Where the glow disc's clear centre ends, as a fraction of its outer
radius. The disc is drawn at compressed world radii (scale.ts's log
curve), so the ratio has to be taken between the COMPRESSED radii — the
raw km ratio puts the hole in the wrong place (for the asteroid belt,
0.69 by km against 0.90 as actually drawn).
Where the glow disc's clear centre ends, as a fraction of its outer radius. The disc is drawn at compressed world radii (scale.ts's log curve), so the ratio has to be taken between the COMPRESSED radii — the raw km ratio puts the hole in the wrong place (for the asteroid belt, 0.69 by km against 0.90 as actually drawn).