GB821466A - Optical navigational device - Google Patents

Abstract

821,466. Navigational instruments. PIERCE, M. R., and ZUCKERMAN, T. E. Jan. 16, 1957 [Jan. 17, 1956], No. 1689/57. Class 97(2) An optical navigational device comprises means for providing a representation of a point, representing an assumed position, as on a universal plotting sheet, and superposed thereon, an optical image of an observed celestial body displaced from said point in a direction corresponding to the azimuth direction of said body from the navigational device and by an amount representing the difference between computed and observed altitudes of the body. In the form shown, Fig. 12, light from a star is received through a double Dove prism 23, 24, which is rotated, by coarse and fine adjustment means, not shown, to the estimated altitude of the star about a horizontal axis in the common hypotenuse face. A telephoto lens 30, 30<SP>1</SP> images the star, after reflection of the light beam by a mirror 31, in a focal plane 32 if a pivoted mirror 33 is removed from the light path. Superposed on the image of the star, by means of a partially reflecting mirror 101, is the image, produced by a lens 44, of an illuminated graticle 41 which carries an azimuth circle 5<SP>1</SP>, a longitude line 7<SP>1</SP> and latitude lines 8<SP>1</SP>, 9<SP>1</SP> and 10<SP>1</SP> spaced at one degree intervals which are imaged respectively at 5<SP>11</SP>, 7<SP>11</SP>, 8<SP>11</SP>, 9<SP>11</SP> and 10<SP>11</SP>, Fig. 2, the intersection 6<SP>1</SP>, imaged at 6<SP>11</SP>, representing the estimated position of the star. Two wires 3<SP>1</SP>, 4<SP>1</SP>, which are actually adjacent the graticule 41, are imaged at 3<SP>11</SP>, 4<SP>11</SP> to form meridians and are at a spacing adjustable to correspond to the latitude. For this purpose they are carried by members 47, 48 slidable on guides 53, 54 and are actuated by a rotatable knob, not shown, graduated in terms of latitude and carrying projections engaging slot 61, 62 in the respective members. A fixed wire 2<SP>1</SP> is imaged at 2<SP>11</SP> to form an azimuth line. The wires are all fluorescent and are illuminated by an ultra-violet source 51. Also imaged in the focal plane, using a half-silvered mirror 100, is a line 1<SP>1</SP> on a plate 77 adjustable by a screw 85. The image 1<SP>11</SP> is moved by adjusting the screw, to align it with the observed star position 13<SP>11</SP> and so becomes a line of position. A bubble 88 may be imaged at 88<SP>11</SP> for correction purposes. The composite image may be viewed, with the mirror 33 in the position shown, through an erecting prism 92 and eyepiece 91. When the mirror is lifted, as by a reflex camera mechanism, the image may be photographed in the plane 32 using a focal plane shutter. U.S.A. Specification 1,653,585 is referred to.