I can't possibly add anything to the miles already written about this fabulous poem. But I'd capitalize the a in At. Makes the looking more pointed perhaps.
For me the easiest way into this poem over the years has been via the word imagination (and I'll try to cut down on the italics from now on). The sheer opening. Anything a sky can do, that poem can do.
I'll try to convey all that to my writing class this afternoon, before assigning them an essay made from the poem, or not from the poem exactly but the looking at the poem performs. Thirteen ways of looking at a lamp, maybe (the lamp by the window). I'd like to hold my students to 13, too, not just 5 or 6.
I can't spend much more time talking about this poem, except for a word--equipage--and the name of my favourite band--the Bawds of Euphony. And now that I think of it, maybe the upper-case Looking is enough; it's more open.