For more than three centuries, visual observers have reported a faint glow emanating from the nightside of Venus. Dubbed the ashen light, the elusive phenomenon is only sporadically visible and usually glimpsed when the planet appears as a slender crescent. In recent years, most authorities have written off the ashen light as an optical illusion. There’s no denying that the human eye–brain combination has an insidious tendency to fill in or complete the figure of a crescent. Most reports of ashen light sightings should be taken with a boulder-size grain of salt.
Venus is invariably a disappointing target for telescopic observers because of an unbroken canopy of clouds and haze
