The Way Astrology Really Works
The lights in the sky are crystallized Essence configurations - Charms. Every star corresponds to a single Celestial Exalted Charm - the Charms of other beings manifest in different ways. The brightness of the stars is directly related to the proportion of Exalts who know a particular Charm; Finding the Spirit's Shape and World-Shaping Artistic Vision are especially bright. Solar Charm stars are usually quite dim; even before the Usurpation, they were wont to create Charms independently rather than learn from others, and with their return, they are more or less reinventing themselves. Even most stars of the Lunars are not particularly bright; most Lunars of today aren't very well-learned in the traditional arts of their forefathers. The Sidereals are an exception - their knowledge had to be codified and recorded when the Maidens turned their minds to the Games, so the Scriptures were created.
The essential Scriptures, those woven into the Tapestry, are programs written for the pattern spiders; each outlines the procedure for untangling a family of Charms' effects. The spiders with the most expertise in a particular Scripture are known as the College of that Scripture or Constellation. Only Sidereal Charms require Scriptures, since they are also the only Charms that manipulate the Loom directly. The Charms of other Exalts cause snarls and loops, but those of Sidereal making can pull whole portions of the Tapestry out of place. This is the reason Sidereals can't create new Charms: it's because the spiders won't let them create Charm families without Scriptures or the assistance of the Maidens at the Loom, and the knowledge to create Scriptures is long lost. Any Sidereal who breaks this prohibition is summarily executed by the spiders and erased from Heavenly record, and thus the memories of the world. Consequently, the Charms they do have are dramatically better-known than those of the other Celestials, and form the only easily recognizable constellations.
This means that every Celestial Exalt has a constellation formed by the Charms that he knows. For Sidereals, whose Essence-manipulation faculties are severely impaired, these are all more or less the same, and pass universally through the constellation of the Mask, thus creating the Arcane Fate. For Lunars and Solars, finding one's Charms in the sky and mapping out the constellation can tell an Exalt a lot about himself. Unfortunately, the knowledge to do this has been more or less lost, but there is said to be a book, The Thousand Eyes of Enlightenment, which details the occult procedures for this. Its companion, The Riggings of the Soulship, details how another's Charms can be manipulated in order to create certain mystical effects. This book, if it exists, has probably been hidden away by elder Sidereals who fear that using it will anger the pattern spiders. Some suspect that it was methodology from this book that caused the damage to the Mask and the Arcane Fate that Sidereals suffer today.
Terrestrials and spirits have different relationships with worldly Essence patterns, so their Charms manifest in the universe in different ways - there is a species of tree for every Wood Charm (a seed takes root each time a new Exalt learns one of them), a mountain for every Charm of Earth, and so on. Abyssals are linked to the Calendar of Setesh, which is in fact a clockwork monstrosity that is eternally building itself, each gear corresponding to a Charm. Infernals have their Charms represented by the swirling orbs of She Who Lives In Her Name.