skyscript.co.uk
   

home articles forum events
glossary horary quiz consultations links more

Read this before using the forum
Register
FAQ
Search
View memberlist
View/edit your user profile
Log in to check your private messages
Log in
Recent additions:
Can assassinations be prevented? by Elsbeth Ebertin
translated by Jenn Zahrt PhD
A Guide to Interpreting The Great American Eclipse
by Wade Caves
The Astrology of Depression
by Judith Hill
Understanding the mean conjunctions of the Jupiter-Saturn cycle
by Benjamin Dykes
Understanding the zodiac: and why there really ARE 12 signs of the zodiac, not 13
by Deborah Houlding

Skyscript Astrology Forum

Placidus houses

 
Post new topic   Reply to topic    Forum Index -> Nativities & General Astrology
View previous topic :: View next topic  
Author Message
Donald



Joined: 07 Sep 2018
Posts: 6

Posted: Mon Sep 10, 2018 1:46 pm    Post subject: Placidus houses Reply with quote

I hope someone out there can answer a question for me. I have read that Placidus house cusps are unique in that the diurnal semi-arc is trisected so cusps 12, 11, and 10 are 1/3, 2/3 and 3/3 along " their own diurnal semi-arc," as opposed to say, alcabatius, that trisects the ascendant semi-arc. What is the advantage of this? Is Placidus a better representation of the sky at the moment in question? Thanks.
Back to top
View user's profile Send private message
james_m



Joined: 05 Dec 2011
Posts: 3621
Location: vancouver island

Posted: Mon Sep 10, 2018 5:32 pm    Post subject: Reply with quote

hi donald - welcome to skyscript.. skyscript is broken up into different forums.. you've posted this in the philosophical forum where you are unlikely to get the technical question you ask, addressed... it would be better to address this in the general astrology forum.. cheers james
Back to top
View user's profile Send private message
Paul
Administrator


Joined: 23 Nov 2009
Posts: 1535

Posted: Mon Sep 10, 2018 6:13 pm    Post subject: Reply with quote

That's actually my fault James - I thought I moved it here (from the traditional forum), I pressed the wrong forum!
_________________
"The only true wisdom is in knowing you know nothing" - Socrates

https://heavenlysphere.com/
Back to top
View user's profile Send private message
james_m



Joined: 05 Dec 2011
Posts: 3621
Location: vancouver island

Posted: Mon Sep 10, 2018 7:17 pm    Post subject: Reply with quote

lol! easy enough mistake to make!
Back to top
View user's profile Send private message
Ruud66



Joined: 05 Apr 2009
Posts: 51
Location: Amsterdam, Netherlands

Posted: Tue Sep 11, 2018 6:39 am    Post subject: Re: Placidus houses Reply with quote

Donald wrote:
I hope someone out there can answer a question for me. I have read that Placidus house cusps are unique in that the diurnal semi-arc is trisected so cusps 12, 11, and 10 are 1/3, 2/3 and 3/3 along " their own diurnal semi-arc," as opposed to say, alcabatius, that trisects the ascendant semi-arc. What is the advantage of this? Is Placidus a better representation of the sky at the moment in question? Thanks.

Hello Donald,
That's actually a very good question. I think many astrologers will give you a different answer, each from their own frame of reference and experience as an astrologer. So any attempt of answering this question must be done with humility, because there are no absolute answers.

My answer is: yes, Placidus houses are unique in the manner that you describe and no, that does not mean that it is better or worse than other house systems, just different.
My own take on the whole arena of house systems is that each system was formulated on a specific moment in history and each system answered a particular question, or met a specific need at that time.
Actually you could write an entire book just on this subject.

The Placidus system was developed by several astrologers/astronomers/mathematicians in the early 17th century. These people knew about the latest developments in astronomy and trigonometry and they wanted to use these insights to make real the vision of Ptolemy, at least how they interpreted that, as he described the motions of the sky in his chapter on primary directions in the Tetrabiblos.
You could say that these astrologers were fundamentalists, who wanted to take the word of God (in this case the word of Ptolemy) as litteral as possible.

As a result, a system was developed that is particularly good at describing the motions of the sky due to the rotation of the earth, the so-called Primum Mobile, or first motion of the earth (the second motion being its yearly path around the sun.)

So if you care about these astronomical elements and want to take into account the differences these astronomical elements cause in the shape of the horoscope at different latitudes, then maybe you as an astrologer will be attracted to this system. Further advantage is that quite a lot of astrologers use this system and a lot of material is published on the interpretation of the houses with the Placidus system in mind.
But does that mean that "Placidus is a better representation of the sky at the moment in question?" I'm not so sure. It depends on the things you desire to take into account when you construct your houses.
Back to top
View user's profile Send private message Send e-mail
Paul
Administrator


Joined: 23 Nov 2009
Posts: 1535

Posted: Wed Sep 12, 2018 1:22 pm    Post subject: Reply with quote

Donald

It really depends on what you’re trying to model specifically - all the house systems model something.

If you want to model something observable for example, so that you could look up into the sky and imagine roughly where the houses are, Placidus will not help you. If you’re trying to model the rising and setting of a point, fixed for a given moment in time (like birth), Placidus won’t help. If you want to model the relative movement of planets and points as they actually rise and set etc such that you can divide it up temporally evenly then Placidus excels and outshines any other house system.

But it really depends what your focus is in terms of what you want to model. Because no house system can model everything all at once with equal weight.
_________________
"The only true wisdom is in knowing you know nothing" - Socrates

https://heavenlysphere.com/
Back to top
View user's profile Send private message
Donald



Joined: 07 Sep 2018
Posts: 6

Posted: Mon Oct 14, 2019 12:44 am    Post subject: Placidus houses Reply with quote

Another question please. If Placidus cusps 12, 11, and 10 represents 1/3, 2/3 and 3/3 of the diurnal cycle for each degree on its own declination circle, does that also represent 30, 60, and 90 degrees respectively of the space from the horizon to the midheaven? That is, do Placidus cusp represent a true picture of the sky?
Back to top
View user's profile Send private message
Ruud66



Joined: 05 Apr 2009
Posts: 51
Location: Amsterdam, Netherlands

Posted: Sat Oct 19, 2019 5:31 pm    Post subject: Reply with quote

No, not 30, 60 and 90 degrees and yes, it is a true picture of the sky.

The 1/3, 2/3 and 3/3 cut-off points are 30, 60 and 90 degrees ONLY when the diurnal arc is 180 degrees. Therefore, this is only true for the equinoxes and any other point on the celestial equator. But Placidus takes all diurnal arcs into account, (and all nocturnal arcs for that matter,) not just the one that happens to be 180 degrees, so in that way it is a rendering of the true sky, seen through the lens of ascension and descension in relation to the horizon.
Back to top
View user's profile Send private message Send e-mail
Donald



Joined: 07 Sep 2018
Posts: 6

Posted: Sun Oct 20, 2019 3:46 am    Post subject: Placidus houses Reply with quote

Thanks Ruud66
Back to top
View user's profile Send private message
Donald



Joined: 07 Sep 2018
Posts: 6

Posted: Fri Nov 29, 2019 10:27 pm    Post subject: Placidus and planetary hours Reply with quote

As per Deborah Houlding's book, Placidus houses are based on the same concept as planetary hours in that each Placidus house contains 2 planetary hours. I get the idea but I have a point of confusion here since planetary hours are based on solar time (sunrise to sunset) yet Placidus houses are based on sidereal time. Am I missing something here? Anyone have any thoughts on this issue?
Back to top
View user's profile Send private message
Ruud66



Joined: 05 Apr 2009
Posts: 51
Location: Amsterdam, Netherlands

Posted: Sun Dec 01, 2019 6:58 pm    Post subject: Re: Placidus and planetary hours Reply with quote

Your understanding is correct. The principals behind the planetary hours and Placidus houses are the same, but the calculation is slightly different in the way you describe.

Both the planetary hours and the Placidus houses are calculated by dividing how much time something is above the horizon by the entire time it will spend above the horizon. Ecliptic degrees are points that do not move at all, because they are part of the tropical system itself, but the Sun is always moving and changes its declination all the time. And a change in declination results in a different diurnal arc, while ecliptic degrees have always the same declination. (The obliquity of the ecliptic changes very very slowly.)

Therefore, it is more practical to calculate the planetary hours in one way (using the rising and setting times of the Sun) and the Placidus houses in another way (using the diurnal and nocturnal arcs,) but the end result is the same.
At the start of the 5th hour of the day, for example, the Sun is exactly on the placidean cusp 11, while the rising and setting times of that same point on the ecliptic, are very slightly different from those of the Sun. Again: because the Sun is moving and the ecliptic is not.
Back to top
View user's profile Send private message Send e-mail
Donald



Joined: 07 Sep 2018
Posts: 6

Posted: Sun Dec 01, 2019 10:57 pm    Post subject: Reply with quote

Thanks, Ruud66
Back to top
View user's profile Send private message
Ruud66



Joined: 05 Apr 2009
Posts: 51
Location: Amsterdam, Netherlands

Posted: Mon Dec 02, 2019 8:44 am    Post subject: Reply with quote

Donald wrote:
Thanks, Ruud66

You're very welcome.

To expand on your original post:

The Placidus houses is just as much a compromise in the way it models the diurnal motion as all other house systems. The Placidus system focuses so much on the astronomical time cycles that it breaks all the laws of Sacred Geometry and at the core of its design it is agnostic about the ecliptic.

House systems that focus on the diurnal motion of the ecliptic itself are Whole Sign and Equal houses, and to a lesser extend Porphyry.
House systems that try to apply the rules of Sacred Geometry by using only great circles are mainly Campanus and Regiomontanus.
Most other house systems are more of a mixed bag.

As Paul is saying: "... no house system can model everything all at once with equal weight."
Back to top
View user's profile Send private message Send e-mail
Display posts from previous:   
Post new topic   Reply to topic    Forum Index -> Nativities & General Astrology All times are GMT
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
. Powered by phpBB © 2001, 2005 phpBB Group

       
Contact Deborah Houlding  | terms and conditions  
All rights on all text and images reserved. Reproduction by any means is not permitted without the express
agreement of Deborah Houlding or in the case of articles by guest astrologers, the copyright owner indictated