When I heard the learn'd¹ astronomer,
When the proofs, the figures, were ranged in columns before me,
When I was shown the charts, the diagrams, to add, divide, and measure them,
When I sitting heard the astronomer where he lectured with much applause in the lecture room,
How soon unaccountable I became tired and sick,
Till rising and gliding out I wander'd off by myself,
In the mystical moist² night-air, and from time to time,
Look'd³ up in perfect⁴ silence⁵ at the stars.

                                                                                                       Walt Whitman

Analysis

Reading the title of the poem the reader expect the poem will be about someone that is listening to another person. Hear is a verb of perception; this implies that the hearer is passive, so he didn’t decide to listen. Reading the word learned the reader can make some hypothesys: maybe this is an intelligent person. Speaking about the denotative level of the poem, the reader can notice that the poem is in free verse. It generally has no metrical pattern or end rhyme. However, it may contain patterns of another kind, such as repetition. The poem starts with the phrase of the title, in the lines 1-4 there’s a repetition of the expression when I, that reminds an idea of bore and repetitiveness. The proof and figures are word that belongs to a scientific semantic field, and the definite article indicates the perfect remembrance of the things he had seen. The comma creates a pause, a break. In the first part of the poem the protagonist is sitting in a lecture hall and he is listening to an astronomer, that might indicate somebody that uses a scientific method to describe something, or a professor. The “student” is passive, so the author uses a passive form of the verb show to indicate that the protagonist is not involved in the lesson, he is not active. The verbs at the past indicates that the topic is a remembrance, something in the past. The length of the verses increases the boredom of the protagonist. Speaking about the Connotative level, the rhythm is broken in the middle of the poem by the sudden change of He in place of I: this means that the student and the astronomer have two different points of view of the astronomy. In addition, the poet builds a syntactical pattern, parallel structure to indicate two parallels points of view, in the following groups of words:

the proofs, the figures (line 2)
the charts and diagrams (line 3)
add, divide, and measure (line 3)
tired and sick (line 5)
rising and gliding (line 6)

Mystical moist is an alliteration of m to express the idea of the lament,from time to time is an assonance that indicates the idea of the time that passes quietly. The stars indicates the true substance of the astronomy.

In conclusion I think the poet would express this idea: there are many ways to see things, there can be many point of view, but in this poem both the idea of the student and the astronomer can  bring to a big satisfaction.