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Skyscript Astrology Forum

Most common way to progress the MC in longitude?
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Chris Meyer



Joined: 19 Sep 2014
Posts: 22

Posted: Fri Jul 17, 2015 5:37 am    Post subject: Reply with quote

Hi Ruud66,

really glad we agree now about that.

Thank you for sharing the other methods and for the detailed explanation of their theoretical background!

If I understand you right 'method 1' and 'method 2' are the same as mine. And 'method 3' (meanwhile added to my initial post) is my formerly wrong written 'method 2'. When I realized that I had written 'method 2' wrong, I already asked myself if this could be another way to progress/direct the MC.

In an another article on his website titled "A Correction on the Solar Arc Key in Primary Directions" Wim van Dam introduced a corrected method of his system: http://www.astrosoftware.com/WimSolarArcKey.htm

To my ears this corrected formula sounds far more complicated than his old one:

1. Convert the sunís radical position in the houses to its mundane longitude
2. Subtract the sunís radical regular zodiacal position from the one on the actual date
3. Add this arc to the result of (1). This gives the sunís desired mundane position.
4. Calculate the GMT on the secondary day for the moment when the actual sun will have a mundane longitude equal to the result of (3)
5. For this GMT on this secondary date, calculate the sunís zodiacal position
6. Subtract from this the sunís radical longitude and
7. Add this arc to the radical MC.

I'd tried hard to program it. But unfortunately van Dam gave no example calculations of his new corrected method. So I found no way to verify my results. Maybe you know where to find example calculation results or can provide it? Or do you know a simpler formular to program his corrected method?
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Ruud66



Joined: 05 Apr 2009
Posts: 35
Location: Amsterdam, Netherlands

Posted: Mon Jul 20, 2015 9:15 am    Post subject: Reply with quote

Chris Meyer wrote:
To my ears this corrected formula sounds far more complicated than his old one:

1. Convert the sunís radical position in the houses to its mundane longitude
2. Subtract the sunís radical regular zodiacal position from the one on the actual date
3. Add this arc to the result of (1). This gives the sunís desired mundane position.
4. Calculate the GMT on the secondary day for the moment when the actual sun will have a mundane longitude equal to the result of (3)
5. For this GMT on this secondary date, calculate the sunís zodiacal position
6. Subtract from this the sunís radical longitude and
7. Add this arc to the radical MC.

Thanks for this link to Wim van Dam's recent work.
I learned about Van Dam's primary progressions in astrology class with Karen Hamaker-Zondag. She is very supportive of this particular method of primary pogressions and she has worked with it for decades getting good results from it. She even wrote a textbook about it explaining her method of combining transits, secondary progressions and these primary progressions. (In Dutch: "Handleiding voorspellende astrologie"). I didn't read this book yet, however, so can't say anything about it.

There is one thing I always do when I discover a new method of doing anything at all in astrology, like a new house system, or a new method of progressions/directions: I test such a method in extreme circumstances. Usually this means I test how such a method or system works in the arctic latitudes.
I do this because I believe that good astrological techniques should have a consistency all over the globe and not break down in the arctic, for example. If a system does break down somewhere, then you can't use the technique or house system for everyone or for all situations, which I consider to be a basic flaw in the technique.

Van Dam's primary progressions are impossible in the arctic, because he refers the progressed planets back to the ecliptic using placidean hous curves. On arctic latitudes the hous curve that a planet is on sometimes doesn't intersect the ecliptic at all, and sometimes it intersects the ecliptic multiple times. It is the same problem you get with placidus houses in the arctic, but that is a huge subject on its own.

Fortunately for Van Dam, it is not really necessary to refer the primary planets back to the ecliptic. You can simply use Van Dam's parameters in the system of Ptolemaic primary directions. In this system you work with the mundane longitudes only and do not refer back to the ecliptic.
This way of doing primary directions works wonderfully, also in the arctic.

But now this "corrected" formula for progressing the Midheaven. Here Van Dam uses once more a technique that breaks down in the arctic. He uses an element of the "French" method. You could see this French method as follows: it applies the concept of the unequal hours of the day to find out the relative position of the Sun in the secondary day. In each consecutive secondary day the moment is calculated that the Sun has the same position in mundane longitude, or in other words, the same relative house position in the placidus houses.

His old method works in the arctic, but this French method and therefore also his new corrected method does not. To illustrate this, imagine the following scenario:
Someone was born before sunrise with the Sun in late Taurus. Let's say the person was born in Murmansk. The Sun becomes circumpolar at 4į28' Gemini on the latitude of Murmansk.
Therefore a week after the person was born, the Sun will never be below the horizon anymore for about 55 days. In those days, the Sun cannot return to its natal mundane longitude. Therefore, it is technically impossible to calculate anything at all using the French method, and also not using this new corrected Van Dam method, because the method breaks down at step 4.
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Chris Meyer



Joined: 19 Sep 2014
Posts: 22

Posted: Wed Jul 22, 2015 4:01 am    Post subject: Reply with quote

Thanks for referring to Karen Hamaker-Zondag. I didn't know that she's working with Primary Directions nor that she succesfully uses van Dams method for so long.

Ruud66 wrote:
His old method works in the arctic, but this French method and therefore also his new corrected method does not. To illustrate this, imagine the following scenario:
Someone was born before sunrise with the Sun in late Taurus. Let's say the person was born in Murmansk. The Sun becomes circumpolar at 4į28' Gemini on the latitude of Murmansk.
Therefore a week after the person was born, the Sun will never be below the horizon anymore for about 55 days. In those days, the Sun cannot return to its natal mundane longitude. Therefore, it is technically impossible to calculate anything at all using the French method, and also not using this new corrected Van Dam method, because the method breaks down at step 4.

You opened my eyes. Struggling to get this method programmed I missed to reflect about that point. So only the standard van Dam Primary Directions that are most widely used and based on 'method 2' really make sense.

But to be honest I never did Primary Directions for a horoscope from Murmansk before. So far the most northern place I had worked with Primary Directions in practice was 'Ludvika' in Sweden (latitude 60n09) for the horoscope of Anna Lindt: http://www.astro.com/astro-databank/Lindh,_Anna. My preferred Placidus semiarc method worked absolutely flawless with this horoscope. But Murmansk is really a ultimative test case and I doubt that even Placidus semiarcs will give trustworthy results that match with live events for this place. Because the MC doesn't stay always above the horizont. But if it's not even possible to calculate van Dams 'corrected' method at very high latitudes then it's obviously that they don't work.

On the other hand you could say I got a nice car that drives marvelous on paved roads. That is what I used to to. But off road on rough terrain it's getting stock and doesn't work at all. But because you're aware of this it doesn't bother you. No one would come to the conclusion that therefore your car doesn't work in general. For myself I don't expect that every astrological technique has to work for all cases. I only have to know where a technique works and where not to be able to choose the right tool for a given situation. But as already said this is another topic.

Thanks again for sharing your knowledge.


Last edited by Chris Meyer on Thu Dec 03, 2015 4:46 am; edited 2 times in total
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Rogp



Joined: 29 Dec 2014
Posts: 4
Location: Freckleton, Lancashire, UK

Posted: Wed Dec 02, 2015 11:55 pm    Post subject: Re: Most common way to progress the MC in longitude? Reply with quote

Chris Meyer wrote:
Hi,

in my home country in Europe we almost exclusively progress or direct the MC on the equator in right ascension. Therefore I like to learn more about how progressing the MC in longitude is done?

Chris


Hi Chris

I'm a bit late in responding but maybe here's something to consider...

I do believe that a very common way to secondary progress the MC and Asc are the way that Astro.com calculate it. Many, many years ago I learnt this method (by hand) as taught by Margaret Hone in her book The Modern Text-Book of Astrology (I think), and may be the method still taught today by the UK Astrological Association.

It's a method I still use myself today, although progressing by RAMC has an attraction.

The astro.com method gives the following for the secondary progressed angles for 21st April 205, for Queen Elizabeth II:

Asc. Gem 24į16' 6"
MC Aqua 18į29'54"

Quite a notable difference.

Solar Fire calls this option: Mean Quotidian! And using this gives the same results as astro.com.

There's an interesting discussion here: https://groups.yahoo.com/neo/groups/swisseph/conversations/topics/1787

It's touched on here:

http://skyscript.co.uk/forums/viewtopic.php?t=7257&highlight=mean+quotidian


Another minefield! Or do we love the diversity?

Roger

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Chris Meyer



Joined: 19 Sep 2014
Posts: 22

Posted: Thu Dec 03, 2015 4:41 am    Post subject: Reply with quote

Hi Rogp,

Astrodienst (astro.com) calculates just "normal" Secondary Progressions with MC direction on the equator (in RAMC) with Naibod key. But be aware that astro.com always calculate Secondary Progressions for 0:00 UT!

As already said this is probably the most common way to calculate Secondary Progressions in Europe. In "Solar Fire" it is the option "Chart Angle Progression: Naibod in RA".

"Mean Quotidian" chart angle progression is a completely different story. They are also called "daily angle progressions". Because the MC progresses 1į per day = 360į in 1 year. Where "normal" secondary directed chart angles progressing about 1į per year.

This can easily be seen by comparing Secondary Progressions with "Mean Quotidian" chart angle progression for Queen Elizabeth on April 21, 2015 with April 30, 2015. In this short period of time the difference is already about 10į on the MC. These chart angles are not directed. They are a result of a normal horoscope calculation for the time of the secondary date.


Last edited by Chris Meyer on Thu Dec 03, 2015 11:24 am; edited 1 time in total
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Rogp



Joined: 29 Dec 2014
Posts: 4
Location: Freckleton, Lancashire, UK

Posted: Sat Dec 05, 2015 7:33 pm    Post subject: Reply with quote

Hi Chris,

Thanks for your very useful reply.

Interesting stuff.

Roger
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AloisT



Joined: 19 Oct 2011
Posts: 9
Location: Z√ľrich, Switzerland

Posted: Thu Nov 30, 2017 10:42 am    Post subject: Most common way to progress MC and Ascendant Reply with quote

This thread has come to my attention, via Google, because there are repeatedly discussions on the Astrodienst forum about how to do secondary progressions.
See https://forum.astro.com/cgi/forum.cgi?num=1511366337/24#24

In this posting I have lined out my position on the subject, which is the one implemented on www.astro.com

Further up in the thread I have also explained Astrodienst's opinion.

Quote:
What is progressed is not the Ascendant, as such. The Ascendant is only a 'derived quantity'.

What is progressed is the Sidereal Time, also called RectAscension of Medium Coeli, or RAMC or ARMC.

It is progressed with its daily rate of 3m56.5 seconds, as shown in each ephemeris in the column for 'Sidereal Time'. Technically, it represents the angle between the meridian and the vernal equinox, measured along the celestial equator.

In the ephemeris Sidereal Time is listed for midnight Universal time, at the Greenwich meridian. For an actual chart, timezone and actual meridian must of course be considered. That does not affect the rate of progression.

This progressed Sidereal Time is used to calculate the house cusps, including the Ascendant and MC of the progressed chart, just like the natal Sidereal Time is used for the birth chart.

Depending on the geographical latitude, for a given progress of RAMC, some Ascendant signs change faster (the fast rising signs) and some change slower (the slow rising signs). In the northern hemisphere, the fastest rising signs are Pisces and Aries, the slowest are Virgo and Libra.

The rule 'one day in the ephemeris corresponds to one year of life' is applied both to the planets and the sidereal time/RAMC.

There exist astrologers who apply this rule only for the planets, but chose to progress Sidereal Time with a different rule. This is why some software offers different 'keys' for progressing RAMC, while Astrodienst only uses the fixed ephemeris based rule.
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