re: well
Venus passes very regularly behind the sun! Every time it orbits the sun, it passes at some time behind the sun.
However, it can pass behind the sun and be completely physically hidden by it and then, of course, it's invisible to us.
Or it passes behind but just above or just below the sun.
Then, the glare and the radiations ftom the sun are such that it can't be observed either, except by Soho's Coronograph.
Raoul