Astrophel—that's his name. It's an interesting name, no doubt, especially when you find out that "astro" means "star," and "phel" comes from a Greek root meaning "love." So that means… the lover of the star. Okay, that makes sense in a poem with a guy talking to the moon. It also makes sense when you realize that Astrophel's love interest in Astrophel and Stella is… Stella, which is another word for star. Very neat indeed.
Astrophel is totally down on his luck. Just based on his questions in the second half of the poem, it sounds like Stella doesn't love him in return. Astrophel's "constant love" doesn't make her feel all fuzzy and warm inside. No, no, no. She thinks it's just a sign of his lack of wit. Ouch. What's more, Astrophel even implies that she just likes the attention. She "scorns" him, despite his pledges of everlasting love.
Well now, that's enough to make anybody frustrated, sad, angry, and even a little crazy. And Astrophel is all those things in this poem. A guy talking to the moon and making up stories about how sad it is too is not a guy who's having a good day. Like anybody who's down and out, Astrophel is perceiving the world around him through the lens of his sadness. The moon isn't beautiful or serene; it is climbing with sad steps and wearing a "wan" face. As the poem progresses, we feel that Astrophel's tone gets more and more angry. One can imagine him shouting through his tears, "Do they call virtue there ungratefulness?"
There have been lots of sad guys in love who haven't been loved in return. It's bound to happen to everybody at least once. It certainly happened to the poem's author, Sir Philip Sidney, which makes us think this poem is partly a reference to events in his own life. Sure Astrophel is definitely not Sidney, and the two should never be completely identified with one another. But knowing that Sidney was deeply in love with a woman named Penelope Devereux, and that she treated him kind of like Stella treats Astrophel, makes us wonder if the "speaker" of this poem is a ghostly, shadowy, not entirely present, Philip Sidney. Read more about Sidney's frustrated love right here. Just don't go raving to the moon about it.