  Between the mid-eighteenth and mid-nineteenth centuries, long-haul oceanic
voyages of exploration and discovery routinely carried astronomical tent
observatories to support land-based longitude determinations using heavy and
cumbersome astronomical regulators and transit telescopes. Following James
Cook's deployment of a pilot tent observatory on his first voyage to the
Pacific in 1768-1771, the tent design was altered by William Bayly for more
convenient use on Cook's second and third voyages to the Pacific. Bayly's
design became the standard structure of tent observatories assigned to
shipboard astronomers during the Age of Sail. By the middle of the nineteenth
century, a subtle shift in focus had occurred, with tent observatories now
being deployed to observe specific celestial events (such as the 1882 Venus
transit or a variety of eclipses), while longitude determinations increasingly
relied on the novel, compact and improved box chronometers of the day. A
further shift in the application of tent observatories occurred towards the end
of the nineteenth century, when astronomical applications largely gave way to a
renewed focus on meteorological measurements.
