The following link beautifully explains how astrology 'works' by means of using various inter-connected components of the Universe.
On the basis of such inter-connection, the writer Mr Vamsee A R K has explained how convincing answers can be found to many a question on astrology, besides establishing its dependability.
The only place I wish to note here is why we don't use outer planets such as Uranus, Neptune etc in Vedic astrology. The reason is that we can not see them as we dont see their light. Sage Parashara has explained this issue saying that we can not consider those entities whose light do not reach us. Jyothisha, by its very name is about knowledge of Light. Those entities whose light do not reach the earth are not part of the inter-connecting mechanism with life on earth.
Mr Vamsee has explained this in different trerms such as this:-
"One question that people generally ask is that why does not vedic astrology use planets like pluto, uranus etc? Is it because they were not discovered during vedic times? Can we do any better if we use them? The answer is too obvious once we understand the basic theory of astrology. The answer is that they are not needed. To say this mathematically, if it is sufficient to use variables x1 to xn to describe a system completely why should one use more variables? They are just redundant i.e they do not give any extra information. Even if one tries to use lets say pluto's longitude (call it 'u') we will end up getting a relation like z = 2cos(x)+3sin(y)-0tan(u). As the coefficient is zero, one does not need 'u' to find the value of 'z'!"
The complete article can be read at
http://arkvamsee.blogspot.com/2008/07/astrology-and-advaita-divine-connection.html
Some excerpts:-
"When a stone is thrown into a lake, ripples get created in the lake. The stone is the cause and the ripples are the effect. When an intelligent person standing at the shore of the lake sees ripples coming, he can safely infer that a disturbance was caused ( a stone thrown etc.) to the lake. Similarly, to understand the state of an element in a completely interconnected system, it is sufficient if one has enough information about few other components of the system. The amount of information needed about other components is dependent on 1) what information we seek from the component under analysis and 2) the nature of interconnections between the various components of the system. For a system like this universe ( which is completely connected through consciousness), it is sufficient if we have enough information about few components to understand any other component. This is applicable to all the elements of this universe. And this is the very basis of spiritual powers, which are exhibited by great siddhas and others. So what has this got to do with astrology?
What does one need to predict a person's future? The sum total of all the past impressions on his/her soul. If these impressions can be found somehow, then any one can predict the future of a person based on these. But getting the spectrum of impressions is beyond a normal human being's mental powers! But the theory about an interconnected system mentioned in the previous paragraph comes to our rescue. One can get the spectrum of impressions of a new born, by taking enough information from some of the other components of this system, the universe. Astrology is based on getting this spectrum by observing the planetary positions at a person's birth ( please note that planets are just another component of this interconnected system). The tough problem of getting impressions of a person is solved now. Now the next step is to use the planetary positions as a proxy for the impression spectrum and just decipher this based on the nature of the interconnection between these two components of the system (planetary positions and impression spectrum). An example for this is like if z=2cos(x)+3sin(y), where x, y and z are longitude of Sun, longitude of Moon and sum total of impressions, one can easily find out z if x and y are known. But knowing this relation is dependent on the nature of interconnections between various components of the system. Thanks to the ancient rishis, who understood the nature of interconnections and formulated the rules of astrology. Thus a combination of advaita, karma theory and theory of interconnected systems resulted in the discovery of a divine science "Astrology". Understanding this basis of astrology, solves many questions that are posed by researchers about Vedic astrology. "
