Page 360 - 89 history of astronomy_opt
P. 360
partly cut away to admit the light. A di-
vided circle, with pointer and reading mi-
croscope, was provided for reading the dec-
lination. He realised the superiority of a
circle with graduations over a much larger
quadrant. The collimation error was found
by reversing the instrument and using a ter-
restrial mark, the azimuth error by star ob-
servations. The time was expressed in frac-
360
