A faint and ashen light on Venus

At http://phys.org/print254991216.html … 'The Mystery of Venus' ashen light' – it seems May is the right time of the year to see the faint glow of ashen light on an unlit portion of Venus during its crescent phase – and nobody knows what causes it. It was first spotted in 1643 by an Italian astronomer, Riccioli, and mentioned subsequently by Herschel, and more recently by Patrick Moore. Others have failed to see it and they went on to assume there has been observer errors, an illusion, or equipment malfunction.