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HM Nautical Almanac Office: NavPac 4.1


If you have any questions or comments about NavPac that are not answered here please use our feedback form to get in contact with us.

Q) Is NavPac available for operating systems other than Windows?

NavPac runs under the Microsoft Windows™ operating system, (version 8 or 10). Unfortunately at this time we are unable to offer NavPac on other operating systems, including the option of running as a mobile application. We hope to be able to develop our range of celestial navigation software in the future. In the meantime, if there is something you would particularly like us to develop, do contact us via our feedback form.

Q) Why does NavPac 4.1.1 only have data up to 2025?

HM Nautical Almanac Office calculates the compact data used in the NavPac software every five years. This keeps the data accurate as the values of ΔT, a measure of the difference between a time scale based on the rotation of the Earth and an idealised uniform timescale at the surface of the Earth, are not predicted far into the future. Our page explains some of the difficulties with predicting ΔT. Additionally, underlying theories and ephemerides of astronomical objects improve over time and by updating our book and software every five years we can assure users they are getting the most up to date and accurate data.

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Last modified: Wednesday, 27 May 2020 at 17:37:06 BST