Sentence Examples with the word photographic film

The peculiar form of the tube is eminently suited for rigid preservation of the relative parallelism of the axes of the two telescopes, so that,;i the image of a certain selected star is retained on the intersection of two wires of the micrometer, by means of the driving clock, aided by small corrections given by the observer in right ascension and declination (required on account of irregularity in the clock movement, error in astronomical adjustment of the polar axis, or changes in the star's apparent place produced by refraction), the image of a star will continue on the same spot of the photographic film during the whole time of exposure.

At the receiving station a cylinder - which revolves synchronously with the transmitting cylinder - is covered with a photographic film or paper, upon a point of which a pencil of light from a Nernst lamp is concentrated.