Answer:
When it seemed a truly dark sky at night is one of the most magical experiences one can have.
Explanation:
an opinion is what someone thinks is true but someone else might thing a different way. In this case, the speaker thinks tha a truly dark sky at night is one of the most magical experiances someone can have. someone else might contradict this opinion by saying that its not a magical experiance. The first sentance isn't an opinion because it states that light pollution is an overuse of artificial light and it can cause bad consequences. this is a fact because it's true. The last sentance is a fact because it states something that is happening in the world as well.
I hope this helps you!