We see the sun rise in the east each morning and set in the west each evening. This part of the Nautical Almanac is found at the bottom of the right-hand daily page.
In that discussion, however, we used the Copernican model of the sun at the center of the solar system. This location is called the ground position GP. The declination is just a measure of the angle at the center of the Earth formed by the plane of the equator and going out to the celestial body.
We will use the sight reduction tables that will perform the calculations for us. The cockpit offered a full array of instruments which the pilot used to fly the simulated aeroplane. When used this way, a navigator will from time to time measure the sun's altitude with a sextant, then compare that with a precalculated altitude based on the exact time and estimated position of the observation.
The celestial sphere: GHA and declination In the previous paragraphs, we looked at the actual physical forces that govern the motion of the sun through the sky.
Traditionally, a navigator checked his chronometer from his sextant, at a geographic marker surveyed by a professional astronomer. Please help improve this section by adding citations to reliable sources.