Any system of lights or mirrors which illuminate the living surface of a megascale habitat.
May be powered by fission, fusion, conversion technology or by photovoltaic cells on the outside of the habitat. If the habitat is distant from the star, the p-v arrays can be extended beyond the habitat, or power may be beamed from arrays of collector satellites.
A paper on the illumination of Bishop Rings using luminaires can be found here (pdf file)