Actually the opposite is true. Shooting the bright moon is just like shoioting a bright daylight subject. It is reflecting the light from the son and you should be able to capture it using the sunny 16 rule. That is the reciprocal of the ISO at f/16. But something else came into play here. I had a heavy lens mounted on a cheap and somewhat flimsy tripod, so to try to eliminate shake, I shot this at shutter priority at 1/640 sec and f/6 set at 200 ISO.