Stargazing and the Silver Sun
Alteria’s celestial objects such as the stars, the moon and the sun shine on earth and can only be seen if the observer is around high concentration of substance, such as in a fort.
The Alterian sun shines silver, and therefore is named “The Silver Sun”. The rays of that sun hitting earth’s surface keep the gate to Alteria open. Keepers control that by using their forts to prevent some of the rays from hitting the surface.
Alterian stars, much like earth’s stars, shine much weaker than the sun. To see them one must be in an area without any light pollution.
The celestial state affects how easy or hard it is to guard the gate to Alteria from any give location on earth, and informs which fort should be manned. That state is viewed in a process called Alterian stargazing.
The Alterian Trading Company had mapped, over decades, the Alterian celestial state. Stargazing and comparing the current state to the checkpoints on the map allows the watcher, usually a keeper or a fortmaster, to calculate and deduce the effects of the current state.