Brightness contributions on the DS of the Moon and adjacent sky. Vertical dotted line shows the edge of the lunar dark-side (DS) disc. C indicates an atmospheric brightness contribution (airglow and ambient diffuse light) that affects the brightness of the lunar disc as well as the adjacent sky. B is a contribution from background space (such as Zodiacal light, unresolved stars, and scattered starlight) that affects only the sky part of the image. D is a spatially varying halo; it is the scattered light from the bright side of the Moon. A is an incorrect estimate of the earthshine because it is based on the assumption that B is zero.