Where western astrology leans toward the Sun, vedic astrology focuses on the Moon.
It is a matter of Point of View.
Vedic astrology focuses primarily on the sub-lunar world, which is why the Moon takes first position.
But in normal natal chart interpretation, most western astrologers look for one dominant planet in a chart, not necessarily Sun or Moon. There can be several methods, or critieria, for determining the dominant.
One method, which has variants, is to assign point values to each of the planets based on position, motion, aspects etc. The planet accruing most points is almuten figuris, or most powerful planet. The use of astrodynes is such a system, much refined.
The shaping or structure (pattern) of a chart is a convenient way to locate the dominant planet, as for example when we speak of the "handle" planet in a "bucket" pattern. Such a planet is deemed predominant even when it is in a weaker cosmic state. This carries no inherent contradiction, but only says that the planet, whatever its condition, is a predominant force in the life and personality.
Which brings us to weak planets. Simply because a planet is in a weakened cosmic state and does not hold a predominant place in the chart does not deny its potentially significant influence. A pebble lodged in a horse's hoof may incapacitate the beast.
The purpose of locating the predominant planet is to allow us to "type" the personality as Martial, or Jovial or whatever.
In some charts, particularly those in which the planets are rather evenly distributed around the sky, it is difficult to pinpoint a single dominant planet. This is no impediment to interpretation. We know that the person will tend a less-pointed type of personality. We may see first one, then another of the planets assume the dominant position dependent on circumstances. The personality is less well-defined.
We can see that with the wide variety of methods for determining the predominant planet, different astrologers (methods) will produce, at least sometimes, different results. This does not invalidate astrology, nor does it invalidate the different methods. Astrology is, very fundamentally, a system of thought. The horoscope provides us with a hook to hang our hat on. If you closely observe your own work during interpretation you will see that your results depend, to a greater extent than most of us realize, that what we are looking for is what we see. How I look at life, my philosophy and attitudes, affect what it is I pay attention to in a chart and how I view it. The same can be said of engineers or doctors, a good reason to get a second opinion.
