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30
North South
Zenith
Nadir
Celestial
North Pole
Celestial
South Pole
East
West
Observer’s horizon
Celestial
Equator
star hou
r
ci
rc
le
median of
location
γ
gamma point
δ, declination
α, right
ascension
axis of
rotati
on
hour
circ
le
FIG. D3