Hester Pulter's poetic manuscript opens with a remarkable metaphysical poem, "The Eclipse," that depicts both a lunar and a solar eclipse. This essay argues that this poem provides the foundation of Pulter's "eclipse poetics," a cosmopoetic discourse focused on time rather than space. The eclipse is an event that encourages reflection on temporal concepts, including duration, repetition, and sequence, because of how it conjoins temporal continuity and discontinuity. An eclipse is simply the result of the alignment of the earth and moon in a particular configuration, but it is experienced as a moment of rare sublimity. Pulter uses this temporal duality to explore tensions between the mundane, the everyday rhythms of life and death, and the sublime, the potential transcendence of temporality itself. The essay explores Pulter's eclipse poetics in "The Eclipse" and other astronomical poems by examining "Black Monday," a predicted total solar eclipse that may have provided a model for Pulter's poem. The final section of the essay proposes that Pulter's eclipse poetics expands the possibilities for thinking about the intersection of science and poetry by providing a model for understanding women's reception of scientific discovery and by expanding what it means to think literature and science together.