Meaning of luminous range

lu'minous range'

Pronunciation: [key]
— Navig. Navig.
  1. the distance at which a certain light, as that of a lighthouse, is visible in clear weather, disregarding interference from obstructions and from the curvature of the earth and depending on the power of the light.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.