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achromatic adjustible mirror angle aperture aplanatic astigmation Bertsch blurs of diffraction centimetres chemical focus chromatic aberration collodion colour concave condenser cone of solar convergent lens convex correcting lens crown-glass diaphragm direction distance distortion divergent double dyalitic apparatus employed enlarged image enlarged proof enlarging apparatus enlarging lens enlarging objective equal exactly face fixed flint-glass focal length focal plane frame give globe-lens green glass ground-glass heliostat horizontal inches in diameter incident ray index of refraction iron Lastly lenses luminous margins meniscus metres millimetres mounting move moveable necessary negative lens oblique optical apparatus opticians ordinary parallel pencils photographic pieces placed plate position prism radiating point radii of curvature rays emergent reflected refracted ray reproduced screen sharp image side single objective solar camera solar light solar rays spherical aberration sun's surface thickness tighten the screw transparent triplet turned vertical wooden
Page 17 - When a ray of light passes from one medium to another, it is refracted so that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the ratio of the velocities in the two media.
Page 225 - ... they should have been previously cut in the house, from the pattern given by one of the cards that had been mounted and cut in the instrument. In mounting the instrument in place, the points to attend to are, (1) that it shall be level as regards east and west, (2) that the axis of the ring shall be inclined to the horizon at an angle equal to the latitude of the place, (3) that the plane passing through the axis of the ring and the meridian line marked on its inside shall be in the plane of...
Page 165 - I f; to properly adjust the negative, J, so that its enlarged image is sharply formed on a screen, placed at a distance and perpendicular to the optical axis of the apparatus, and, lastly, to substitute for the screen a sheet of sensitive paper or other Photographic surface. Considerable improvements have been made in the Solar Camera of Woodward, notably those by Dr. Monckhoven, who, to cure the evils arising from the aberrations of sphericity, whereby the various transmitted rays do not arrive...
Page 59 - Hence the magnification, as thus defined, is measured as before by the ratio of the size of the image to that of the object, when the image is at the least distance of distinct vision.
Page 36 - ... and is perpendicular to the plane surface. A straight line passing through the optical centre, and making an angle with the principal axis, is termed a secondary axis. The centres of curvature are the centres of spheres, of which spheres the surfaces«of the lens are segments.
Page 163 - I (fig. 75), called the condenser, at the principal focus of •which an achromatic objective, L, is fixed. A mirror, AB, throws the solar rays, rr, on the condenser, I ; and the negative, J, moveable by means of a rack, K, is placed between the two lenses at a distance which varies with that of the screen on which the image is to be formed.
Page 67 - The chromatic aberrations. The focal length of a lens is a function of the index of refraction of the material of which the lens is composed. Since the index of refraction of all optical substances varies with wave length, the focal length of a lens is different for different colors. As a consequence, a single lens forms not merely one image of an object, but a series of images at varying distances from the lens, one for each color...