Why does it need moon light?
Here’s a real crystal ball used every day by a professional psychic, (me) now filmed for your focus and attention. http://www.psychic-junkie.com/ask-the-crystal-ball.html
a crystal ball, a crystal of any type, needs a period of sunlight to energize it. it is not to be used during this period. it is said that anything not of positive force would be drawn to and burned in the heat of the sun, probably because it is the hottest heat source known to man.
All crystals require being charged by the full moon. I would not look into the crystal in the sun, as you will damage your eyes. Other than that, the sun will not harm the crystal’s energies.
gazing in the ball you are searching for shadows of the past or reflections of what may be. Sunlight banishes shadows and causes too many reflections. On a more practical level reflection of sunlight just like gazing directly at the sun is very bad for the eyesight. If you want to scry in broad daylight a nice wooden bowl of spring water is a good alternate to using crystal.
Sun purifys and cleanses. In the case of a crystal ball, it would neutralize important energy.
So always, in a very reverant way, cover it with a black or dark cloth, and put it away till you use it for scrying.
because it’ll stop the black magic!
Actually it depends on the material that the ball is made of. Some crystal balls respond better to moon light than sun light. Also there is the whole light reflecting thing, you could burn out a rod in your eye from the reflected sun light
obviosly the sun would be blinding and the moonlight more romantic.