One of the most simplistic explanation of Astrology can be provided as follows:
It is based on the premise that there is a co-relation between microcosm(small things in life) and macrocosm(the big picture) and that every worldly activity is related to others and hence every effect has a cause and every cause has an effect. The other premise is that psychology and physical activities and events can be co-related to numerical logic and vice-versa(implying that nothing in this world is without reason and explanation, whether we know or understand it or not).
Thus, some astronomical representations are analysed and used to interpret and explain events in the physiological world of time and space. These are done by various techniques or methods which vary across the world. Some people claim these techniques to be logical and scientific while on the other extreme some people find no science or rationality in it.
The traditionally popular stream of astrology in India has been what is called Vedic Astrology. It entails drawing up of charts depicting the universe consisting of planets, nakshatras, rashis and bhavas in various positions under different conditions, much like drawing world maps of weather, politics and geography and then super imposing these maps to understand how the world looks at different times and places. Much of these details can now be generated using various software and are also available freely on the net. These along with other data is called horoscope or simply charts. Usually date, time and place of birth are the input parameters required to generate the horoscope.
There should not be any dispute as to the generation of these details and the on-going time charts or a kind of calender(called “panchang”) are also used to make calculations about festivals and events like marriage, etc. and also have variations based on various places and systems adopted for calculation. Most of this data is now easily available through astronomy, relates well with actual astronomical events and hence easily verifiable for its correctness.
So that much is fine. The debate starts when all this data is analysed and further used to make interpretations and draw conclusions for certain purpose. Is the interpretation universal or is it different for each person? What is the basis of interpretation? Is that basis or its assumptions correct? Is the interpretation reasonable and scientific? Is the person making interpretation objective and qualified to be able to do the same? These are some questions which should be considered before blindly believing any predictions of future and assurances of magical remedies.
One should remember, as long as anything is reasonable and scientific, it does not require blind faith or magic. Science is boring and parts of astrology are also a bit boring, just like study of medicine or chemistry. And just like a person with some understanding of chemistry is not necessarily qualified to prescribe medicines, similarly, a student of astrology does not have any magical powers to change someone’s future. There is a fine line between wisdom and foolishness, and that line is of knowledge. Thus, knowledge of astrology can be useful and positive in one’s life as it helps one become aware and prepared. On the other hand, ignorance, blind faith and mis-interpretation can lead to hardships.
For example, if sun is positioned in fifth house in leo in pusya nakshatra in the chart based on inputs given, then that is so. Whatever effect that position makes will be there. Now suppose it can mean that the person will have a public life. Is that good or bad? Depends, as a family oriented person may think it is disturbing while a social person may think it is good. Similarly, Astrology cannot be a recluse to karma. In Bhagwad Geeta, it is clearly explained that Karm Yog is the best and that such Karm be performed without any desire. That would make astrology useless for many people who consider it a means for future-telling.
Astrology is a subject, it is not a technique or technology. Only when a subject has been mastered so much by its practitioners that it has been evolved to apply techniques for easier or advanced processing then we can consider its maturity, like Physics leads to Electronics Engineering and that leads to Mobile Technology. Simply studying Physics does not necessarily means one can repair mobiles.
So here in the end comes the most important premise of astrology, which is to first have faith in self and in God that your life is for serving its best purpose whether through gain or pain and one should relish all the experiences of this difficult but beautiful life given to us.