OCR Text |
Show View From Hlnh Points. At mountain stations, where one,ta above the greater part of the lower, dust-laden layers of the atmosphere, moro stars are visible than nt sea level. Some recent observations at Mt. Wilson by Van der Hilt show that the limit of unaided vision there, without with-out even the aid of screens to shut off the light of the sky, at about tho seventh magnitude that Is, the faintest stars that can ho seen on the mountain are two and one-half times brighter than can be seen at sea level. |