Page:Description and Use of a New Celestial Planisphere.pdf/44

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16th at noon, viz. 5° 4', and the difference is 31'; then ſay, if 24 hours, give this Arc 31', what will 7h 24m give?—Anſwer, 9': which, as her Latitude is increaſing, muſt be added to the Latitude at noon, the 15th, 4° 33', and it makes 4° 42', the true Latitude ſought; then ſeek the Longitude found, 1s 15° 5', in the Ecliptic, in the Planisphere, and point off the Latitude 4° 42', at right Angles thereto Northward, as per Problem 31, for noon, and this point will be the true place of the Moon at the hour and minute required, ſituated in the Heavens, in the Angle between the Whale's Jaw, the Pleiades, and the Ram's North Horn; and you may now take her right Aſcenſion and Declination with the utmoſt eaſe in an inſtant, by Problems 3 and 4; and, if you rectify the Planisphere for the day and hour given, you will find the Moon riſing between those Stars on the East-North-East. The ſame rule muſt be uſed with all the Planets: and note! that when any Planet is direct in motion, or increaſing in Latitude, then ſuch increaſed Arcs, in any number of hours and minutes given, must be added to their place the preceeding noon, and the ſum is the true place at the time required; but if the Planet be retrograde, or decreaſing in Latitude, then ſuch Arcs of motion muſt be ſubtracted from their place the preceeding noon, and the remainder is the true place of the Planet required. Example, in the Planet Mercury, November 2d, 1802, at 6h 30m, P. M. his Longitude at noon, 7s 23° 49', and the third day at noon, 7s 23° 7', which is leſs than the ſecond day, and conſequently he is retrograde, ſubtract, and take the difference, which is 42'; then ſay,