What are the 4 major contents of the Nautical Almanac?
The Nautical Almanac is an annual publication containing information necessary for navigation by sea. It contains tables giving data such as positions and brightnesses for celestial bodies, including sun, moon, and navigational planets and stars.
It was first published by The British Admiralty in 1767 and is now produced jointly by The United Kingdom Hydrographic Office (UKHO) and United States Naval Observatory (USNO). It is essential for any sailor wanting to accurately navigate at sea.Overview of 4 Major Contents
The Nautical Almanac includes four major components: Tabulations for the Sun, Moon, navigational planets and stars. Each component provides a wealth of information to help determine positions at sea when using a sextant. By plotting this data, sailors can calculate their exact location on Earth. A sailor must have knowledge about each component to accurately navigate at sea. Let’s take a closer look at each one.
SunThe sun’s tabulation provides important information about its position on any given day throughout the year. It includes its declination, hour angle, altitude, azimuth and twilight times for every degree latitude from 0°N to 69°N.
This data enables sailors to calculate their position based on where they observe sunrise or sunset or any point between that on a given day. With this information they can determine longitude by comparing their observations with those listed in tables in the almanac.
MoonThe moon’s tabulation provides similar information to that of the sun’s except it also contains data regarding moonrise or moonset beyond 69°N which is outside the range covered by solar observations. The moon’s data includes its declination, right ascension, altitude, azimuth, semi diameter and its phase (including new moon).
It also includes a lunar distance table which shows angular distances between celestial bodies as viewed from earth at any given time over a period of one month. This enables sailors to calculate their exact latitude on Earth using lunar distances combined with other observations such as altitude readings from a sextant or star sights from special instruments such as an octant or astrolabe.
Navigational Planets & StarsThe almanac contains detailed data regarding navigational planets such as Venus, Mars, Jupiter and Saturn as well as certain navigational stars such as Polaris (the North Star) for both northern and southern hemispheres over a period covering one year from January 1st through December 31st each year.
These tables provide information such as right ascension and declination angles which enable sailors to make calculations based on these readings combined with other observations such as star sights taken with special instruments like an octant or astrolabe which enable them to accurately locate their position on Earth using various methods including dead reckoning or celestial navigation techniques.