Skyscript Astrology Forum

Hello,

Tony, I see that we have slight difference is the directed arc. I have 28? 44?, while you have 27? 49?. Where do you get your oblique ascensions from? I?m trusting that web site I cited but who know how they calculate it.

To Calculate right ascension, RA and oblique ascension, OA:-

First we need the obliquity of the ecliptic, obl

obl = 23.45229444 - [0.4684 x (year-1900)/3600]
(This is an empirical formula to calculate obliquity of the ecliptic w/o having to refer to astronomical table)

example in year 1616

obl = 23.45229444 - (0.4684 x (1616-1900)/3600)
obl=23.489246
obl = 23 deg 29 min 21.3 sec
Comparison with solar fire, obl = 23deg 29 min 21 sec

Another example (Year 2006)
Using the above formula, obl = 23.43849677 = 23 deg 26 min 18.6 sec
Comparison with solar fire, obl = 23deg 26 min 18 sec

Calculation of Right Ascension (RA):-
tan RA = tan (long) x cos (obl)
long = longitude, obl = obliquity of the ecliptic

Let us calculate the right ascension, RA of midheaven, MC in Lilly's English Merchant example,
the year was 1616,
obl (calculated above) = 23.489246 deg
longitude of the MC (given) = 14 deg 39 min Scorpio
From Aries, longitude of MC then equals to 224 deg and 39 min = 224.65 deg.

tan RA = tan (224.65) x cos (23.489246)
tan RA = 0.905997877
RA = 42.17651082 deg***
but this is in the 3rd sector (longitude is between 180 to 270 deg), hence
RA = 42.17651082 + 180 = 222.1765108 deg = 222 deg 10 min 35 sec (***see below).

Using the site that you gave the RA for longitude 224 deg 40 min (round off from 224 deg 39 min) is 222 deg 12 min.

*** if RA is greater than 0 and longitude is less than 180, leave RA as is
if RA is greater than 0 and longitude is greater than 180, add 180 to RA
if RA is less than 0 and longitude is less than 180, add 180 to RA
if RA is less than 0 and longitude is greater than 180, add 360 to RA

if longitude is 0 deg, RA = 0 deg
if longitude is 90 deg, RA = 90 deg
if longitude is 180 deg, RA = 180

Observe that place is not required to calculate RA, only year (for obliquity) and of course the corresponding degree (in this case the MC).

Next, the calculation of oblique ascension, OA

Hello Mark and others,

I don't know how to get primary directions with the Solar Fire but "Janus 3" gives it directly and very easily (just by clicking a button).

Janus allows you to choose three modes or types of directions (each primary) based on three different types of selection of LATITUDE in both direct and converse order:

1) radix (i.e based on the latitude in the natal chart)
2) directed (based on the latitude of the directed planet)
3) zero (latitude of the ecliptic is zero)

Each selection works as a reference circle.

I use;

- (1) above to direct primarily AC and MC to the planets in the natal figure as thought by Zoller (if I understood correctly), and also to direct natal planets to the angles;

- (2) to check what changes (a different date?) when the latitude of "directed" planets is taken instead of radix. It helps to see other dates or contacts which fit in astrological symbolism of the events in one's life. Often you catch some important dates/events that are missed by (1). If I'm not wrong, Zoller leaves it open for a research matter whether it is best to use (1) or (2) in his Tools and Techniques Book 2.

- (3) to direct planets to natal planets

It is also helpful to read Bob Markansky's free e-book on this topic which is also cited by R.Zoller himself in his Diploma Course material

See http://www.dearbrutus.com/ for the free pdf book on primary directions (click "book" first and proceed as said there).

Cheers,
Sigma

Hello Sigma,
I use Janus. I have always assumed that the PD's were the modern.
I am going to use all three ways you have listed and compare to my "hand" calculations. This is exciting!
I could kiss both Mark (for bringing this up)
and you for using JANUS!!!!!

Peaches!!!!! both of ya.

I'll get BACK with ya'll. Top Priority..........If Janus does do it by zoller's method's it will save me DAYS of work.
......singing in the rain

thanks!!!!!!!!!!!!!!!!!!!!!!!!
~she

In the post concerning the mystery chart Tom points out that Solar Fire seems to calculate primary directions using mundo primaries. I learned to calculate basic primaries from Rumen Kolev?s booklets (available from astroamerica.com) a couple of years ago ? I recommend those booklets warmly, clear explanations, clear pictures, it seems frightening at first, but when you dwell on it, Kolev guides you by hand.

I calculated mundo directions by hand and compared my results with Solar Fire Primary Mundane Directions and they were the same. I have now a demo version of Janus 3 on my computer and I compared the directions by Janus with those of Solar Fire and the results were fairly different! I don?t know what?s the method in Janus, but it?s different from Solar Fire and from Kolev. I suppose Janus is calculating zodiacal directions?

Kolev writes:

?What the programmers of these programs and their dealers (in good faith) called primary directions had nothing to do with the real primary directions employed by Placidus, W. Lilly, Tycho de Brahe, Alan Leo, Kuehr and the other authorities on the subject. (?) But what these modules actually do, most often, is some kind of pseudo-primaries. One of them. For example, moves the planets along their primary paths in right ascension (with 1 degree per year) and projects them on the ecliptic.?

Quite strong words . Now, I don?t known which methor Robert Zoller teaches, neither have I familiarized myself with Lilly?s method, and I don?t know what?s ?right?. But I would like to know the techical difference between Janus and Solar Fire directions.

I haven't read Kolev but it sounds like he understands primary directions. I use Solar Fire and am not familiar with Janus 3. Here is the explanation that Solar Fire gives of its primaries:

"Primary Mundane Directions

Primary directions are created by the diurnal rotation of the earth about its own polar axis. Hence each planet or chart angle is directed along its own diurnal arc, starting from its natal position. Each degree of rotation is deemed to correspond to 1 year in the life of the individual. Aspects are deemed to be formed between directed and natal planets when their relative positions in their diurnal arcs are in angular relationship. (Note that this is quite different from aspects of zodiacal longitude.). For example, if the Sun is natally situated in the 10th house at 90% along its arc from its rise to its culmination, then Saturn will be in natal mundane square to it when it is directed to a position in the 1st house which is at 90% along its arc from its nadir to its rise across the horizon. If this occurs after Saturn has been directed by 24.5 degrees along its diurnal arc, then it is deemed that directed Saturn makes a mundane square to the Sun when the individual is 24 and a half years old.

This method is also known as "Placidian" directions as apparently practiced by Ptolemy, Alcabitius, Montulmo, Lucas Gauricus, Simmonite, Zadkiel, Alan Leo, Pracht, Kloekler and Placidus himself."

These are mundane primary directions and as far as I can tell accord with the method recommended by Ptolemy and used by Placidus. It's the same method used by Ed Falis in his freeware program. I found Alan Leo's book on progressions helpful in understanding this method of primary mundane directing.

Tony

[color=indigo][color=olive]These are mundane primary directions and as far as I can tell accord with the method recommended by Ptolemy and used by Placidus. It's the same method used by Ed Falis in his freeware program.[/color][/color]

Here's the page to obtain Mr. Falis's freeware program.

http://mysite.verizon.net/vze6qirr/myindex.html

greetings, I dont really understand directions (except the kind on a road map) very well, can you give a short summary or point me to a good article?

Granny

I contacted the makers of Janus and asked how they calculate primaries. Here is the response: "Janus calculates primary directions using the Placidus under the pole method. If you wish to trial Janus 3 you can download it from our website. http://www.astrology-house.com/janus/download_trial.cfm"

I think this is the same method used by Solar Fire. There are several rates (keys) in use for timing. Ptolemy used one degree of right ascension on the MC = one year of life. Morin preferred the natal daily solar rate = one year of life. I believe that Naibod and Cardan had their own preferred rates, all in the vicinity of one degree = one year, but over time the forecast can be off by a few years depending on the "key" chosen.

In response to Granny's inquiry about primary directions, the idea is quite simple. All the points and planets in the birth chart are carried along by the rotation of the earth after birth. Each degree of right ascension across the MC = one year of life. It takes about 4 minutes of clock time for one degree to pass the MC. Thus, the first 6 hours of the earth's rotation after birth correspond to roughly 90 years of life.

The "conjunctions" formed by primary direction are quite powerful predictive measures. Ptolemy suggested that when a directed natal planet or point rotated to form the same relation to the horizon and meridian as a natal planet, then the two were conjunct (in mundo rather than on the ecliptic).

Primary mundane directions are a bit difficult to calculate because the planets are rotating in 3-dimensions rather than being projected onto the ecliptic as in the standard horoscope chart.

I hope this makes sense.

Tony

astrojin wrote:

Next, the calculation of oblique ascension, OA

For OA I found the next steps:

1.calculate declination (D)

sin D = sin LONG * sin E

where LONG is ecliptic longitude of the Asc
E obliquity of the ecliptic

2.ascensional difference (AD)

sin AD = tan LAT * tan D

where LAT is latitude of the place

3.oblique ascension of Asc:

a. OA Asc = RA if the Asc is on Equator

b. OA Asc = RA - AD if Asc has north declination

c. OA Asc= RA + AD if Asc has south declination

for RA see astojin previous post