Here is my 2 cents
The Sun is our AtmA indeed , the Vedic Sun
who rises to bring us from darkness (ignorance) to light (knowledge, enlightenment)
The Moon represents manas, the mind.
When pure its cool, beautiful, pleasant, poetic. The moon.
The AtmA- Sun is ours, Atma chaitanya, inner self, being, is obviously the most intimate. Hence closer than the mAnas-moon which can be "chanchal" and run about helter skelter. Plus , we are not the [material] mind, we are the AtmA.