Basically, "Dangerous Astronomy" opens in the son's dark bedroom and remains there until the final stanza when the speaker "walked outside and praised the stars." However, throughout the poem, a tension between the dark bedroom and the "farthest star" is maintained through repetition and contrasting imagery.
So, figuratively, the poem is taking place in that constant motion between the sky and the earth, as if the speaker is looking up and down, inside and outside, trying to figure out where he belongs in the shifting dynamic of family roles.
On the other hand, we're inside a home and despite the father's flailing emotional status, things seem pretty good. The speaker is well-intentioned, the wife comes to the rescue to the feed the son, and the baby is just doing what babies do.
What's fascinating about the setting is that beneath the surface, Alexie uses the crying baby, the darkness of the bedroom, and the close proximity of the whole family together in one room, to show us a more complex emotional world at play within the speaker.