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.