What does Lux mean by constellation in "The Voice You Hear When You Read Silently"?

When the poet
uses the word "constellation" he is using it to mean a whole array of things -- not
just one.  He is saying that when you read silently to yourself, you are exposed to a variety of
different sensations (because he says that it is a "sensory constellation) not just one
sensation.

When you read to yourself, you experience many things.  You
"see" things, of course, but you also engage your other senses, he says.  Lux says
that you can feel things and smell things.  You can hear the oats as they pour into the feed
troughs.  You can see how dirty the cow's haunches are, and you can probably smell it as
well.

The whole point of saying that there is a "sensory
constellation" is to tell you that reading can be a very vivid experience that impacts all
of your senses (at least in your mind).