The moon is 3.476 megameters in diameter instead of the default 7.697 megameters. It is textured based on the real moon, rather than the vanilla texture.
The sun is 1.391 gigameters in diameter instead of the default 4.488 gigameters.
These changes make the sun and moon visibly much smaller in the sky, approximating what they look like in real life. Consequently, "eclipses", even partial ones, are much, MUCH rarer.
Additionally, the view center for the overworld has been altered, greatly reducing the amount in which objects fade in the sky during the day.
Requires Stellar View to be of any use.