" In
another place, speaking of the sun, he says that an object glass of
only two inches will exhibit a curdled or marbled appearance over the
whole solar disk, caused by the intermixture of spaces of different
brightness. And I may add here that Dawes recommends a small aperture
for sun work, including spectroscopic examinations, he himself, like
Mr. Miller, our librarian, preferring to use for that purpose a four
inch refractor.
As you know, the North Star is a most beautiful double. Its companion
is of the ninth order of magnitude, that is, three magnitudes smaller
than the smallest star visible to the naked eye on a dark night. There
was a time when Polaris, as a double, was regarded as an excellent
test for a good three inch telescope; that is any three inch
instrument in which the companion could be seen was pronounced to be
first-class. But so persistently have instruments of small aperture
been improved that that star is no longer an absolute test for three
inch objectives of fine quality, or any first-rate objective exceeding
two inches for which Dawes proposed it as a standard of excellence, he
having found that if the eye and telescope be good, the companion to
Polaris may be seen with such an aperture armed with a power of
eighty.
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