Longitude by chronometer highest point, diminish the accuracy of determining longitude by chronometer as a method of celestial navigation. Accuracies of less than error in position are difficult to achieve using the "longitude by chronometer" method. Other celestial navigation methods involving more extensive use of both the Nautical Almanac and sight reduction tables are used by navigators to achieve accuracies of one nautical mile (1.9 km) or less. This only calculates a longitude at the assumed latitude though a position line can be drawn. The observer is somewhere along the position line. Time sight is a general method for determining longitude by celestial
Celestial equator south), the celestial equator tilts towards the opposite horizon. The celestial equator is defined to be infinitely distant (since it is on the celestial sphere); thus, the ends of the semicircle always intersect the horizon due east and due west, regardless of the observer's position on Earth. (At the poles, the celestial equator coincides with the astronomical horizon.) At all latitudes, the celestial equator is a uniform arc or circle because the observer is only finitely far from the plane of the celestial equator, but infinitely far from the celestial equator itself. Astronomical objects near the celestial equator appear above