单项选择题
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
A.calculating amplitudes B.calculating great circle sailings by the Agiton method C.entering the Air Navigation Tables (Selected Stars) Pub 249 D.plotting on star finders
A.refraction of light as it enters the Earth's atmosphere B.rotation of the Earth on it's axis C.the body's orbital motion during the time required for its light to reach Earth D.a false horizon