单项选择题
A.cluster B.shower C.constellation D.galaxy
A first magnitude star is（）.A.2.5 times as bright as a ...
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
A double star is a star that（）.A.has a declination equa...
单项选择题A double star is a star that（）.
A.has a declination equal to twice that of the Sun B.comprises two stars that appear close together C.is twice as bright as a single star D.suddenly becomes much brighter and then fades
A correction for augmentation is included in the Nautic...
单项选择题A correction for augmentation is included in the Nautical Almanac corrections for（）.
A.the Sun B.the Moon C.Venus D.None of the above
