Considering fluff area look a little starved, i'm going to state my crack pot theory on how the golden throne and the Astronomicon work in the warp. I believe the throne is the light house keeper, who run and maintain the light of the astronomicon, the Emperor keeps the light in a steady obedient form spaning 50,000 light years across, the galaxy. Its fuel by a mere 1k pyskers a day, and not just any pysker i believe most of these are beta plus verging on alpha. Only the strongest and best and talented or should i say those who qualifies can fuel the astronomicon. Like burning dried brown wood, and not burning wet or green wood. (not sure why burning green wood is bad, but i was always told not to burn green wood). As their energy which is warp energy pours into the Emperor guiding hands, he turns their warp energy it what i will call Salt warp energy. I call it salt warp Energy, because it hurts deamons and deter them from going into the light and traveling down the tube in attempt to tap on the door a little. It could also possibly destroy them on contact.
Now this light span out into the warp, like a light house spears it light offshore so ship can see it and not hit the rocks, the astronomicon do the same thing. It pushes up and out 50,000 light years and guide ships around the warp, and no, people on the ship don't look out the window and say there's the light there so we go that way. Only navigators can see this light, i'm going to suspect see it very clearly to navigate open through the waves of the warp. Now i believe, that the light does a secondary thing, which is hold back demonic chaos accursion on all planets with in the 50k light span, or should i say well with in. Its the only way i can explain why most of the Imperium isn't being attack by deamons due to people with latent pysker powers running around unchecked, which could be alot on almost every planet. I say the light is almost a blinding screen and nto a real sheild , and it simply reduces the amount of chaos presence well within the influence area, which also could explain why in dow chaos wanted a main way through to terra. Which leads me to think it reduces the warp storms in the area of influence to or prevent them from occur freely so requiring possibly cults and a lot of pyskers to break through the screen and signal chaos.
So thats a part of my crazy crack pot theory there, anyone else got something to add feel free.