• Search
  • Lost Password?

The Zodiac Debate: Tropical vs Sidereal

The Zodiac Debate: Tropical vs Sidereal

In episode 60 of the podcast astrologers Kenneth Miller and Nick Dagan Best join the show in order to help me tackle the zodiac debate, and discuss the differences between the tropical and sidereal zodiacs.

Below are notes on some of the topics that we discussed in the episode, followed by the link to listen to the recording of this episode of the podcast.

Outline of the Episode

Here is an outline of some of the main points that we focused on during the course of this episode, based on the show notes that were prepared before we talked:

  • There are three zodiacs: constellational, sidereal, and tropical.
  • Started with the constellations along the ecliptic.
  • Ecliptic is the path the planets take across the sky. Only goes through certain constellations
  • By the 5th century BCE the zodiacal signs were standardized in Mesopotamia.
    • Sidereal zodiac with 12 signs of 30 degrees each.
    • The constellations themselves are uneven, but the “signs” are not.
  • Later by the 2nd century we see Ptolemy firmly adopt the tropical zodiac.
    • Based on the solstices and the equinoxes.
    • More connected with the seasons.
  • In this period the zodiacs were roughly aligned, so there was no issue.
  • Due to precession they move about 1 degree every 72 years.
    • Minor change in a lifetime, but adds up over centuries.
    • 25,772 years for a complete cycle
  • Today the tropical and sidereal zodiacs differ by about 24 degrees.
    • Subtract about 24 degrees from a tropical position to get sidereal position.
    • A planet at 14 Aries in tropical is around 20 Pisces in sidereal.
  • Who uses tropical now?
    • Tropical is primarily used by western astrologers since the middle ages.
    • All Sun-sign columns use the tropical zodiac.
  • Who uses sidereal?
    • Sidereal mainly used by Indian astrologers.
    • In the 20th century some western astrologers started using sidereal. General called “western sidereal astrology” now.
  • Brings us today where there is a debate between astrologers about which is best to use.
    • This is a genuine technical debate that has decent pros and cons on both sides.
    • It is complicated by the long traditions behind each, and the tendency for astrologers to identify with their chart placements.
  • Separate issue is the use of precession as an attack vector by skeptics.
  • Astrologers have to settle this as a technical, conceptual, and practical issue.
  • Some questions to ask:
    • Do tropical and sidereal astrologers use the zodiac in the same way?
    • Do they attribute the same qualities to the signs?
    • Is it the case that one approach is valid and the other is not valid?
    • Or is it possible that both are valid in some way?
  • Attempts to answer the question from a historical perspective:
    • One potential way of answering this is figuring out what zodiac the ancients originally intended to use.
    • The problem in the Hellenistic tradition is that they seem to have drawn on both tropical and sidereal considerations.
  • Ultimately what we have to do is go back to the fundamentals and figure out where we are getting each concept from: rulership, modalities, gender, etc.
  • There are important problems that supporters of both approaches still have to resolve:
  • Tropical issues:
    • If the zodiac is based on the seasons, then you run into an issue since the seasons are flipped in the northern and southern hemispheres.
    • This is an issue for the quality of the signs, but also potentially for the rulerships.
    • Either the zodiac should be flipped, or astrologers need to come up with a reason for why the vernal point can act as a starting point that is true in both hemispheres.
    • Tropical astrologers from the southern hemisphere like Australia often report that the zodiac works just fine as is, and should not be flipped. Are they correct, or is this open to question?
  • Sidereal issues:
    • There is no universally agreed upon starting point for the zodiac in sidereal.
    • Since the “signs” are idealized and don’t line up with the constellations perfectly it is not clear where zero degree of Aries should be.
    • The ayanamsha is the difference between the tropical and sidereal zodiac.
    • Different astrologers use different fixed stars and other points to start with.
    • There is a separate issue of whether the idealized signs should be used, or if the actual constellations of varying length should be used.
      • If the constellations then should ones like Ophiuchus be incorporated?
  • Final thoughts.
  • No one has really worked out a good methodology for testing this issue.
  • Astrologers often test it using charts, but sometimes they use precession and historical events and other things.
  • With the problems outlined clearly now at least we can all approach this with a better understanding of what we are dealing with.


A full transcript of this episode is available: Episode 60 transcript

Listen to This Episode

You can either play this episode of the podcast directly from the website or download it as an MP3 to your computer by using the buttons below:

Leave a reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

  • Doesn’t analysis of constellational vs “sign-based” zodiacs depend to a certain extent on whether you think astrology is fundamentally about physical influences vs being a modeling tool (map)? Would seem so to me.

    – Ed

  • Bravo. Excellent podcast guys. I think that ancient astrologers very early on deciding to go with an idealized division of the sky tells us a lot about how they saw things working. Same with Lots, mean conjunction, houses and so forth. Unlike later astrologers, I don’t think they assumed their research was complete by the end of the Hellenistic Age. It seems pretty clear from both a philosophical and a technical perspective that they assumed there was something more critical “under” the chart and the observable cycles.

  • First off I wanted to say I think Chris has really raised the bar in terms of the quality of discussions taking place on these podcasts. Its going to be really a hard act for anyone else to follow and maintain this kind of high standard! I thought all the issues of controversy were well presented in the latest podcast in a very fair and balanced way. A great podcast by all the participants. From my previous experience of such debates I suspect it might have been a little more contentious if you had involved a western siderealist rather than a Jyotish practitioner! Its probably worth pointing out there are still practitioners of constellational astrology in the German speaking world following the example of Rudolf Steiner. In addition we have traditional astrologers following Perso-Arabic astrology who are sidereal. I noted Chris kept saying the tropical zodiac was first adopted in the medieval period. That is only half true. The research of Alexander Jones has demonstrated nearly all the hellenistic astrologers had adopt the tropical zodiac by the 4th and 5th century CE. Still, I accept the picture becomes muddled again in early Perso-Arabic astrology as they originally relied on sidereal tables. On the point about Hipparchus being the discover of precession its worth pointing out that more and more academics seem to now accept that Hipparchus got his information from the Babylonian astronomer-mathematician Kidinnu. Thus several scholars now suggest Kidinnu may be the actual discoverer of this phenomena not Hipparchus. One practical issue I thought it would have interesting to discuss is the use of precession corrected charts by tropical astrologers. This kind of hybrid approach raises interesting philosophical questions. Probably, the highlight of the whole podcast for me were Nick Dagan Best’s comments about the speed of the Sun in various signs ie slow in Leo /fast in Aquarius and fast/getting slower (Aries), slow speeding up in Libra. This was a novel approach to the perennial question of the tropical zodiac in the southern hemisphere. The podcast was worth listening to for that point alone! I’m looking forward to more stimulating podcasts like this.

    • @mark cullen at al – re precessed corrected charts run in tropical . This is the very reason I avoid doing Solar Return charts – because it has been suggested by some professional astrologers that they need to be run in tropical using the sidereal birth time, and for other reasons as well (too much controversy). I ran an astrologer friends SR chart both ways – pre-cessed and non and we are going to talk about the test results at the time of her next birthday. She is a Siderealist who calls herself a Vedic astrologer but i am not sure if she is practicing Western Sidereal or not. I mention this because she becomes vehement when defending Vedic over Western and believes that Western astrologers have no concept of the constellations not lining up with the signs and keeps asking me “what are they going to do, add a 13th sign?” ( which I do not understand). There are many astrologers, western and non, who themselves do not understand the zodiac they are working with nor have examined their belief in causality, synchronicity, correlation etc. I am sure she does not know for example, that some constellations are very uneven in size. The siderealists enjoy the idealized (i.e. forced, neatly packaged) zodiac as much as any westerner. Likewise, many practicing western astrologers are not aware of the decans, and that fixed stars from the previous constellation exist in the next sign, so it is no surprise to me that the public at large would not understand this. This is why these podcasts are so vital – the astrological community itself needs to become informed. Unfortunately, anyone can hang a shingle, and there seems to be no way to control the lack of professionalism/standards required etc.
      On another note – I found it fascinating when the comment came up regarding the eschewing on some level of the symbolism of the signs and focusing instead on planetary qualities attached to those signs. I am not sure what the difference would be unless the classic symbol is being seen as too simplistic (the typical sun sign images) Are the planets themselves not symbols of matter and spirit? And can the visual not have impact? I would take greater issue with attributing the same meaning/quality of a sign’s ruling planet to the house it rules in a “natural zodiac”. For example, if we take the multitude meanings of the 8th H which is known as Scorpio’s home it makes sense on some level to assign the symbolic meaning, such as the desire nature – the intimacy and sexuality, the darkness and transformative quality of having united with another, the resourcefulness and secrecy etc. but the 8th H includes so much more. If, on the other hand we assign the planetary qualities of Mars to this house we get sexuality but what else?, certainly not the money we owe, money from others, taxes, death, secrets uncovered. And the same with Pluto – an incomplete association. Humanistic astrology a la Rudhyar emphasizes modality as much as anything it seems to me. The 8th being the 2nd water house and 2nd H of desire and survival – only now, having to include another, the 12th letting go of all desire bringing the wisdom of all 12 houses to the world again in the first house. I am looking forward to a melding of the old with the new – and even different systems. I think it is possible to find answers as we move forward and to believe that we can have as much insight as the ancients. I think there will be an interface of new discovery in physics with all of this and I hope it is in my life time. Thanks to all for a great podcast.

      • Jen,
        It’s not an easy read, but Marc Edmond Jones wrote a book called “Astrology: How and Why It Works”, in which he analyzes various chart elements based on third and fourth harmonic relationships (though he didn’t call them harmonics). It presents some interesting ways of thinking about houses vs signs, constructing meaning from combinations of fundamental concepts. He certainly influenced Rudhyar.

        – Ed

  • On why the vernal point can be used as a starting point in both hemispheres: Even though western astro is euro-centric and can easily be identified with 4 distinct seasons, I think while this association/correlation naturally developed and influenced meaning, most especially by Northern European readers, it does not necessarily obviate or supersede the essential, intended, and universal meaning of the 1st house of the tropical zodiac as incompletely documented as that might be. I think common, current interpretation of the ist House is that it is about the self, the body, the experience of simply the new beginning of being in the world, the experience of “I am”, the individual personality, the m.o. of the life path to the Sun, (is that last one non-traditional ?) then this could happen in the Autumn in the southern hemisphere just as well as, and independent of, the absence or change in seasonal reference as it exists in Europe. I think tropical astrology works in both hemispheres regardless because the 12 houses of the zodiac are an ordering of the cosmos, the Universe, which operates beyond earthly regional seasons. Since humankind assigned a meaning to that order centuries ago, it resonates and is useful wherever one may be. I see this all the time with Tarot – if I read a card a certain way that may slightly different from another’s interpretation, then when that card comes up in a reading, that is what it means. I do not know how this works, just that it does. When we use astrology we are ordering an internal process that has outward manifestation. Perhaps among the many expressions of each sign, some are more emphasized in a certain part of the world, within a certain cultural context, but this does not preclude the usefulness of astrology or the essential meaning of an astrological house in all other parts of the world. Lastly, any reading, done any where, can be done with a focus on just the cosmos (the signs) or just the solar system (planets and angles) and both these readings can be equally as accurate. One system resonates with the other somehow. Certainly this phenomenon would play into the debate, would it not?

    • But that still leaves you with one huge problem. You say that houses can mean whatever you want then to mean? Ok. But the most important thing about them, something that several here have mentioned, is that they all share the same relative to each other. If you imagine your 4th house as what everyone else experiences as the first house (I can see that happening under the right planetary influences), then you still have to have your 10th house fulfilling what everyone elses’ 7th does. A house isn’t a house. A house is a subdivision of something like a color wheel, and each one of that wheel’s divisions are the same in all relative respects to the other divisions’. So technically, there’s no such thing anyway as the “1st” house, just the early degrees of a 360 degree wheel superimposed over the ecliptic, and defined by the rising. Human kind didn’t “assign a meaning to that order centuries ago.” That order was imposed on us by the universe whole millennia or more in the past. The house concept has been around in astrology in the Far East since possibly it’s first records were kept. That much I’ll check on, but feel free to beat me to it!

      • Gra – No – I did not mean that we can assign any meaning we want to the “places” – the houses. I am much more rule/technique bound that I have conveyed. Currently, I am studying the concept sect for example, and find that to be fascinating and informative. To me, the 4th H will always be the father and the home and roots and foundational security – I see it very connected to the IC and of course, it affects the interpretation the chart is a whole if we wish to approach the chart in an integrated, modern way. I was just trying to relay – in a lay person’s way – that if you are clear on the meanings you are using than that is the filter you read through and what is going to be conveyed to the self and the client. This is within reason of course – I am not about inventing my own system of astrology – far from it. I am in total agreement that the order was not only imposed on us but even more – that we are part of and at one with that order. As above, so below is my bent. Because we are talking here about the tropical house system’s effectiveness for the southern hemisphere I will keep the topic focused there. If I were using the existing system of astrology that was not developed in the southern hemisphere, than I would have to use those meanings would I not?, and just because i can’t see the greening of the earth out my window does not mean I cannot interpret an Aries Sun as a northerner would. Likewise, the first house in the chart would carry the same meaning, relative to the other houses of course, as it would in the north. This reasoning pre-supposes that there is not a causal influence – that the seasons were integral to the design of the meanings, relative to the vernal point, but just one expression of death and re-birth, and an easy one to grab onto because that was seen in the environment. So maybe I am missing something with the actual science here (my weakness) as the vernal point relates to the southern hemisphere which throws my reasoning out the door. Very possible. It just seems like such a leap to say that astrology can only work in the part of the world that is similar to where it originated. Really? This ordering of the cosmos is that specific to place of origin? Please – anyone – feel free to enlighten me. If I move to Australia from the North my bet is that I can use astrology in the same way and see the same results.

        • I too am very interested in Mr. Dagan Best’s findings regarding speed of the Sun – it would be great to pull this all together.

  • A few of things to consider on the subject of why the tropical zodiac may work in the southern hemisphere …..
    -90 % of humanity lives above the equator.
    -Most of the southern hemisphere is water.
    -Most of the southern hemisphere is fairly recently populated. Even the aborigines have “only” been in Australia for the last 40,000 years, the western hemisphere natives “only” around 10,000. These are small time periods in terms of evolution. They are also small populations.
    -The consensus is that early humans first appeared on the northern hemisphere, likely Kenya, and then gradually spread to the south.
    -There were only small populations in the southern hemisphere until the last 500-600 years or so.
    -The primate/hominid/human nervous system has been en-trained by the northern hemisphere sun and seasons for hundreds of thousands of years. This training has taken place in deep areas of the brain.
    We could say that humans are essentially northern hemisphere creatures, and those living in the south have “recently” arrived. They still have northern hemisphere brains. Physical evolution takes place much more slowly than cultural evolution.
    Also …. I really liked the comment Chris made about Mercury being the ancient planet of astrology and representing the ability to hold two ideas in mind.
    This is what astrologers do, holding both the metaphorical/symbolic on mind along with the literal/concrete. With only one of these, astrology doesn’t seem complete.
    Thanks for a great podcast, really enjoyed it!

    • Evolution occurs in both a spatial and temporal environment and then persists for long periods of time. I believe it was Rudhyar who first suggested that humans evolved in the northern hemisphere (imprinting the tropical zodiac there) and only later migrated south bringing the imprint with them.

  • I am not really sure about the validity of the evolutionary point Chet has introduced to suggest early humans evolved in the northern hemisphere. Most of the findings of early humans are in Kenya and Tanzania. Tanzania is south of the equator while the equator runs right through the middle of Kenya. It would probably more accurate to say early humans evolved close to the equator than to heavily emphasize a northern hemisphere vs southern hemisphere origin. Equally, while Aboriginal Australians may only have been in the Continent 40-50,000 years exactly the same point could be made regarding the occupation of Europe and SW Asia by modern humans. One point that is relevant I think is that on a planetary level is that 67.29 percent of land surface area is on the northern hemisphere while only 32.71 percent is on the south hemisphere . That includes Antartica. So on a planetary basis the northern hemisphere spring is when most of the planet ‘greens’ and sees a growth in plant life. Of course on the equator there are no distinct seasons as in the Northern hemisphere. However, as Nick Dagan Best explained the Sun on a planetary level is moving more slowly in tropical Leo and faster in tropical Aquarius regardless of your location. Similarly, we see a shift in gear in solar speed at the equinoxes. So in regards rulerships we dont need to resort to seasonal considerations. These can be explained due to planetary speed.

  • The issue surrounding the precession of the equinoxes, and the resultant [tropical] zodiacal meaning, becomes somewhat irrelevant if one considers that the energies/characteristics portrayed actually emanates beyond the signs. If sidereal astrology works for some people, that’s fine as often times we are interpreting a unique symbolic representation.

    I would be interested to hear a debate regarding the use of certain house systems, particularly as the most commonly used systems completely fails at increasing latitudes. Alcabitus seems to overcome this issue but is rarely used?

    • That’s a common misconception in my opinion. Mike Wackford does a pretty good job of addressing it in his series of articles that start here: http://www.skyscript.co.uk/polar1.html
      You’ll want to read all five parts.
      As far as different uses for different systems, there was the suggestion of Schmidt regarding use of whole sign for topical application, and “some” quadrant system for planetary strength. I’m certainly convinced of the effectiveness of semi-arc based systems for timing.
      And I believe Mike Munkasey went into the overall issue of different systems for different applications in his “Astrological Thesaurus: Volume I”.

      But I’m also guessing you already know about all of those sources. 😉

      – Ed

  • I just can’t help quoting the astrologer/physicist William Keepin – “In my view, astrology is actually much more profound than any process that takes place in the physical realm.” Dr. Keepin is referring to implicate order (the process level) and the nature of reality. As above, so below. Is it not possible that the reason western astrology works any where in the world (regardless of an individuals DNA) , is that the easy correlation to the manifest seasonal expression was just one expression of something much more profound and universal? This way, the system works whether cherry blossoms are blooming in April or not. What would happen if we used a different language to describe this system, one that did not take away from the original meaning of the houses or the signs and rulersips but was not so insistent on crocus popping through the snow in March and leaves dying in November? It seems that perhaps we are evolving beyond the limited analogy to the seasons regardless of how counter intuitive that seems in some parts of the world, and are now forced to realize a more profound implication – to adjust our point of manifest reference relected in our language. We do not live in that ancient context – but we can take what works from the past and get a bigger perspective. We are evolving! The fact remains that astrology works, we all know this; Australians know this, Los Angeles know this – I would say that is pudding wherein lies the proof .

  • I agree Mike Wackford does a good job in making a case for Placidus at high latitudes. But its a purely theoretical/mathematical case he is making. On a practical astrological basis you couldn’t possibly construct viable charts at that latitude with Placidus. But at such an extreme polar latitude its not just a particular house system that fails. Is horoscopic astrology as we understand it that cannot cope with an MC under the earth and signs that never rise at all. Just like humans astrology didn’t evolve to exist in such extreme natural conditions.

    • Yes, but most objections to quadrant systems at extreme latitudes are also formal/theoretical, and based on flimsy arguments. So Wackford shows that there really isn’t much in the way of formal restrictions. The real trick is application. How different is that from the issues of mathematical models with “chaos” (eg discontinuities) built into them? I don’t have any easy solutions.

      • Ed , I think the astrological objections to a particular house systems depend very much on the astrologer. For the more pragmatic amongst us the objection can be as simple as that a particular system makes delineation unrealistic. For example, I live at a latitude of 55N and tens of millions of people live further north than that. Yet even at my latitude Campanus house cusps become folded in on each other to such an extent you cannot work with them. I personally, use Whole sign houses as my principal tool and prefer them to quadrant systems for natal work in working out house placement/rulership. I dont like the extremely squashed/expanded nature of houses in Placidus or Regiomontanus at my latitude. But I fully accept that is largely a matter of taste on my part. You can certainly argue Placidus is accurately reflecting the changes to ascensional rising times of the tropical signs as you travel north. I suppose my question is whether our house size should be about ascensional rising times in the first place? I think there are good arguments on both sides. Its true whole sign or equal systems are are more theorized and present a more symmetrical, neat division that isn’t necessarily reflected in nature if we go by the ascensional rising times. Also the time based systems reflect an ancient attitude focused on timing the passage of constellations that goes back to the Egyptian decans. Placidus also exactly matches the planetary hours. In contrast though you can argue a house, like a sign should reflect the 30 degree movement of the Sun and planets along the ecliptic. Its all a question of preferred symbolism isn’t it? And of course one can still use whole sign in combination with quadrant systems so it doesn’t have to be a polarized debate. I doubt any experienced astrologer would seek to deny the power and importance of the MC in a chart so I find a quadrant system like Porphyry useful to assess how effective a planet might be. I like to compare this issue to aspects. Most astrologers only use conventional aspects by degrees along the ecliptic. In that instance then astrologers seem to favour a rationalized, cosmic approach that doesn’t reflect geocentric reality. Very few use mundane or in mundo aspects that reflect where the planets really are in relation to the earth. Yet that can be a very useful approach too.

        • No argument, Mark. I was only pointing out that the extreme latitude issue has a few more dimensions than “it doesn’t work”.
          I tend to look at house issues, at least for timing and strength, only using mundo positions. For topical applications, yeah I play with whole sign houses.
          Thanks for the thoughtful commentary!
          – Ed

          • Ed, I cannot reproduce the chart in the example for 75 degrees north (Part 1), so without sufficient information as to how the house system is actually constructed, Michael Wackford’s article is inconclusive. Also, there are a limited number of houses systems discussed, and Alcabitus is not one of them. However, your discussion with Mark raises some interesting points which I am seeking to understand.
            Chris, is this discussion of house systems off topic?

          • Hi Kenneth,
            I have to admit it’s been a few years since I’ve looked at the series of articles. In principle, mundo (house) positions would be determined using standard Placidus methods unless they do not rise or set, at which point his 6-part division of the declination circle in which they are moving would be used to determine position.
            Without the details of the example in front of me, you could probably get a reasonably good graphic and list of “house positions” using the Astrodienst Fixed Star format in their Extended Chart Calculations page. The default for that format is Placidus, but I think you can also select other systems including Alcabitus.

            Yeah, we’re probably getting off-topic.

            – ed

          • Maybe we should take our houses discussion over to the podcast Chris recently did on house systems. Chris forgot to raise that topic with Deborah Houlding in their discussion on the history of house systems so I guess its a useful addition. But then again that was a discussion mostly about the historical evidence over practical delineation. You have a point Kenneth that Alcabitius produces less shrunken/swollen houses than Placidus or Regiomontanus. I know two traditional astrologers in Sweden and they both use Alcabitius semi-arc. Although Placidus, Alcabitius and Koch are all described as ‘time based’ systems they differ in how they calculate semi-arcs. Placidus, Alcabitius, & Koch involve associating the angles with the Ascendant and Midheaven and dividing by three the time taken for the degree of the Ascendant to move to the Midheaven, to find the intermediate cusps. The fundamental differences lie in the way these projections are related to the ecliptic, by use of hour circles (Placidus), vertical circles (Alcabitius), or projection of the Ascendant (Koch).

  • Ed,
    FYI, I am not able to use the Astrodienst site to produce anything reasonable in relation to the Michael Wackford’s article. One is confined to their location database, and initially I could not enter any Greenland location without the site generating a chart for Greenland Station, NH in the USA. After contacting their webmaster, they suggested I use ,GRNL and then I was able to select Nordgronland, Greenland which is 84 degrees north. The resultant chart displayed uses Porphyry with houses, but when I forced the use of Placidus in the Extended Chart Selection options, the chart had no houses at all. If I use the Pullen/Astrolog chart the display is forced into equal houses. Using a variety of application software, it’s clear that some programmers are seemingly using different calculations, or limits, for various house systems.
    Starfisher (based on Astrolog) seems to produce a more profound effect with the MC (using Nordgronland) but never drops below the horizon.
    Mark, thanks for an excellent simple explanation of the fundamental differences in the 3 mentioned house systems.

    • HI Kenneth,
      My bad. The astrodienst format does not use Wackford’s approach, but simply cuts the house division lines when points enter the zones where they neither rise nor set . I didn’t explain very well. I tried the Nordgronland location for jan 1 2016 at 6am, explicitly selected Placidus, and did get them displayed, along with the planets’ house positions in the table at the lower left of the chart. Probably the effect you’re seeing is due to the specific date/time?

      Yes, programmers will use different limits and so on. For instance, when I was programming my app that uses a Placidus like formulation, the formula given in the reference blows up due to an intermediate calculation of a trig function going out of range. By substituting a mathematically equivalent formula, the effect is avoided. So, there can be a lot of different reasons for different approaches. In my opinion, most of the differences seem to be due to differing opinions of how it ought to be done. For instance, Placidus, Topocentric and Svarogich are three different mathematical (and geometric) variants of Placidus. When calculating cusps and more importantly, mundane positions of points, there are two approaches for Placidus: Wackford’s and “give up because we’re not sure what should happen for points that don’t rise and set”. Astrodienst has chosen the latter out of agnosticism. For Topocentric, Polich and Page performed some unfounded mathematical trickery. Svarogich maintained the same formulation as for normal points on the sphere, but points out that there are sometimes three solutions to the formula for mundane positions, and one needs to look at them to decide which makes sense in a given situation.

      And that’s just for Placidus systems!

      Wackford does go into some of the related issues like reversed order signs, differing interpretation of how the MC should be defined (ie S/N vs above/below), etc.

      Anyway, it’s all interesting.

      – Ed

      • Hi Ed;
        I guess one has to be really on top of the game here and given the variation with different house implementations, the question of which house system to use becomes, to some extent, even more complicated. I haven’t programmed since the 70’s but I have interacted with some programmers over Asc/MC issues.
        For Nordgronland, I was using Wackford’s date and time (6/21/2001 00hr), on Astrodienst.–I think they have some cache issues as well because if you go back and forth with changed settings/data, some strange things start to happen. With Starfisher, I’m able to animate the time to see how the MC is affected during a 24 hour period, using the 75N00 00W00 coordinates.
        Because I was born and lived half my life in England, Placidus and Koch made no sense, and until I discovered Alcabitus, I relied on equal house charts! I’m open to using the best system available, but analyzing the data does take some time.
        As you say, this is very interesting, and thanks to you and Mark for enlightening me further.

        • Hi Kenneth,

          Most of the math issues aren’t until you get up to latitudes at the polar circle, thankfully. That’s where it starts getting a bit “esoteric” 😉
          I’m definitely going to have to check out Starfisher – sounds like a great tool!
          And thanks for the additional info on the case you looked at.

          – Ed

  • Hi Ed,
    Starfisher is available at http://www.starfisher.cz/starfisher/EN/index.htm
    The source code is available too (C++ source code)
    For the general user, I’d recommend checking out the help file as the interface is a bit different due to the way it uses objects.
    I actually contributed the font and interpretive texts for this [free] program, which the latter needs to be activated through the settings.
    I’ve even had this program running under Wine/Kubuntu, although there are a couple of bug reports on the Wine bug list site!

  • In favor of the tropical zodiac, we have… the Bible.

    Religious events/celebrations often follow the sun calendar : the birth of Jesus, the resurrection, the ascension and so.

  • Another great show well done Chris. It would have been interesting to have had Ken Bowser on the show for the Western Sidereal perspective an opportunity lost I think?

  • We know have the technology to use the real (Visual) constellations as the backdrop for a more accurate astrology based on the 13 sign constellations. I would suggest Athen’s web site mastering the zodiac for a fuller explanation of what astrologers should focus on?

  • Sidereal AStrology should never be termed as Vedic Astrology. Sidereal Astrology developed in ancient Iraq. Vedic astrology is a wrong concept altogether and Indian astrology is right word. Indian Astrology never used the zodiac but the constellation (nakshatras) and other concepts. It is a different astrology altogether like Chinese, Maya, Egyptian and Celtic. Somewhere in 4th Century, some Indian astrologers started using the zodiac. but that was very limited. Since, the influence was Greek, I think the first Indian zodiac astrologers were using Tropical. Ancient Indians hardly remembered birthdates. So, zodiac was not at all popular. Even, nakshatra (constellation) was only a literary work and not put into use. Recently (last 50 years), the zodiac has made an impression in India. Even, when I was young, astrology meant palm reading. Since, Nakshatra astrology became popular in last 80- 90 years, the sidereal calculation was also applied to zodiac.

    Many astrologers in India use the word Vedic astrology only to play the emotional game with other Indians. The reason is purely monetary.

    Regarding Sidereal vs Tropical debate, I am still confused and is still open to interpretations.

  • Great talk as well. The reason the zodiac works in both hemispheres is due to the relationship of the zodiac signs to the chakras and how the movement​ of the Sun relates to those energetic activations within our bodies at certain times during the Sun’s perceived course. This will be true no matter the hemisphere.

  • Only just found these – so donkey years 2 late to leave a topical comment. These podcasts are really interesting, I am slowly ploughing my way through them. Nice work Chris and Team.

    I would like to add:
    The Calendar Reform Committee (CRC) book is about as a PDF – search for Lahiri History of the Calendar PDF. Also: Lahiri was not chairman of the CRC, merely its secretary. He also printed a fairly popular ephemeris in India (so no vested interests in having his ayanamsa being right). He was by all accounts an astrologer himself.

    There is no historical use of using Chitra (Spica) as reference star to define degree zero of the Zodiac.

    The constellations are indeed of unequal size, but where were their original boundaries? Like the boarders of countries, did these not shift over the ages. Perhaps the lower section of Orphiuchus was originally part of Scopius? Modern constellations probably bear little resemblance to the ancient view of the skies. Perhaps it was just convenient to divide the zodiac into equal12 segments.

    Precession is not constant – so that puts a whole new slant on nutation calculation, nicely pointed out by Kenneth.

    I’m pretty sure Hipparcos did not discover precession, merely popularised it – the work had been done some 200 years prior to him, by another Greek. Weirdly Hipparcos used Chitra as one of his important starts to measure precession, he placed it at roughly 183 degrees longitude, 3 degrees different to the popular Lahiri ayanamsa.

    There are many Ayanamsa used in India. The range Kenneth gives is very conservative. Some are much larger ie: more than 3 degrees different.
    Indian astrologers I was able to speak with either don’t like Lahiri or use more traditional values. Prior to Lahiri the most popular ayanamsa in India was Revatipaksha. Its a big mystery why we called Chitrapaksha, the Lahiri Ayanamsa.
    The fact its named after a secretary should be an important clue 🙂

    • Do you have a citation or a reference I could follow up on for the statement about a Greek prior to Hipparchus discovering precession?

      • Never heard of a Greek source for precession before Hipparchus. And I have read very widely on this topic. However, there has always been a dissenting view that the Babylonians first discovered precession. http://adsabs.harvard.edu/full/1927JRASC..21..215. However, the idea has been out of favour with academics for a long time.
        https://www.jstor.org/stable/595428?seq=1#page_scan_tab_contents. In particular Otto Neugebauer was the most prominent researcher who sought to refute the theory of a Babylonian discovery of precession. .

        • Thank you for the link Mark, I will read. I’d not come across the Babylonian theory/idea before. They were pretty smart so its possible they’d figured out precession, they had after all figured out lunar nodal precession, so its not a huge leap to consider the possibility they had noted the subtle shift in earths orbit. I revisited the previous comment I’d made on Hipparchus, recalling his use of astronomical data from Timocharis but wrongly assuming the former had noted the same phenomena – apologies for that. That being said its quite amazing to think that data from Timocharis was accurate enough to make his (Hipparchus) latter comparative observation and to then formulate the idea that earths orbit was not stable. While I note precession is commonly referred to as a wobble, I see it more in terms of orbits sliding backward over time.

      • Hi Chris, quick reply. Sorry if my previous comments came over sounding pedantic, I was meaning to re-write and tone down. I get flappy about ayanamsa as I spent quite a bit of time trying to get to the bottom of that particular issue.
        In researching I came across a book called The History of Ptolemy’s Star Catalogue by Gerd Graßhoff, I am sure the reference you want in there someplace. There is a section on Hipparchus. I wrote a short précis on this:
        Taking stellar measurements from an historical astronomer Timocharis (app: 290 BCE), Hipparchus noted that Spica (α Virginis) had increased by 2º in longitude between the his own era and that of Timocharis. The former astronomer took his measurements from a total lunar eclipse placing the sun exactly 180º in opposition to the moon on the ecliptic.
        Does that help? I assumed the author to be reasonable, it seemed well researched.
        BTW – these are excellent podcasts, really professional. You’ve really put heart and soul into these. Thanks!

  • Thank you so much for this wonderful discussion. I have been thinking about this a great deal lately and stumbled over this episode by accident. So happy I did!