The Vedic perspective on astrology is that things are not determined BY what is written in the stars but things as determined are revealed THROUGH what is written in the stars. It is like finding a copy of the entire script of a movie before watching it. We know the plot through reading the script. But it is the one who wrote the script that determines the plot. The author of the script in the stars is the all pervading Cosmic Intelligence aka God.

On the question of 'free will' which is an oxymoron, this quote by Swami Vivekananda is one of the clearest:

"Who is free? The free must certainly be beyond cause and effect. The will is not free - it is a phenomenon bound by cause and effect - but there is something behind the will which is free. Man's will is as rigorously bound by the law of causation as the growth of any little plant or the falling of a stone.

The Soul is free, and it is its freedom that tells you every moment that you are free. But you mistake, and mingle that freedom every moment with intelligence and mind. You try to attribute that freedom to the intelligence, and immediately find that intelligence is not free; you attribute that freedom to the body, and immediately nature tells you that you are again mistaken. That is why there is this mingled sense of freedom and bondage at the same time.

As long as you are in the network of time, space, and causation, to say you are free is nonsense, because in that network all is under rigorous law, sequence, and consequence. Every thought that you think is caused, every feeling has been caused; to say that the will is free is sheer nonsense."