The common theory for their power, however, is that the stars are holes in Oblivion to the realm of Aetherius, created by the Magna-Ge when they fled Nirn. Though the Yokudans say the stars were placed there by Ruptga, or Tall Papa, to guide the spirits to the Far Shores. (I do have a theory on how they could be both technically true though.) Whatever the case, their origins give them power, and the ones that make up the constellations are connected in some way that amplifies that. In terms of Tamriel Astrology ...
Thank you Foefaller I have researched a bit using UESP in this search as well but as yet have not come across how the Constellation's came to be other than that they were the remnants of the twelve worlds before the creation of Nirn so was hoping ones here would know more of this.
What I have found so far is that the Nedes were obsessed with the constellations; a book on how the Yokudans chased the stars; and writings of an ancient Yokudan legend of a warrior hero of the Dawn Era who travelled through the zodiac. So it seems somehow that the Yokudans would know more of these Constellations and how they came to be:)
I have also come across ones saying the Constellations are not connected to the Magna-Ge or part of the Magna-Ge so was wondering if you would mind sharing what your theory was.
edit: maybe scrying in Craglorn will reveal more:)