Keats and being Cryptic

Keats’ poems were very difficult. Ode on a Grecian Urn was the easier of the two. Keats’ describes how time is frozen on the urn and how while looking at it, he imagines the scenes with a vividness unique to the imagination. The two sonnets were extremely difficult. I looked up the references. Haydon is a writer. Helicon is a mountain in Greece, and nobody knows what Hesperian shine is. My guess: Keats is playing on the Greeks spirit of belief. He is fascinated with Greek mythology. He is especially fascinated with how it is portrayed in the Elgin Marbles. Keats is lamenting to Haydon, yearning for spirituality. Philosophically, Yeats brings up the gulf between man and the divine.