Orson, on this same occasion, wrote of how the inaccuracies of this quadrant affected his measurement, “By a number of observations with the quadrant, I had previously ascertained the latitude and longitude of the Temple at Nauvoo. The latitude being 40°35’48”; the Longitude 91°10’45.” A quadrant, however is a very imperfect instrument for determining the longitude as an error of one minute (1’) in the instrument itself, or in the observation would produce in the calculated longitude an error of (30’) thirty miles. It is a misfortune that we have no sextant in the camp, neither a telescope of sufficient power to observe the immersions and emersions of Jupiter’s satellites.” Sometime in 1846, Brigham Young acquired a sextant and a telescope and gave them to Orson Pratt. These new instruments helped Orson make significantly more accurate observations than he had been making with his outdated quadrant. Orson continued to make observations all along the way with his quadrant, sextant, and artificial horizon on the sun, moon and stars to determine his latitude. He took the latitude of his camp every day that the weather permitted. Orson also recorded eight longitudinal observations at significant points along the way: Loop River, Platte River, Fort Laramie, Fort Bridger, South Pass and Temple Square. In Orson’s field notes, he not only took observations to locate his latitude and longitude, but he also recorded the temperature of each morning, afternoon, and night using his thermometer. He took observations of the altitude of some of his encampments along the way to Utah, using his UCLS Foresights 16
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