单项选择题
In the horizon system of coordinates what is equivalent to the equator on the Earth?（）.
A.Prime vertical circle
B.Principal vertical circle
C.Parallels of altitude
D.Horizon
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相关考题
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单项选择题
In order for a star to be used for a sight at lower transit，the star must（）.
A.be circumpolar
B.have a declination equal to or greater than your latitude
C.have a GHA of 180°
D.have the SHA equal to or less than the LHA -
单项选择题
In low latitudes，a first quarter Moon will always rise at about（）.
A.sunrise
B.1200 LMT
C.sunset
D.2400 LMT -
单项选择题
In general，the most effective period for observing stars and planets occurs during the darker limit of（）.
A.sunset
B.civil twilight
C.nautical twilight
D.astronomical twilight
