User blog comment:Supahbadmarine/Navigation without the Astronomicon/@comment-8464494-20150828022821

I think its more that the Emperor's spirit itself is the light, not so much the magnitiude of his presense though thats a factor. I'd imagine looking from the Warp that the Eye is basically alot like all the other swirling gibbering evilness. Note however that CSM get around the galaxy just fine without the Navigators, plying the will of the Gods or using their own Sorcerers. Plenty canon races make use of other means as well, though most are just unknown alien bullshit tech.