GB475918A - Navigation instrument - Google Patents

Abstract

475,918. Calculating - apparatus. ASHLOCK, E. H. Aug. 18, 1936, No. 22761. [Class 106 (i)] [Also in Group XX] An instrument for determining latitude and longitude or effecting other navigational calculations comprises a circular azimuth indicator 2, Fig. 14, a semicircular altitude arc 3 having a radial aixs of rotation coinciding with axis of the ring 2, a semicircular rotatable latitude indicator 12 with its axis coinciding with a diameter of the ring 2, a circular rotatable longitude indicator 23 with its axis coinciding with the diameter 14 joining the ends of the latitude arc 12, and a semicircular declinationindicator 15 rotatable about a diameter coinciding with the diameter 14. The longitude indicator 23, an hour indicating ring 22 and a star chart 21 are concentrically and rotatably mounted on a plate carried by a bracket to which the latitude arc 12 is secured and which is hung from the main frame (not shown) supporting the ring 2 by pivots aligned with the E-W axis of the ring 2. The adjustment of the various parts is effected by micrometers. The azimuth ring 2 and altitude arc 3 may be separated from the rest of the instrument and fitted on top of a compass 6, Fig. 12, to enable the altitude and azimuth of a celestial body to be determined. A sleeve 9b slidable . on the arc 3 and adjustable by means of the micrometer screw 9g detachably carries an L-shaped sighting tube 10 of which the longer leg 10a extends towards the centre of the ring 2 where the light is reflected by a prism along the shorter leg 10b to a ground glass 10d. The image of the observed body is brought into coincidence with cross wires on the screen 10d. The sighting tube 10 is removed before replacing the ring 2 and arc 3. Alternatively, the altitude and azimuth may be observed independently by a sextant &c. A sleeve, which may be adjusted on the arc 15 to the known declination of the observed body, carries a spring urged centring member which may be brought into register with a co-operating socket on the slide 9b by adjustment of the latitude arc 12 and declination arc 15. Fig. 14 shows the 24‹ 30' graduation on the arc 3 registering with the 12‹ S. graduation on the arc 15, the latitude, 32‹ 40', being indicated by the point at which the ring 2 cuts the arc 12. The longitude indicator 23 when adjusted so that the graduation corresponding to the time of observation, 10-52 p.m., is at the declination arc 15 indicates the longitude, 117‹ W., by the graduation at the uppermost point. The longitude indicator 23, hour indicating ring 22, and star chart 21 are adjusted relatively to each other in accordance with the various time reckonings. Reference has been directed by the Comptroller to Specification 20909 /91, [Class 97].