航海英语天文航海章节练习(2018.02.14)

单项选择题
In working out a local apparent noon sight for your latitude，you subtract the Ho from 90°. The 90°represents the angular distance from（）.
A.the equator to the elevated pole
B.your horizon to your zenith
C.your zenith to the elevated pole
D.the geographical position of the Sun to the elevated pole
单项选择题
A marine sextant has the index arm set at zero and the reflected image of the horizon forms a continuous line with the actual image. When the sextant is rotated about the line of sight the images separate. The sextant has（）.
A.error of perpendicularity
B.side error
C.prismatic error
D.centering error
单项选择题
Right ascension is primarily used by the navigator for（）.
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
单项选择题
Diurnal aberration is due to（）.
A.motion of the Earth in its orbit
B.rotation of the Earth on its axis
C.the body's orbital motion during the time required for its light to reach the Earth
D.a false horizon
单项选择题
Capella is found in what constellation? （）
A.Gemini
B.Auriga
C.Libra
D.Crab
单项选择题
In the horizon system of coordinates what is equivalent to latitude on the Earth?（）.
A.Altitude
B.Zenith
C.Declination
D.Zenith distance
单项选择题
A sidereal day is approximately how much shorter than a solar day?（）
A.4 minutes
B.8 minutes
C.12 minutes
D.16 minutes
单项选择题
Sidereal time is used by navigators when（）.
A.used with the equation of time
B.used in the form of LHA Aries
C.calculating the time of moonrise
D.determining local apparent time
单项选择题
Apparent altitude is sextant altitude corrected for（）.
A.parallax and personal error
B.inaccuracies in the reading and reference level
C.visibility and magnitude
D.All of the above are correct
单项选择题
A first magnitude star is（）.
A.2.5 times as bright as a second magnitude star
B.3 times as bright as a second magnitude star
C.5 times as bright as a second magnitude star
D.10 times as bright as a second magnitude star