Philip Sidney created one-way anagram, an advanced form of perfect anagram. His Astrophel and Stella talks about the love of poetry, not Penelope Rich. He set up his own poetry land.
"Astrophel and Stella" is the perfect anagram of "astell a strophe land" or "a strophe land astell."
Strophe has the definition of "a series of lines forming a system, the metrical structure of which is repeated in a following system called the antistrophe. Also, in wider sense, one of two or more metrically corresponding series of lines forming divisions of a lyric poem (OED)."
Astell has the definition of "to set up, set on foot, establish (OED)."
This means the original spelling of Astrophel is correct. Those who tried to amend it to Astrophil didn't know Sidney's wordplay.