> I was trying to figure out how big an area light should be to simulate
> the sun when the light is a lot closer than the sun actually is. Looking
> at a wall about 3m high I noticed the shadow on the ground blurred about
> 3cm. I came to the conclusion that the diameter of my light should be
> about 1% of the distance from the object. To test my theory I looked up
> the diameter of the sun and the distance from the sun to the earth.
> Close enough! The diameter of the sun is 1 391 000 km and the distance
> from the earth to the sun is 149,669,180 km. That's 0.929% :)
>
>

It's interesting to note that the Moon have the same apparant size as 
the sun.
So, you can use the same settings for both the Sun and the Moon, with 
the only difference been the actual brightness.

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