"Focal length" Quotes from Famous Books
 ... was merely a large collector of moonlight, which was thrown after collection onto a lunium plate. The resultant emanations were turned into a parallel beam by a parabolic reflector and focused, through a rock crystal lens with an extremely long focal length, onto ...
— Astounding Stories of Super-Science April 1930 • Various
... of Cambridgeport, Boston, Mass. One of their most famous telescopes is the great Lick Refractor now in use on Mount Hamilton in California. The diameter of this object-glass is thirty-six inches, and its focal length is fifty-six feet two inches. A still greater effort has recently been made by the same firm in the refractor of forty inches aperture for the Yerkes Observatory of the University of Chicago. The telescope, which is seventy-five feet in length, ...
— The Story of the Heavens • Robert Stawell Ball
... 5 or 6 in. in length; after working 5 hours hold the speculum in the sunshine and throw the rays of the sun onto a paper; where the rays come to a point gives the focal length. If the glass is not ground enough to bring the rays to a point within 5 ft., the coarse grinding must be continued, unless a longer focal length ...
— The Boy Mechanic: Volume 1 - 700 Things For Boys To Do • Popular Mechanics
... of reproduction is equal for two different colours, i.e. this constant is achromatized. For example, it is possible, with one thick lens in air, to achromatize the position of a focal plane of the magnitude of the focal length. If all three constants of reproduction be achromatized, then the Gaussian image for all distances of objects is the same for the two colours, and the system is said to be in "stable ...
— Project Gutenberg Encyclopedia
... simple construction. The essentials of a good stand camera are that it shall be rigid, possess a rising and falling front, a swing back, and bellows which will be capable of extension to fully double the focal length of the lens to be used ...
— How to Observe in Archaeology • Various |
