Many astrologers think they create a complete progressed horoscope by calculating the secondary positions of the sun, the moon, the planets and maybe the lunar node and adding to these positions something they call ‘the progressed cusps’: first calculate the progressed MC by one way or another, then calculate the corresponding ascendant and intermediate cusps for the local latitude of birth et voilà.

Although this is handy in daily practice (one has to have a complete set of progressed points) and one can get definitely consistent and positive results, one should realize that it is not the complete truth for you without the complete set of primary planets that are also active at the time. It is possible to calculate the primary positions of sun, moon, node and planets too and together with the progressed (actually primary) cusps, that almost any astrologer uses, this gives a real complete primarily progressed horoscope. Personally, outside of the radix-circle, I make one progressed chart with all the primary cusps and planets plus, in a third circle, the secondary Sun, Moon and planets.

At this point it is important to realize that when we calculate progressed cusps we calculate in fact primary cusps. There is no such thing as secondary cusps that move forward by about one degree a year, for secondary directions are based on the assumption that 1 day equals one year and in one day the cusps undeniably move forward by 361 degrees, not by just one single degree. This means that if one uses progressed cusps one is not using secondary cusps but primary ones.

Primary Directions are far older than secondary ones. Secondaries were more or less invented by Placidus. Primaries are already described by Ptolemy (A.D. 150) in his Tetrabiblos, Loeb Edition, Robins’ translation, p. 293-307, Ashmand Edition p. 95-100. This text however is so obscure (as you will see when you try to read it) that through the ages heavy discussions have been held on its interpretation. Many astrologers (Cardanus, Morin, Placidus, Kühr to name a few) had their own variant of p.d.’s. Primary Directions, in spite of their fame, this technique did not become a standard tool for astrologers to use.

At the beginning of the seventies, the arrival of calculators with trigonometric functions helped calculate p.d’s which are invariably difficult to calculate by hand. It was only with the aid of calculators with trigfunctions, that conducting real research became possible.

1. DAY-ARCS DEFINED

The day-arc of a celestial point is the time it takes for this point to traverse its path from the eastern to the western horizon, not the actual arc it traverses on the sky in that same time. Thus it is possible to define a planet’s position at the sky not only in terms of celestial coordinates, as is usually done, but also in terms of the time that has passed since it rose or even in the fraction, the percentage, of the time that has passed in relation to the total time of its day-arc. Paradoxically enough this time-arc usually is expressed not in hours and minutes but in the number of degrees of the celestial equator that passes over the local meridian during that time (a very constant measure), so day-arcs, although being time-arcs, most confusingly are calculated by trigonometric formulae.

The day-arc of a point is dependent on the combination of its declination and the local latitude and may vary greatly. Their mean value is exactly 180 degrees.

In practice, for technical reasons we mostly use half day-arcs, the so called semi-arcs, the time it takes for a point to rise from the eastern horizon to the MC, or to set from the MC to the western horizon, which takes as much time.

Night-arcs are defined from the western to the eastern horizon and under the horizon through the IC.A short day-arc for a certain point is always compensated by a long night-arc and v.v. Together they are always 24 hours equals 360 degrees.Circumpolar points (points that for a given latitude do not rise or set but constantly describe circles above or under the horizon) have no day- or night arcs; one might also say they have a day- or night arc of 24 hours or 360 degrees.

2. PLACIDUS HOUSE SYSTEM

Let us start with true Placidian housecusps. We should understand that they were originally invented by Magini (later latinized to Maginus), who was the first to define them in the pure way.

Ascendant: The ascendant is that point of the ecliptic that is exactly to begin traversing its own day-arc and has actually traversed nothing of this path.
Cusps:
~ The cusp of the twelfth house is that point of the ecliptic that has traversed 1/6 of its own day-arc.
~ The eleventh house 2/6 of its own day-arc
~ The MC 3/6 equals 0.5
~ The cusp of nine 4/6 equals 2/3
~ The cusp of eight 5/6
~ The descendant is the point that has traversed 6/6, equals 1, equals its entire own day-arc.

• Important: the ecliptical point at the MC is always exactly halfway its day-arc. The same for the house-cusps under the horizon.

Note that the ascendant, descendant and the MC/IC are usually defined in purely trigonometric terms. For example, ‘the point of the ecliptic that crosses the horizon’ or ‘the point of the ecliptic that crosses the local meridian’ but in this context this would be misleading. If you define these points in this way, you see them as parts of a purely geometric house-system as Regiomontanus. Of course the net result is the same but nevertheless it is important to realise that within a housing system based on time-arcs, this is not the right definition. Indeed the trigonometric view is the easiest way to calculate the ascendant but this is no more than a lucky coincidence so to say.

One could say there are two ways of calculating cusps generally, the one based on trigonometry, f.e. Regiomontanus, the other one on day/night arcs, f.e. Magini/Placidus. Both of them are respectable, we only have to decide which one gives the best results. As a convinced Placidianist, I think it is nice and beautiful that we use a trigonometric definition for positions in the celestial ecliptic (in zodiaco) and time-arcs for positions in the earthly houses (in mundo), a kind of symmetry made in heaven.

The only problem is that the intermediate cusps by Magini are difficult to calculate: there is no direct way, no direct formula, to determine their exact position in the zodiac. The only way to get them almost exactly is to make an educated guess and then by repetitive approach (‘successive substitution’ as it is officially called) getting closer to the desired value until the deviation (that will always be there, no matter how small) has become so little that it is neglectable as one tenth of a second of arc. Now we see why it is easier to calculate the ascendant and the MC trigonometrically since for these cusps at least we do not have to use successive substitution.

Nowadays, even the slowest computer calculates Placidian cusps in a split-second but for centuries this was quite a stumbling block for astrologers. Therefore, Placidus invented a system to calculate these intermediate cusps directly, with some deviations. He therefore used the concept of Polar Height, which is in fact alien to the realm of day- and night arcs. This was extremely useful however since for regular local latitudes up to say 60 degrees north or south the deviation is acceptable. A Magini-cusp is better, even if it deviates by half a degree, than one of Regiomontanus which has been calculated exactly but that is useless for astrological purposes in our Placidian eyes.

Placidus’ simplification enabled astrologers to calculate intermediate Magini-cusps as fast as Regiomontanus’. Placidus’ system became popular amongst them and was called “Placidus”. One might say nowadays, with our PC’s, we have returned from approximate Placidian cusps to real Magini ones although we still call them Placidian.

3. PRIMARY DIRECTIONS. After the above elaboration, we may now discuss p.d.’s, since they are one family house systems.

What are primary directions anyway?

Primary directions are systems where the planets, independent of their own speed in the ecliptic, are kept in the same position relative to their day/night arc as they were at birth while the MC is progressed. This means that they will always maintain the same position in the progressed houses as in the radix if they are Placidian. It is also possible to calculate primary directions based on the planets’ positions in Regiomontanus-houses but that will be another article to write.

• If you are afraid of technicalities, it may be sufficient for you to know that, in p.d.’s all planets and cusps progress through the horoscope, each with a speed that varies from about a half two and a half degrees a year, and skip to catch 6.

In the case of Placidian cusps, a planet that is radically ‘halfway’ the tenth house will have traversed the mean between 2/6 (cusp eleven) and 3/6 (M.C.) of its own day-arc, equals 5/12th of its own day/arc equals 0.416666… This is the proportional factor for this planet and it should be calculated for each point (sun, moon, planets, node) in the radix except for the cusps for we know on beforehand that their proportional factors will be 0, 0.1666... , 0.333… etc. by definition.

If we calculate the progressed M.C. for any time in life, we calculate the corresponding ascendant for the latitude of the place of birth; the intermediate cusps may be calculated in the usual way by using the proportional factors 0.16666… , 0.3333… etc. We may also calculate each progressed (primary) planet using the same formulae as for the cusps, only with the planets’ proportional factors we calculated earlier for the radix.

If we were to draw the progressed chart as if it is a radix, we would get a surprise: the figure would look much like the radix, (f.e. planets radically on a cusp would still be on the same primary cusp). All cusps and planets progressed by a different number of degrees and not by the same number of degrees for all planets. It is the same way as the ascendant progresses with a speed different from the M.C., dependent on the local latitude. Each point is primarily progressed with its own individual speed, dependent on its radical position in the houses and on the local latitude. Progressed (= primary) ascendant’s speed varies by the years, so the primary points’ individual speeds are not constant. They can however be calculated for any date with amazing precision.

The main speed for p.d.’s is about the same as the solar arcs. It varies from less than half a degree to more than two degrees and as said above, it is different for each point in the horoscope. However, just like Placidus and most other housing systems, it shows a tendency to produce equal houses as one gets closer to the equator. Therefore, primaries tend to coincide with solar arc directions in tropical areas. For European and North American latitudes however, differences can be considerable as we will see. The results will differ depending on the house system used. The first problem we have to solve is, determine the house system we should use as the foundation to caluclate p.d.’s. Will you use Placidus or Regiomontanus house system? (Other house systems are seldom proposed for this purpose). In this article we will use Placidus to get the best result.

You may have another questions to resolve before you continue with your p.d calculation: Should you use the Pars? Should you progress primarily the Pars itself or should you calculate primary sun, moon and ascendant first and then from these calculate the Pars as usual by adding and subtracting?My answer is, I really don’t know. I dropped the Pars many years ago and lived happily ever after.

4. PROGRESSING THE M.C.

The first step in calculating p.d.’s for any desired date is calculating the primary M.C. And here we come to the second problem concerning primary directions: What is the right speed of progressing the primary MC?Ptolemy suggested one degree a year in Right Ascension on the meridian for each year of life.

Later authors corrected this to 360 / 365.24 degrees a year, the so called mean or Naibod-measure of 0.58’18” a year.
Tycho Brahe had the idea of using the progression of the sun in right ascension on the day of birth as a constant measure for each year in life.

The most used measurement of time for progressing the M.C. is progressing it in longitude at the same speed as the secondary sun. See for a survey of this history the Astrologia Gallica Book 22, p. 77 and further.

5. ON PLANETARY LATITUDE: A NON-PROBLEM

Through the ages it has been a point of discussion whether the latitude of the moon and the planets should be reckoned with or not. The sun and the lunar node have no latitude by definition.

I do not see how this can be a problem. If we are to reckon without planetary latitude in the radix (as we all do), and we do reckon with it in p.d.’s, we get a paradox. For example, if Pluto has a latitude of 10 degrees, then 1 second of time after birth its primary position will be many degrees from its radical position while of course one would expect it to be virtually identical to the radical one.

One dutch school of astrology solved the above problem in a radical way: First, calculate a planet’s proportional factor in the radix reckoning with its latitude. Then, calculate what ecliptical point has the same p.f. and that’s the radical position of this planet. Unfortunately some decades after they developed this idea, Pluto reached its maximum latitude, which meant that in the course of each day for the latitude of Europe, this slowest planet rushed through the zodiac ten degrees forward and then ten degrees backward which is most incredible. The only logical solution (which in practice gives by far the best results too) is to neglect planetary latitude.

Wim van Dam’s system of Primary Directions: Use time-arcs, neglect latitude and use the progression of the secondary sun in longitude as the key for the measurement of time.

Although the system is simple and logical (once you’ve found it, that is) and I had thought out all of this theoretically around 1974, without the arrival of calculators with trig-functions about 1974/1975 I could never have checked it all. Remember it is the inevitable repeated calculation that makes calculation of each point of the primary horoscope a cumbersome operation. And now with a computer at every astrologer’s desk the system is available for every astrologer.

6. HOW TO USE THESE P.D.'S?

Primary directions are a part of the classical heritage of astrology and should be treated as such. Do not use them in combination with midpoints, fictitious planets, etc. for you will not have any profit of them. Of course, you can use them with the node and even the newer planets Chiron, Uranus, Neptune and Pluto but all in the same classical way.

In order to have full profit from them, you should use such old-fashioned ideas like houses, rulerships, and, a surprise for most astrologers today, degrees of exaltation. Whenever you find an aspect or an antiscion between a primary planet and a radical one, you should check what houses these two planets are the ruler of. To make things seemingly worse, for Jupiter you should check both the house with Sagittarius on its cusp and the house with Pisces on its cusp (for Neptune only the house with Pisces, etc. and a house with a planet’s degree of exaltation on its cusp is (also, mainly) ruled by this planet! These houses are the most probable to play a role in the event indicated by this progression, followed by the houses where they are placed in the radix and the natural houses of the planets (the moon for the fourth house etcetera). In practice you will see that some houses are stressed more than other ones and these houses are the most likely ones to play a role.

Also important is the choice of the aspects used. As always I use the following set of aspects:

The inclusion of the tredecile (108 degrees) will be astonishing for most American astrologers but it is the supplement of the quintile (72 degrees) and I have found them both as effective (and benevolent) as the sextile, using a smaller orb, about 2.30 degrees in the radix.

No more aspects (except of course the antiscion) are needed and certainly not the inconjunct (150 degrees) that I think one of the great errors of modern astrology. Maybe it has some value in ‘psychological’ or ‘Jungian’ astrology but I don’t take these branches seriously. In fact, for the critical astrologer who does not take for granted anything just because it is written in a textbook, using primary directions is a very good way to learn which aspects are more significant and less significant.

Also I have noticed that the mean node, when it differs from the ‘true’ one, gives far better results, i.e. the time is closer to the real date of event. The node in my chart is a good example: the ‘true’ node is at 0.03 Aries and the mean one at 1.10. As we will see, the discussion on which one is the right one can be decided by p.d.’s and in fact it has been decided.

Important Note: Although it is not possible to attach fixed concrete significances to each combination of two planets, it might be possible to attach color, an abstract keyword to each combination that blends the actual event. Thus a bad aspect between Mars and Saturn will always have something violent and a bad aspect between Mars and Uranus the same plus something sudden. The combination of Venus and Jupiter will mostly form a pleasant influence resulting into a feeling of happiness and well-being. However, on what specific area of life the event will be produced, that is indicated by the houses involved and should not be part of these recipes.

Aspects between a cusp and a planet (be it a primary cusp to a radical planet or v.v.) are mostly more easy to interpret. The own significance of the cusp in combination with the nature and/or the rulership of the planet will mostly give a clear indication of what is to be expected. Note that an aspect from or to a cusp will automatically mean an aspect to the opposite cusp too. Always look which cusp is the most probable to be related to the event in combination with the nature of the planet involved and the house(s) it rules.

Aspects to and from intermediate house cusps are most informative too. Beginners however, will do well to use only aspects between a house cusp and its actual or natural ruler. For example, if you have Leo at your 9th cusp, pay attention to the aspects of this cusp to and from Jupiter and the Sun, etc.

Very important in the interpretation also are possible relationships in the radix: the points involved may be in aspect in the radix, or the one may be the ruler of the