Okay, third time lucky. Now that Ray has told me how to delete posts
via Google, I have tried to clean up the line breaks in the last post
and removed *two* previous posts.
On Apr 21, 1:45 pm, "
x...@sympatico.ca" <
x...@sympatico.ca> wrote
[AMENDED #2]:
The following is written in ASCII maths. The general idea is that
given any point (which rises and sets), one wants to know how far it
is has gone its travel between the meridian and horizon, expressed as
a proportion of the entire time of travelling between them.
A = RAMC or sidereal time expressed as degrees
B = geographic latitude of birthplace
a = a planet's right ascension (in degrees for this formula)
d = the planet's declination
s = the sign of the planet's altitude, +1 if above the horizon, -1 if
below
The latter must be calculated not approximated, especially with bodies
like the Moon or Pluto when they are near the horizon.
Q = arccos (-tan d * (tan B))
Then the "Placidian domitude" p of the planet, expressed from 0 to 360
degrees, is
p = 90*(s + 1) + (180*[ a - A + s*Q ] ) / [ 2*s*Q ]
Note: the square brackets indicate reduction modulo 360 and this
operation has priority: it must be done immediately following the
operations inside the brackets and before the multiplication and
division outside the brackets.
The Ascendant, with ecliptic latitude 0 of course, will give p = 0;
the second Placidian cusp will give p = 30, and so on.
Naturally this convention follows conventional house systems which are
numbered Zodiac-wise rather than according to diurnal motion. This
means that planets move backwards. A planet with p = 160 is 1/3 of the
way from beng on the curve of cusp VI to lying on the western horizon
in terms of frozen zodiacal space; but actually it has travelled 2/3
of the way from the horizon to cusp VI. In their diurnal movement
planets go clockwise.
The Gauquelins made it easier to relate numbers to physical reality by
counting their positions clockwise. Let the Gauquelin sector position
be g; then g = -p modulo 360.
Whether you choose to use p or g, the advantage of reducing diurnal
positions to a 360-degree scale is that you can have any number of
sectors you want. If only eight, let them go from 0 to 45, 45 to 90,
90 to 135, and so on. If you want 18 sectors, they will go from 0 to
20, 20 to 40, etc.
PS - The forumula is indeterminate in the rare case that a planet's
altitude is exactly 0. You can easily program a fudge to determine
whether its p should be 0 or 180.