The earth has a north pole and a south pole, which is 30 degrees, and then find out the time of the branch on the moon at 65438+ 15 in early October, 2. . . Determine the deviation between day and night to calculate the time after dusk. Because the earth is autobiographical, the time difference divided by latitude 30 degrees is how long it is at a time, and then drawn as 12 parabola is the time, and then the moon period is set to 30 days, which is based on the lunar calendar, and the date is calculated as 15 of each month. . . Then the first question came out, and the second question was to find out the longitude. One longitude is 4 minutes, and then the latitudes and longitudes of those seven places are all known, and they all come out.