Where is the center of Heaven? Which part of the Heaven are we measuring, in XuanKong 玄空, QiMen 奇門, DaGua 大卦? Why is locating the central palace, Heavenly Heart 天心 so important? Remember this Poem?
Most of the techniques in Chinese Metaphysics take the reference point of the center of the Heaven as the ultimate datum. Therefore, for the method to works, one has to establish the TaiQi based on the center of the TaiQi - Heavenly Heart 天心. How do you measure Heavenly Heart 天心, that is the undisclosed secret of applications.
More importantly, to locate the Heavenly Heart 天心, one must look upon the sky and determine where is the Heavenly Heart 天心 of the entire Heaven? In modern terminology, where is the Pole Star?
Here is the problem... First, our planet wobble. This is called the axial precession. Wikipedia defines it as, "In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis. In particular, it refers to the gradual shift in the orientation of Earth's axis of rotation, which, similar to a wobbling top, traces out a pair of cones joined at their apices in a cycle of approximately 26,000 years. The term "precession" typically refers only to this largest part of the motion; other changes in the alignment of Earth's axis – nutation and polar motion – are much smaller in magnitude." For that reason alone, through times, we have many pole stars. So where is the Heavenly Heart 天心 of the entire Heaven?
Compared to the birth of the universe, the Chinese Metaphysics are not so "old", fortunately. The earliest method, notably QiMen SanShi 奇門三式 drawn upon the pole star Thuban also known as 右樞 YouShu (Right Pivot) and it is located at ZiWei Right Enclosure 紫微右垣. To be precised it can also be construed as the Celestial Great One 天乙 that sits so close beside it.
First, let's take a detour and see what exactly is TianYi 天乙?
In QiMen DunJia 奇門遁甲, it is also called 值符 ZhiFu or the Lead Deity. It is the highly auspicious and benevolent Deity and with its presence every obstacles will be diminished and even Dreadful Deities will turn benevolent in his presence. With all the stars presence, he is able to even utilize negative stars to its benefit. Here it is technically referred to as TianYi Deity 天乙之神.
In BaZi 八字, it is called 天乙贵人 or TianYi nobleman, in accordance to the following formula, based on the Day Master: -
ShenSha FengShui is a branch of FengShui that utilized BaZi concepts in the application for FengShui. How true is this method is subject for argument but since the idea of TianYi Nobleman is within the concept of BaZi it is also applied here: -
There are 5 formations, but actually 4 if you insist to conform to YangGong 4 structures. All the nobleman direction 貴人方 are incoming water directions from either growth, bath, youth or prosperous. Establishing sitting location of the Stem. Wonder, why the stem only and not the branch also? From here you will notice 2 out of 4 structures are receiving "reversed water" which actually make sense as you receive water you are receiving the nobleman. However, what happened when you face water exit in the Fire and Wood structure? You are actually sitting on Nobleman!
Next, the imperative 12 growth phases. There are 2 different sets of 12 Growth. See HERE for detail. Assuming, Wood structure, if Sitting Gui and Ren are favorable, wouldn't the Ren sitting would be receiving a Mao nobleman in a Death Qi phase based on the Pure Yin Pure Yang principle? Receiving Death means conform with one's life very much live in disgrace and hard work, fortune little and weak, 則生平多困窘勞苦，福淺力薄矣。
TianYi Nobleman Location 天乙貴人方 concealed the secrets to the YinYang 24 mountains if you discern carefully, since it is the Heavenly Heart 天心. Some SanYuan school will used these locations as water locations while I know of one school teaches these as a Sign Board placement techniques to increase customer. For whatever purposes, the one technique that bring results are the best and True technique.
Back to the Heavenly Heart 天心... beside the Celestial Great One 天乙 there is another great star called the Supreme Great One 太乙. TaiYi 太乙 is one of the QiMen SanShi 奇門三式 too complicated to discuss here. Because it is not the pole star, it travels and such occasion brings about great tidings or great calamities befalling a nation.
After 4500 years later, due to the effect of the precession of the earth, the pole star is no longer TianYi 天乙. The current pole star is the Polaris 勾陳一 located at the North Dipper. The LiuRen 奇門六壬 astrolabe or the ShiBoard 式盤 is referring to this pole star as the Heavenly Heart 天心. Could it be correct?
All the classics of XuanKong 玄空 is referring to the Polaris as the Heavenly Heart 天心. When the Dipper moves through its pivot of the Polaris, all the fates of the world has been decided. The secret to change the future lies within the understanding of this Pivot. Here is what XuanKong 玄空 masters of the old is trying to say: -
To conclude, how would you want your Qi to move if you have not established your Heaven Heart 天心? Where is your Heaven Heart 天心?