October 20, 2020

Declination

Declination.  Declination corresponds to terrestrial latitude and is defined as the angular distance of a heavenly body north or south of the celestial equator, measured in units of arc (ie degrees, minutes and seconds).  Declination is the result of the earth’s movement/orbit around the sun and the fact that the […]
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October 20, 2020

Hour angle

Since the declination gives us the “latitude” of the heavenly body we must now find it’s “longitude”. We do this by measuring the angle between the celestial meridian passing through the body and that running through the observer’s position. The hour angle is defined as “the angle between the meridian […]
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October 20, 2020

Geographical position

Polar Distance. This is the angular distance of a body from the elevated pole (the pole that is above the celestial horizon). This is the distance PX in the sketch. When the elevated pole and the declination have the same names, the polar distance is 90° – declination. When they […]
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October 20, 2020

Sunrise and sunset

Calculating times of sunrise and sunset. The times of the visible rising and setting of the sun are contained in the daily pages of the nautical almanac. They are tabulated for the middle day of the three on that page and provide the Local Mean Time (LMT) of the rising/setting […]
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