Calculations for Midheaven/Ascendant

[Sean M. Foley]

I'm rather new to astrology and was wondering someone can either
answer a few questions for me. I've read a few "Modern" astrological
books and some of the correspondences don't jive with my internal
barometer, but I've been starting move more toward traditional
astrology (i.e. Lilly, etc..) and for my purposes it seems more
useful. I've learned how to calculate charts according to Placidus
houses, but I am more interested now in Regiomontanus houses and I am
lacking critical information and I am not sure which information I am
lacking. Obviously, there is a problem in researching the
Regiomontanus houses in that I simply haven't been able to find
accurate math in computing the midheaven/asc which effects the rest of
the houses. I'm not adverse to complex math ( I will learn what I
don't know ), but not having accurate formulas to compute the core
information is making what I know of the rest of it completely
worthless. (I know how to compute charts by hand, get the ST of birth,
use ephemerides.. etc.. ) If any of the more adept can answer I would
greatly appreciate it.

- Sean

[Ray Murphy]

----------

Post by Sean M. Foley
I'm rather new to astrology and was wondering someone can either
answer a few questions for me. I've read a few "Modern" astrological
books and some of the correspondences don't jive with my internal
barometer, but I've been starting move more toward traditional
astrology (i.e. Lilly, etc..) and for my purposes it seems more
useful. I've learned how to calculate charts according to Placidus
houses, but I am more interested now in Regiomontanus houses and I am
lacking critical information and I am not sure which information I am
lacking. Obviously, there is a problem in researching the
Regiomontanus houses in that I simply haven't been able to find
accurate math in computing the midheaven/asc which effects the rest of
the houses. I'm not adverse to complex math ( I will learn what I
don't know ), but not having accurate formulas to compute the core
information is making what I know of the rest of it completely
worthless. (I know how to compute charts by hand, get the ST of birth,
use ephemerides.. etc.. ) If any of the more adept can answer I would
greatly appreciate it.
- Sean

RM: I'm not able to answer much of your question, but I think I can
help you to gain an appreciation of the formulae which other posters
will no doubt supply.

First of all you would know that the MC is the zodiac degree which is
derived from the Local Sidereal Time. This LST can be represented as
degrees of Right Ascension (RAMC) if we multiply the HMS by 15. It is
shown in all Tables of Houses, and presumably you have at least one
version.
The conversion from RAMC to a zodiac degree has a simple formula.

Now you would also know that the Ascendant is approximately 90 degrees
away from the MC, but it wanders all over the place according to the
birth latitude.

Here's a simple way to get a handle on the Ascendant: It is RAMC + 90
degrees + Ascensional Difference (where the Ascensional Difference
can be positive or negative).
The Ascensional Difference can be calculated by first obtaining the
Declination.

Let's say we calculated the Ascensional Difference for a particulat
time and latitude and got -10 degrees. This means that the OA (Oblique
Ascension) of the Ascendant = RAMC + 90 + (-10). When we add those
three together we then have to convert the resulting answer to a
degree of the zodiac again which is the Ascendant degree.

You may want to bypass this information entirely and go straight to
modern formulae, but I found that it gave me a ~slight~ understanding
of what's going on with the Ascendant at least.
I haven't got a clue how to calculate the other cusps by hand.

Ray

[Chris Mitchell]

Post by Sean M. Foley
I'm rather new to astrology and was wondering someone can either
answer a few questions for me. I've read a few "Modern" astrological
books and some of the correspondences don't jive with my internal
barometer, but I've been starting move more toward traditional
astrology (i.e. Lilly, etc..) and for my purposes it seems more
useful. I've learned how to calculate charts according to Placidus
houses, but I am more interested now in Regiomontanus houses and I am
lacking critical information and I am not sure which information I am
lacking. Obviously, there is a problem in researching the
Regiomontanus houses in that I simply haven't been able to find
accurate math in computing the midheaven/asc which effects the rest of
the houses. I'm not adverse to complex math ( I will learn what I
don't know ), but not having accurate formulas to compute the core
information is making what I know of the rest of it completely
worthless. (I know how to compute charts by hand, get the ST of birth,
use ephemerides.. etc.. ) If any of the more adept can answer I would
greatly appreciate it.
- Sean

Hi, Sean -

I see Ray's given some very helpful guidelines. I don't have much to
add except to say I've got a PDF document that was someone's research
project (published on the web) which gives a brief overview of some of
the house systems. It has this to say about Regiomontanus:

"The celestial equator is first divided into twelve equal parts, each
of 30°. These twelve points are then projected onto
the ecliptic along great circles which start at the north point of the
horizon. The intersection of these circles with the ecliptic determine
the cusps of the houses."

Together with a nice little diagram illustrating it. If you or anyone
else wants a copy, drop me an e-mail (chrismitchell at zaalberg dot
freeserve dot co dot uk) and I'll e-mail it to you.

As far as the algorithms are concerned, the source code for Astrolog
is freely available - file matrix.c has the algorithm for Astrolog's
house cusp calculations. Have a look at
http://www.astrolog.org/astrolog/astfile.htm for details.

[Sean M. Foley]

Post by Chris Mitchell
Together with a nice little diagram illustrating it. If you or anyone
else wants a copy, drop me an e-mail (chrismitchell at zaalberg dot
freeserve dot co dot uk) and I'll e-mail it to you.
As far as the algorithms are concerned, the source code for Astrolog
is freely available - file matrix.c has the algorithm

As luck would have it, I found this awesome information on the web.
I'd recommend ANYONE that cares about such things to give the
following link a read.

http://geocosmic.org/articles/astrohouse.php?fileref=includes/housemain.shtml#overview

Calculation, definitions of terms used, etc. for over 20 house
systems. Do houses on a calculator! :) Hopefully this helps someone
beside me. I am not much for the AFA or NCGR, but this is excellent
information. :)

- Sean

[Chris Mitchell]

Post by Sean M. Foley
As luck would have it, I found this awesome information on the web.
I'd recommend ANYONE that cares about such things to give the
following link a read.
http://geocosmic.org/articles/astrohouse.php?fileref=includes/housemain.shtml#overview
Calculation, definitions of terms used, etc. for over 20 house
systems. Do houses on a calculator! :) Hopefully this helps someone
beside me. I am not much for the AFA or NCGR, but this is excellent
information. :)
- Sean

Sean - thank you so much for posting that! I've been looking for a
site like that for ages :)

Chris.

[Ed Falis]

On Wed, 28 Apr 2004 18:04:44 CST, Sean M. Foley

Post by Sean M. Foley
As luck would have it, I found this awesome information on the web.
I'd recommend ANYONE that cares about such things to give the
following link a read.
http://geocosmic.org/articles/astrohouse.php?fileref=includes/housemain.shtml#overview

It's really hard to beat Mike Munkasey on this topic - he's put a lot into
it. Great find!

- Ed

[Martin Lewicki]

Post by Sean M. Foley
As luck would have it, I found this awesome information on the web.
I'd recommend ANYONE that cares about such things to give the
following link a read.
http://geocosmic.org/articles/astrohouse.php?fileref=includes/housemain
.shtml#overview

Well..say no more... :)

Martin

[Martin Lewicki]

Post by Sean M. Foley
I'm rather new to astrology and was wondering someone can either
answer a few questions for me. I've read a few "Modern" astrological
books and some of the correspondences don't jive with my internal
barometer, but I've been starting move more toward traditional
astrology (i.e. Lilly, etc..) and for my purposes it seems more
useful. I've learned how to calculate charts according to Placidus
houses, but I am more interested now in Regiomontanus houses and I am
lacking critical information and I am not sure which information I am
lacking. Obviously, there is a problem in researching the
Regiomontanus houses in that I simply haven't been able to find
accurate math in computing the midheaven/asc which effects the rest of
the houses. I'm not adverse to complex math ( I will learn what I
don't know ), but not having accurate formulas to compute the core
information is making what I know of the rest of it completely
worthless. (I know how to compute charts by hand, get the ST of birth,
use ephemerides.. etc.. ) If any of the more adept can answer I would
greatly appreciate it.
- Sean
From Recent Advances - G.Dean (1976)

Regiomontanus House Cusps

Longitude of cusp = arctan(tan(D)cos(C+E))

where C = arctan(tan(arcsin(sin(L)sin(H)))/cos(D))
D = RAMC+90-arctan(cos(H)/(sin(H)cos(L)))

For
cusp 11: H=30
cusp 12: H=60
cusp 2: H=120
cusp 3: H=150

Hope I got all the bracket expression correct.

Martin

[Ed Falis]

Post by Martin Lewicki
Hope I got all the bracket expression correct.

Only problem is those are the formulae for the Campanus cusps :-(

I almost made the same mistake last night when copying in the Regio ones
just below there. For some reason, my posts on this subject have not made
it to the newsgroup, so you might want to wait a bit rather than have to
type them in again.

- Ed

[Ed Falis]

Sean,

The ascendant is the same for most house systems, as is the MC (which is
not the tenth house cusp in equal house systems). Regiomontanus has the
same ASC and MC as Placidus, Campanus, Koch etc.

Longitude of cusp = arctan (cos (R) * tan (RAMC + H)/ cos (R + E))

where:

R = arctan (sin (H) * tan (L) / cos (RAMC + H)

For cusps:

10 (MC): H = 0
11: H = 30
12: H = 60
1 : H = 90
2 : H = 120
3 : H = 150

and:

E: obliquity of the ecliptic for the date (23.4523 in 1900; 23.4393 in
2000)
L: geographic latitude
RAMC: right ascension of MC = 15 * local sidereal time

All from Dean and Mather "Recent Advances in Natal Astrology"

- Ed

[Ed Falis]

On Tue, 27 Apr 2004 19:46:41 CST, Sean M. Foley

... I've learned how to calculate charts according to Placidus
houses, but I am more interested now in Regiomontanus houses and I am
lacking critical information and I am not sure which information I am
lacking.

Mike Munkasey has a book out (that includes formulae for a lot of house
systems), and which has some opinions on which are good for what. You
might try to track it down. The title may have been something like "An
Astrological Thesaurus, Vol 1: the Houses".
At least that can give you some perspective on the house division issue.

It helps to know what problem(s) various house systems try to solve.
Placidus, Campanus and Regiomontanus were attempts to provide a basis for
the use of Ptolemy's version of primary directions. The Topocentric
system is just a different mathematical formulation of system described by
the Placidus method. Koch is different as it doesn't address the same
issues as these others - which is fairly typical of house systems invented
in the 20th century. Then there are the various "equal house" methods
that address a different problem space - I think that Robert Schmidt of
Project Hindsight nailed the difference between the quadrant systems
(those mentioned above) and the equal division systems really well in an
article he has somewhere on the net: timing and strength of planets (in
the quadrant systems) vs topical classification of influences (in the
equal house systems). Deborah Houlding's "The Houses - Temples in the
Sky" explores the historical basis of the latter use of houses, and
complements Schmidt's article nicely.

Have fun!

;-)

- Ed

[Ed Falis]

OK, I was confused. Here's a still-worthwhile article by Robert Schmidt
http://av.rds.yahoo.com/_ylt=ApPOuj_kpVsIwmhRjs70cw6DBqMX;_ylu=X3oDMTBwMjNqdWVsBHBndANhdHdfd2ViX3Jlc3VsdARzZWMDc3I-/SIG=11b62hir6/**http%3a//cura.free.fr/quinq/02schmi.html

And somewhere out there is an article by Robert Hand on the same subject
that may have been the one I was thinking of.

- Ed

[KathrynK]

Obviously, there is a problem in researching the

Post by Sean M. Foley
Regiomontanus houses in that I simply haven't been able to find
accurate math in computing the midheaven/asc which effects the rest of
the houses.

If you go onto the astrodeinst site online, it can draw up a regiomantanus
chart for you for free.
Some people feel they have to do it by hand though. I'm not a purist like
that; I'd rather spend my time interpreting charts than drawing them up:)
Love
Kathxxxxx

[Sean M. Foley]

Post by Sean M. Foley
Obviously, there is a problem in researching the

Post by Sean M. Foley
Regiomontanus houses in that I simply haven't been able to find
accurate math in computing the midheaven/asc which effects the rest of
the houses.

If you go onto the astrodeinst site online, it can draw up a regiomantanus
chart for you for free.
Some people feel they have to do it by hand though. I'm not a purist like
that; I'd rather spend my time interpreting charts than drawing them up:)
Love
Kathxxxxx

For the most part I see myself doing this as well, however I do not
blatantly trust such things and would like to know enough to be able
to validate any computer programs results. If you have the right kind
of calculator (I do) you can pre-program the equations into it and
calculate all the houses with it right off of the Sidereal Time
(almost like using the computer, but.. portable).

-Sean

[Alois Treindl]

Post by Sean M. Foley
Obviously, there is a problem in researching the

Post by Sean M. Foley
Regiomontanus houses in that I simply haven't been able to find
accurate math in computing the midheaven/asc which effects the rest of
the houses.

If you go onto the astrodeinst site online, it can draw up a regiomantanus
chart for you for free.

You can also find the Swiss Ephemeris source code for house calculations
at ftp://ftp.astro.com/pub/swisseph/src/
file swehouse.c

and some information on the various house systems at
http://www.astro.com/swisseph/swisseph.htm#_Toc6813693

Our source code has the advantage that is is quite stable, i.e. tries to
deal carefully with special cases where tan(x) can get infinite, etc.