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aily motion of the Sun across the sky is familiar to even the m st casual observer. This daily trek is not the Sun
oving as early astronomers thought, but the result of the Earth's rotation. The Earth's rotation also causes the stars to
o the same, scribing out a large circle as the Earth completes one rotation. The size of the circular path a star follows
epends on where it is in the sky. Stars near the celestial equator form the largest circles rising in the east and setting in
polar because they never rise and
ay washes out the starlight.
f the sky can be seen by setting up a camera on a tripod
ilm will reveal semicircles that revolve around the pole.
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the west. Moving toward the north celestial pole, the point around which the stars in the northern hemisphere appear to
rotate, these circles become smaller. Stars in the mid-celestial latitudes rise in the northeast and set in the northwest.
Stars at high celestial latitudes are always above the horizon, and are said to be circum
ever set. You will never see the stars complete one circle because the sunlight during the d
n
However, part of this circular motion of stars in this region o
and opening the shutter for a couple hours. The processed f
(This description of stellar motions also applies to the southern hemisphere except all stars south of the celestial equator
move around the south celestial pole.)
Figure 4-2
All stars appear to rotate around the celestial poles. However, the appearance of this m
varies depending on where you are looking in the sky. Near the north celestial pole the s
otion
tars
also
zon.
stars
scribe out recognizable circles centered on the pole (1). Stars near the celestial equator
follow circular paths around the pole. But, the complete path is interrupted by the hori
These appear to rise in the east and set in the west (2). Looking toward the opposite pole,
curve or arc in the opposite direction scribing a circle around the opposite pole (3).