com/flatangle/flatlib.

One of my main doubts is if sidereal astrology techniques are coherent with the tropical astrology techniques. In other words, could we say that sidereal astrology, in a practical point of view (which is what matters to the computer, zeros and ones), is the same as tropical astrology + offset of signs? Or there are more practical differences?

For instance, in this line of my library code, I'm declaring that Aries, for instance, is a spring sign. Is it the same for sidereal?

Or Aries, in a sidereal point of view, is not a spring sign? This implies practical differences: for instance in the computation of the Temperament, the sun season is one of the parameters. There are more "small" things like this, but I'm slowly accessing if it is worth to implement the sidereal zodiac in the software library..

Any thoughts on these matters?


Thanks,
Jo?o Ventura

This is a big question, Jo?o. For starters, do you have time to read this article? http://www.snowcrest.net/sunrise/aatriplicities2013.htm

Many differences are discussed here on this forum. The sidereal zodiac has no relationship to the seasons. Martin will no doubt be replying to your questions as he has time.

For your software, for the time being, it might be best to simply give the math of sidereal options, without interpretations.

Therese

I'm very glad you're looking into this, Jo?o. From the chart calculation point of view, there's no difference I can think of except for the offset of signs. Interpretation is a different matter, and of course temperament belongs to the realm of interpretation, even if we try to codify and program it.

One way of answering your question (and, I believe, a necessary answer) would be to say that, despite the name of this forum, there is no 'sidereal astrology' as such. There are just two basic ways of defining the starting point of the zodiac: the sidereal and the tropical, which are often mixed up in ancient sources because the issues involved weren't properly understood, though I think it's fair to say that the sidereal definitions are somewhat prior both conceptually and historically. But many varieties of astrology have been practised using a sidereal zodiac (that is, a zodiac not beginning with the equinox) -- Babylonian, Hellenistic, medieval Perso-Arabic, Indian, modern western -- which is why 'sidereal astrology' doesn't (or shouldn't) really connote anything except the use of such a zodiac.

Naturally, any sort of technique that is based on the seasons, or at least on an unchanging relationship between seasons and signs, would be incompatible with a sidereal zodiac, where the signs are fixed with respect to the stars and movable with respect to the seasons. This would affect some Ptolemaic doctrines in particular. On the other hand, I could argue that sidereal Aries is still a spring sign here in Scandinavia (where mid-April to mid-May definitely counts as spring), whereas the designation would be fairly meaningless (irrespective of which zodiac we use) near the equator, for instance in northern Brazil, and simply wrong in New Zealand.

jventura wrote: One of my main doubts is if sidereal astrology techniques are coherent with the tropical astrology techniques. In other words, could we say that sidereal astrology, in a practical point of view (which is what matters to the computer, zeros and ones), is the same as tropical astrology + offset of signs? Or there are more practical differences?

There may be some programming implications - though I'm not fully sure what you've included in the software nor how you go about calculating things. As far as I know you are using the swiss ephemeris which may well include all the calculations anyway, but I'm not sure what you include or what the swiss ephemeris does.
If you are calculating something like antiscia just keep in mind it won't be enough to, say, subtract X degrees to get the sidereal zodiac and then keep calculating antiscia points from that zodiac. Certain things really are linked exclusively to the equinoxes and solstices and this is one good example of that.

I'm not sure what sidereal astrologers do with straight and crooked signs though, I was going to ask that here. Recently Martin made a post on the straight and crooked signs:
http://skyscript.co.uk/forums/viewtopic ... 40&start=0

So I was wondering if that list is updated in sidereal astrology to reflect the displacement by one sign of the straight and crooked list? If so, and if your program includes that kind of information, this is another place where it would need some updating.

(Edit: I presume that sidereal astrologers also use antiscia etc. and mark it by the solstices rather than the signs btw, but perhaps not)

Paul wrote: If you are calculating something like antiscia just keep in mind it won't be enough to, say, subtract X degrees to get the sidereal zodiac and then keep calculating antiscia points from that zodiac. Certain things really are linked exclusively to the equinoxes and solstices and this is one good example of that.

Hi Paul,

yes, that was the kind of questions that I was trying to raise. So far, the code in flatlib assumes that 0? Aries is the Vernal Point and any changes can bring inner inconsistencies.

As in your example, this is how I calculate the antiscia and contra-antiscia and I'm basically assuming that 0? Aries is the Vernal Point.

I will still give some more thought on this matter, but if it proves cumbersome, I will just add functions to relocate objects on a chart (as per Martin's suggestion) so that people may be able to, at least, print a chart considering another zodiac start.


Jo?o Ventura

jventura wrote: yes, that was the kind of questions that I was trying to raise. So far, the code in flatlib assumes that 0? Aries is the Vernal Point and any changes can bring inner inconsistencies.

As in your example, this is how I calculate the antiscia and contra-antiscia and I'm basically assuming that 0? Aries is the Vernal Point.

Right, so it's going to be a matter of separating out your dependancies perhaps. You may have to assume a tropical zodiac for the majority of calculation, whereas something like dignities or chart drawing ought to have some dependency to inform it about how to render itself. Really something like antiscia can be agnostic about which zodiac is used by the end user. I'm not sure if something like that comes with swiss ephemeris as I've no experience with using it.

But really something like this should be calculated with the tropical zodiac first, and then, later, in a kind of MVC pattern, when rendering the chart it will know to begin 0 Aries from some subtraction, which is 0 for the Tropical Zodiac but will be differentiated for the other sidereal zodiacs. There will need to be some decoupling perhaps.

Btw to the sidereal astrologers, I say this not in some tropical supremacy way, but merely in terms of ease of programming, this would be just less complicated.

Just a quick reply: yes, antiscia are points connected by their identical declinations (and the attendant diurnal and nocturnal semi-arcs), so they are not really related to the zodiac as such. I don't use them myself, but they definitely need to be calculated with reference to the solstice/equinox points, whether or not one considers those points to define the zodiac.

(As an aside, the Greek fascination with this sort of pattern -- similar rising and setting times, etc -- predates the astrological use of the tropical zodiac, as reflected in one or two places in the Tetrabiblos, where it is clear that Ptolemy has taken over techniques originating in a zodiac that had the solstice/equinox points in the middle of their respective signs.)

Paul wrote:I'm not sure what sidereal astrologers do with straight and crooked signs though, I was going to ask that here. Recently Martin made a post on the straight and crooked signs:
http://skyscript.co.uk/forums/viewtopic ... 40&start=0

So I was wondering if that list is updated in sidereal astrology to reflect the displacement by one sign of the straight and crooked list?

To be honest, I've never seen any sidereal astrologers use that distinction at all, though I suppose some might. (Actually, I'm not even sure I've ever seen a tropical astrologer use it.) The Indian Tajika authors just give the standard Arabic list, despite using a sidereal zodiac. I'm not sure they understood the implications.

Martin Gansten wrote:(As an aside, the Greek fascination with this sort of pattern -- similar rising and setting times, etc -- predates the astrological use of the tropical zodiac, as reflected in one or two places in the Tetrabiblos, where it is clear that Ptolemy has taken over techniques originating in a zodiac that had the solstice/equinox points in the middle of their respective signs.)

Martin,

do you have the references for this idea handy? It sounds like the Mesopotamians' ideal year which placed the Equinox points in the middle of their months instead of the beginning. I believe Geminus talks of it too referring to it as ancient or of the ancients.

Konrad wrote:Martin,

do you have the references for this idea handy? It sounds like the Mesopotamians' ideal year which placed the Equinox points in the middle of their months instead of the beginning. I believe Geminus talks of it too referring to it as ancient or of the ancients.

It's somewhere in the length-of-life procedure (3.10 or 3.11 depending on what edition you use). Ptolemy describes the potentially killing aspects, including sextiles when they fall between signs 'seeing' and 'hearing' each other. Those are supposedly (according to Tetrabiblos 1.15) the signs sharing the same horary times; but in Ptolemy?s tropical zodiac, no such signs are in sextile aspect to each other!If the solstices fell at 15? Cancer and Capricorn, then Gemini and Leo would share the same horary times, as would Sagittarius and Aquarius.

There may be something else, but this is the one I can place at the moment.

Martin Gansten wrote:

Konrad wrote:Martin,

do you have the references for this idea handy? It sounds like the Mesopotamians' ideal year which placed the Equinox points in the middle of their months instead of the beginning. I believe Geminus talks of it too referring to it as ancient or of the ancients.

It's somewhere in the length-of-life procedure (3.10 or 3.11 depending on what edition you use). Ptolemy describes the potentially killing aspects, including sextiles when they fall between signs 'seeing' and 'hearing' each other. Those are supposedly (according to Tetrabiblos 1.15) the signs sharing the same horary times; but in Ptolemy?s tropical zodiac, no such signs are in sextile aspect to each other!If the solstices fell at 15? Cancer and Capricorn, then Gemini and Leo would share the same horary times, as would Sagittarius and Aquarius.

There may be something else, but this is the one I can place at the moment.

Great, thanks!

Martin wrote:(As an aside, the Greek fascination with this sort of pattern -- similar rising and setting times, etc -- predates the astrological use of the tropical zodiac, as reflected in one or two places in the Tetrabiblos, where it is clear that Ptolemy has taken over techniques originating in a zodiac that had the solstice/equinox points in the middle of their respective signs.)

I think there's enough evidence via various texts for us to be confident that older sources recognised the equinox as falling in the middle of the signs, so that the signs were divided by it. By Ptolemy's time precession had brought the equinox from the middle of sidereal Aries to the beginning of Aries, and at the time Ptolemy makes it clear that wherever the equinox falls, that point will be 0? Aries. Are we in agreement that, in either of these ancient approaches, the motivation was to have a zodiac that identified the equinoxes and solstice points?

Re straight and crooked - Dorotheus uses this, but I'm assuming you know about that. If not, I'll provide a ref.

Martin Gansten wrote:Just a quick reply: yes, antiscia are points connected by their identical declinations (and the attendant diurnal and nocturnal semi-arcs), so they are not really related to the zodiac as such. I don't use them myself, but they definitely need to be calculated with reference to the solstice/equinox points, whether or not one considers those points to define the zodiac.

I think to be more precise, they are only connected via the declination of one body alone - the sun. Two planets on the same declination are not necessarily going to be at the antiscia of each other. I say this just in case it occurs to anyone to calculate the declination of any given planet and use this to determine that it might be antiscia another at the same declination. Once the planets' latitude is taken into account they may not be in each other's antiscia after all.
I am highlighting this more for any programmer who has access to the declinations already and hope to bypass any 'problems' of including the zodiac by sidestepping them straight into checking planets which are of the same declination to determine if they are in each others antiscia. In the sense that the tropical zodiac can be said to be defined by the declination of the Sun, they conform to the tropical zodiac - even if accidentally.

As an aside, the Greek fascination with this sort of pattern -- similar rising and setting times, etc -- predates the astrological use of the tropical zodiac, as reflected in one or two places in the Tetrabiblos, where it is clear that Ptolemy has taken over techniques originating in a zodiac that had the solstice/equinox points in the middle of their respective signs
...
Those are supposedly (according to Tetrabiblos 1.15) the signs sharing the same horary times; but in Ptolemy?s tropical zodiac, no such signs are in sextile aspect to each other!If the solstices fell at 15? Cancer and Capricorn, then Gemini and Leo would share the same horary times, as would Sagittarius and Aquarius.

That's a good point Martin, I wasn't aware of that reference before, or didn't realise its implication. It means that Ptolemy is likely getting this from an older Babylonian source - like where in Systems A and B, Leo and Gemini are tabulated with having equal daylight.

To be honest, I've never seen any sidereal astrologers use that distinction at all, though I suppose some might. (Actually, I'm not even sure I've ever seen a tropical astrologer use it.) The Indian Tajika authors just give the standard Arabic list, despite using a sidereal zodiac. I'm not sure they understood the implications.

Ye it's not really a big deal for me, I was just more curious if sidereal astrologers 'update' the list as it were.