What association do the Moon and Venus have in common in astronomy?

A long-standing mystery of Venus observations is the so-called 'ashen light', an apparent weak illumination of the dark side of the planet, seen when the planet is in the crescent phase. The first claimed observation of ashen light was made as long ago as 1643, but the existence of the illumination has never been reliably confirmed. Observers have speculated that it may result from electrical activity in the Venusian atmosphere, but it may be illusory, resulting from the physiological effect of observing a very bright crescent-shaped object." In astronomy, Venus has been called the twin sister of Earth. Both planets are about the same size. If another planet could support life, it was once thought to be Venus (of course, now it's realized that the heat and sulfur make that impossible). What association do the Moon and Venus have in common in astronomy?