People's Pilot, Volume 3, Number 5, Rensselaer, Jasper County, 21 July 1893 — POWER OF TELESCOPES. [ARTICLE]

POWER OF TELESCOPES.

Comparative Figures Showing the Weak neu» of the Human-Eye. . The following careful -statement by Prof. E. S. Holden on the power of the eye and the telescope as they-are contrasted in actual experience, is of special and permanent interest: If the brightness of a star seen with the eye alone is one, with a two-inch telescope it is 100 times as bright; with a fourinch telescope it is 400 times as bright; eight-inch telescope it is 1,600 times as bright; sixteen-inch telescope it is 6,400 times as bright; thirty-two-inch telescope it is 25,600 times as bright; thirty-six-inch telescope it is 32,400 times as bright. That is, stars can be seen with the thirty-six-inch telescope which l are 30,000 times fainter than the faintest star visible to the naked eye. While the magnifying power which can be successfully used on the five-inch, telescope is not above 400, the thirty-six-inch telescope will permit a magnifying power of more than 2,000 diame ters on suitable objects, stars, for example. This power cuzaot be used on the moon and planets with real advantage for many reasons, but probably a power of 1,000 or 1,500 will be the maximum. The moon will thus appear under the same conditions as if it were to be viewed by the naked eye at a distance of, say, 200 miles. This is the same as saying that Objects about 800 feet square can be recognized, so that no village or great canal or even large edifice can be built on the moon without our knowledge. Highly organized life on the moon will make itself known in this indirect way if it exists. If one were looking at the earth under the same conditions, the great works of hydraulic mining, or the great operations of Dakota farms or California ranches would be obvious.