单项选择题
A.4 minutes B.8 minutes C.12 minutes D.16 minutes
A sextant having an index error that is off the arc has...
单项选择题A sextant having an index error that is off the arc has a（）.
A.positive correction B.dip error C.negative correction D.semidiameter error
A semidiameter correction is applied to observations of...
单项选择题A semidiameter correction is applied to observations of（）.
A.Mars B.the Moon C.Jupiter D.All of the above
A phase correction may be applicable to correct the sex...
单项选择题A phase correction may be applicable to correct the sextant altitude correction of（）.
A.any star B.the Sun C.third magnitude stars only D.some planets
