He
learns what himself and his instruments can do, and he keeps to that
narrow path.
"He was at that time much interested in celestial photography.
"Italy must be the very paradise of astronomers; certainly I never saw
objects so well before; the purity of the air must be very superior to
ours. We looked at Venus with a power of 150, but it was not good.
Jupiter was beautiful, and in broad daylight the belts were plainly
seen. With low powers the moon was charming, but the air would not bear
high ones.
"Father Secchi said he had used a power of 2,000, but that 600 was more
common. I have rarely used 400. Saturn was exquisite; the rings were
separated all around; the dusky ring could be seen, and, of course, the
shadow of the ball upon the ring.
"The spectroscopic method of observing starlight was used by Secchi as
early as by any astronomer. By this method the starlight is analyzed,
and the sunlight is analyzed, and the two compared. If it does not
disclose absolutely what are the peculiarities of starlight and
sunlight, relatively, it traces the relationship.
"In order to be successful in this kind of observation, the telescope
must keep very accurately the motion of the earth in its axis; and so
the papal government furnishes nice machinery to keep up with this
motion,--the same motion for declaring whose existence Galileo suffered!
The two hundred years had done their work.
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