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ADMIRALTY Astronomical Publications

Astronomical information to support marine celestial navigation

Rapid Sight Reduction Tables for Marine (NP303 volumes 1, 2 &3)

​​​Available as a three volume set. Volume 1 is aimed at the navigator using astro-navigation and provides the optimum selection of stars for a three-star fix. Volume 2 covers latitudes between 0° and 40°, with Volume 3 covering latitudes between 39° and 89°.


NavPac and Compact Data (DP330)

​NavPac software enables navigators to compute their position at sea using celestial navigation. It provides methods for calculating the positions of the Sun, Moon, planets and stars to a consistent precision, with the aid of a pocket calculator, personal computer or laptop.

This software package also includes features designed to make celestial navigation easier, including:

  • Functions for calculating great circle and rhumb line tracks, and rise and set times of celestial objects

  • Tools for determining altitudes and azimuths

  • 'Find next phenomena' functionality

  • Additional plotting options

  • Night mode


NavPac is used worldwide by the Royal Navy and by many navigators who require an independent means of navigation.


The Astronomical Almanac (GP100)

A worldwide resource for fundamental astronomical data, the Astronomical Almanac includes contributions from astronomical experts, as well as a wide variety of technical and general astronomical information. This includes:​

  • Positions of the Sun, Moon and planets to milli-arcsecond precision

  • Positions of minor planets and planetary satellites for each year

  • Data relating to Earth orientation, time-scales and coordinate systems

  • Sunrise/set, moonrise/set and twilight times

  • Reference data for stars and stellar systems, observatories and related astronomical constants and techniques.


This is a joint publication with the United States Naval Observatory.


The Star Alamanc (NP321)

The Star Alamanc contains positions of the major and selected bright stars in a tabular format for easy identification. It is ideal for land surveyors who use astronomical observations to determine their geographical position or the direction to true north.


This edition includes:

  • A CD containing the almanac in PDF format and the coefficients representing the positions of the Sun and stars in ASCII files

  • Coefficients for calculating the Greenwich hour angle and declination of all the stars published in The Star Almanac, accurate to about 1 arcsecond

  • Polynomial coefficients for calculating R (GHA Aries - UT), declination, E and semi-diameter of the Sun are also included.


Astronomical Phenomena (GP200)

This publication provides a summary of astronomical events.  It is published several years in advance and contains much of Section A of the corresponding Astronomical Almanac (GP100). 


This publication includes:

  • Phases of the Moon, eclipses of the Sun and Moon

  • Principal occultations, planetary phenomena, elongations and magnitudes of the planets

  • Times of sunrise/set, moonrise/set.

  • Tabulated equations of time, the declination of the Sun and the Greenwich hour angles of the pole stars Polaris and Sigma Octantis