What is the context of the poem "When I Heard the Learn'd Astronomer"?

The context of Walt Whitman's "When I Heard the Learn'd Astronomer" can be gathered from a close look at the descriptions that Whitman provides throughout the poem. Whitman's narrator describes not only listening to an astronomer, but also seeing "the proofs, the figures . . . ranged in columns" in front of them, along with "charts and diagrams." At first, this might sound like a traditional classroom setting. However, this astronomer isn't a teacher.
Whitman's next descriptions clarify that this is a public event. The narrator says they are "sitting" while the astronomer "lectured with much applause in the/lecture room." This reveals that Whitman's narrator is attending some sort of public lecture regarding space. In Whitman's time, these sorts of public forums would be the way in which many people would get their information regarding new findings and current research.
Whitman's narrator is there for that very reason, but unlike the other people attending, the narrator is not happy with the lecture. Upon seeing all the figures, the narrator begins to feel sick because the findings are taking the wonder out of the night sky, and so the narrator leaves, content to wander off "[i]n the mystical moist night-air" and look up "in perfect silence at the stars."