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Appreciating the sun- mutar and appripriate
Bowing to the sun, worshipping the sun, or ascribing independent mystical powers to the sun- assur as avodah zara.
We must be careful to realize that anything in the universe that has any kind of power or force comes from Hashem and Hashem is the one who put that power and force into nature and it is His Will that allows it to continue to exist. If for one nanosecond Hashem stop willing things to exist the world would go back to Tohu Vavohu.