These three grand branches of the esoteric tradition; kabbalah, astrology and alchemy are regarded as the main esoteric sciences.
They complement each other and even if they are interrelated they deal with different realms and answer different questions.

To understand their relation properly we need first to look at the interaction between spirit, soul and body. The spirit is that within you that unites you with the spiritual world, that which is perfect relatively to us. The word inspiration (in-spirit) illustrates what spirit does in the same way as enthusiasm (En theos – with God). Our spirit is the closest we get to God, when we are in touch with our spirit, or the spirit is influencing us we are elevated and illuminated.
Kabbalah has a strong focus on the spiritual world, on the different aspects of God, the celestial hierarchies and the principal archetypical energies behind creation. Central aspects of Kabbalah are related to experiencing or explaining and analyse what streams out from the Godhead through his creative expression. This is called Logos or the Word (See a YouTube video about The Word).
The Word is both creative energy, music of the spheres and the creation of all the principles behind creation; numbers, letters and spiritual beings.
The main aim of the Kabbalist is to connect to this realms, to come towards and closer to the Trone of God and his presence so we can manifest God within. It is to reunite with where we came from, to lift oneself to a higher and bigger level of awareness. In essence we can say Kabbalah is about the world of the spirit, becoming more spiritual, manifesting the spirit in your soul or manifesting heaven on earth if you like.
In the same way Kabbalah is related to spirit, astrology is related to the realm of the soul.
The soul is about your individual identity and how it relates with the individuality of others. It is about your expansion into the social space of family, society and the whole of mankind.
Your star sign with the whole horoscope is the blueprint of your soul. Your horoscope is divided by two lines; creating four quadrants. The line from ascendant to descendant shows the horizon at your time of birth. This signifies which realms are under the horizon of your soul, in the dark or unaware and which realms that have daylight on them. More exactly the ascendant is where the hidden becomes apparent, where the hidden you turns into your appearing personality. The personality is your mask, the word comes from per sonare – to let sound through and refers to the masks used in the theatres in old Greece. The sign of your ascendants colours your mask and gives the qualities of how you come forwards towards others.
The descendant is the opposite of the ascendant, across on the other side of the zodiac. The descendant is where your awareness is brought into the subconscious. This happens in the meeting point with the people close to you. Your family and partners are able to trigger your irrational or unaware aspects more than anybody else. The sign of your descendant colours how you relate to partners in your life. Planets close to ascendant and descendant influences these aspects of your life with their qualities.
The sun shows your identity and the moon shows your emotional qualities. Different planets, sign and houses shows under which influences or colours you are passing through in different times in your life.
In addition the continuous motions of the planets triggers or strikes like a musician strikes a string, the configuration in the birth horoscope differently day by day. Some aspects last for a few days others for months and even years.
This is why astrology answer the question when? In the same way as Kabbalah answers the question who? Since Kabbalah is about the different angelic hierarchies and the different aspects of God. Kabbalah is about all that has a higher awareness than humans. Astrology is about your soul and personality and how it is influenced under different kinds of planetary “weather and colour” throughout life.
Alchemy answer the question what? Alchemy is the art of transforming dull substances into gold or silver and precious stones. In the time of the alchemist any personal growth, psychological process or issues having to do with awareness was the realm of religion and the church. Any vocabulary or speaking of a soul or mind was regarded heretical and could result in a witch hunt. To protect themselves alchemists had to speak about physical substances.

Alchemy could be said to represent how much you have managed to manifest into the body, the daily life or reality. It is what you have materialized in your life.
If you manifest virtues, the gold in your soul has substantiated in your daily life. Your souls gold has turned into physical, stable gold. You have achieved the Philosophers Stone that is able to create gold out of any dull thing.
That is to say that what ever happens to you, regardless of the challenge, you are able to see something good in it and turn it into a situation you can meet with virtue.
Alchemy is the physical world of the four elements. Kabbalah is the spiritual world of the trinity.
When 3 and 4 meet they create either seven or twelve, the world of Astrology standing in the middle in the same way as the soul is between body and spirit.