9 . Junior officers . must exert themselves to aid in navigation of the vessel . must use solar and stellar observation; both for correction of compass and ascertaining the position of the vessel.
12.
NASA said stellar observations were picking up as the shuttle and its seven-member crew, including four astrophysicists, passed the one-fourth point in a marathon flight of 15 1 / 2 days.
13.
Eratosthenes's results were confirmed by a comparison of stellar observations at Alexandria and Rhodes, carried out by Posidonius in the 1st century BC . These measurements were widely known among scholars, but confusion about the old-fashioned units of distance in which they were expressed had led, in Columbus's day, to some debate about the exact size of the Earth.
