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43 42 A little bASic AStrOnOMy the movements of the Sun and Moon The sun rises in the east and sets in the west but this is only strictly true at the equinoxes in March and September. In summer the suns rising and setting positions on the horizon are well to the north of due east and west in winter they are to the south. At the northerly latitude of Callanish, these seasonal swings are more pronounced than in southern England see illustration opposite. The moons rising and setting positions on the horizon undergo a similar variation over each lunar month, but the extent of the swing around the horizon varies over a cycle lasting 18.6 years. The largest swings occur at the major standstills, as in 1987, 2006 and 2025. Midway in the 18.6year cycle the minor standstill, the moons swings are less pronounced than those of the sun. At the northern extreme of major standstill the moon rises and sets further north than the sun ever reaches, setting behind the horizon only briefly the longest arc, opposite. At the southern extreme of major standstill the moon barely rises shortest arc, opposite. At the latitude of Callanish, this event is especially spectacular, with the moon skimming the southern horizon, as seen in the illustration on the next double page. Figures are azimuths degrees clockwise from True North and assume a horizon with zero altitude.
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