Apostrophe Stars

This poem is really confusing to me. It says he is talking straight to the stars, hence the apostrophe literary term, but is it really stars? If not stars, then what could it be even? Could it be talking about an idea or dream? This is stated when it says: "Yet still steadfast, still unchangeable". Many of our thoughts and feelings don't change in life. Or, it could just be referring to the stars up in the sky that show up during night.