Time feels so vast that were it not — Leviathan

Time feels so vast that were it not 1
For an Eternity-
I fear me this Circumference
Engross my Finity-

To His exclusion, who prepare 5
By Processes of Size
For the Stupendous Vision
Of his diameters-
(F.858/J.802)
[1] Time:: multiples of magnifying view in telescope.
[2] Eternity:: stars in the sky.
[3] Circumference:: sphere of a telescope's lens. I:: Earl of Rosse who built the Leviathan telescope.
[4] Engross:: to occupy entirely (OED 5). Finity:: finiteness of one's time and ability.
[5] His exclusion:: Leviathan's exclusion of being limited. Leviathan is the name of the telescope built by William Parsons, Earl of Rosse in 1845.
[6] Size:: the size of lens.
[7] Stupendous:: a hint on leviathan, something huge.
[8] Diameter:: as a unit of linear measurement of the magnifying power of a lens or microscope (OED 2f).

Sir James South thus speaks of the Earl of Rosse's telescope: "The leviathan telescope, on which the Earl of Rosse has been toiling upward of two years, though not absolutely finished, was, on the 5th of March, 1845, directed to the sidereal heavens. ─ Solitude and Society (1846)