单项选择题
Sidereal time is NOT used（）.
A.as the basis for star charts B.to enter a star finder C.in sight reduction using Pub 249 D.in sight reductions of planet observations
单项选择题 Right ascension is primarily used by the navigator for（）.
单项选择题 Planetary aberration is due，in part，to（）.
单项选择题 Perihelion is the point where the Sun（）.
