A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Francis Upchurch
Date: 2016 Feb 3, 06:12 -0000
I would love to know more about how it works . However, I must not try to make a replica! Far too precision engineered for my limited skills. My cylindrical slide rules good for 1-2’ and take 2 mins to get Hc, but then have to plot it to get actual position.
Now here is an interesting navigation slide rule - and 3D too... The Astra-Plot a "three dimensional slide-rule" for celestial navigation, 1969
According to the writeup:
Five specific data to specify the location of a ship
The device specifies the location of a ship to within one nautical mile without the need of any paper calculations. Five specific data are required: First, the approximate position of the ship as determined by the compass bearing and travel time; second, the height of a star above the horizon, preferably the sun, as measured by a sextant; third, the exact compass direction of that star as determined by an amplitude compass; fourth, its hour angle as determined by the time of day and a nautical chart and, fifth, the angular distance of the star to the celestial equator as determined by the nautical chart or the star map.
(415_415_astra-plot_20131125-.jpg: Open and save)