Page:Astronomy for Everybody.djvu/79
steady, so that the heavenly bodies will look sharp when seen through it.
We frequently see calculations showing how near the moon can be brought to us by using some high magnifing power. For example, with a power of one thousand we see it as if it were two hundred and forty miles away; with about five thousand, as if it were forty-eight miles away. This calculation is quite correct so far as the apparent size of any object on the moon is concerned, but it takes no account either of the imperfections of the telescope or the bad effect produced by the atmosphere. The result of both of these defects is that such calculations do not give a correct idea of the truth. I doubt whether any astronomer with any telescope now in existence could gain a great advantage, in the study of such an object as the moon or a planet, by carrying his magnification above a thousand, unless on very rare occasions in an atmosphere of unusual stillness.
Mounting of the Telescope
Those who have never used a telescope are apt to think that the work of observing with it is simply to point it at a heavenly body and examine the latter through it.[1]
- ↑ The writer recalls that when Mr. James Lick was founding the observatory which has since become so celebrated, the great telescope was the only feature which seemed to interest him, and his plan was to devote nearly all the funds to making the largest lens possible. He did not see why such a complicated instrument as that used by astronomers was necessary. The troublesome problem of seeing a heavenly body through a telescope had to be explained to him.