Perhaps you are not aware that there are two major components in classical Feng Shui studies: astrology and geographical science or better known as Feng Shui. We are already familiar with Flying Star Feng Shui and other Feng Shui schools. Sadly speaking, Feng Shui today is crippled because its twin, astrology part is neglected due to over secrecy of Chinese scholars.
Roughly speaking, classical Chinese astrology comprises of 3 major components:
- Planets, Moon, Sun, Rahu, Ketu etc.
- The 28 houses
- The 12 palaces (Similar but not identical to western zodiac)
Again, there are two charts in applied astrology in Feng Shui: the ground chart (地盘) representing the location and the sky chart (天盘) representing the individual. Both charts must coincide in order to be effective. It is precisely the combined relative locations of all above elements that triggered the earth's power to increase one's luck and wealth. However, it is not so easy to find an optimum solution and a person might need to wait for a long time for the timing. So, now days; many masters just use the position of Sun and the Moon instead as they are more predictable.
Current day Chinese 8 Characters (八字) is derived from classical Chinese astrology that uses actual heavenly bodies. Having said so, predictions using real stars give rise to many problems and the lack of accuracy. Hence ancient scholars used 24 Solar locations ( 节气) and symbolic stars instead for fortune telling and that turned out to be much better than using real stars. This change has not affected the western astrology however.
Likewise, the Purple Star System (紫薇斗数) utilises many symbolic stars to indicate certain events and characters of a person. I would just like to point out that unlike traditional astrology that can be used for predicting almost anything; the 8-Characters and Purple Star systems are only meant for calculating the fate of human and not for any other purposes.
Since classic Chinese astrology is a big topic, I would just stop the discussion here so as not to add more confusions.