Dip needle, engraved “E S Ritchie & Sons”. Case label marked US navy Bureau of Ships. Made by C G Conn Ltd, Elkhart, Indiana.Azimuth circle, marked E S Ritchie & Sons, Pembroke, Mass.
Engineer’s transit signed W&LE Gurley No. 9556. I use this for finding local magnetic variation ashore, and for finding the true bearing of city streets. The sun or a star is used to align the transit circle to true North and South.
Globe Hilsenrath azimuth computer. Not a computer in the modern sense, more like a slide rule. It solves for azimuth, using declination, latitude, and local hour angle or local apparent time. The only slide rule type device which solves for time azimuth, as far as I know. There are slide rules which solve for altitude azimuth, but those are not convenient for compass adjusting.
London Polaris, a specialized type of pelorus which solves for azimuth mechanically. It’s an equinoctial sundial, adjustable for latitude. The latitude scale is under the upper dial, which tilts accordingly. This dial is marked with the hours of the day, and 360 degrees, each degree with a value of four minutes of time. The sight vanes are set to the local apparent time, and the whole is rotated to line up the sun’s shadow. When adjusted for time and latitude, the upper dial is on a parallel plane with the earth’s equator, and the pointer points to geographical North. The pointer can be adjusted to the local variation, so that the dial indicates the magnetic heading based on the sun’s azimuth but without having to solve for azimuth.
another view of the London Polaris
Field’s pelorus, signed J M Fields, San Francisco. Used with shore bearings or the sun with the sight vanes as a shadow vane and also has a shadow pin.
Pocket magnetometer, very convenient for adjusting the heeling magnet
US navy azimuth instrument, Mark II model 3, dated 1942, which is probably the date of the contract let to National Electrical Machine Shops, the maker. I bored a hole in the frame to fit the center pin of C.Plath and Cassens & Plath compasses. It works much the same as the standard navy azimuth circle, with reflecting mirror and prism.
The navy azimuth instrument fitted onto a C Plath compass
testing rig for azimuth circles, for testing the adjustment of mirror and prisms. Nicely made, I suspect that it was made by Northwest Instrument Co., Seattle
