The Navigation Spreadsheets suite is available for free download:
Almanac spreadsheets in 2023
Comparisons with the 2023 Nautical Almanac Commercial Edition show that our spreadsheets remain sufficiently accurate for the year 2023 without the need for any changes or updates in the calculations.
Almanac spreadsheets in 2022
Comparisons with the 2022 Nautical Almanac Commercial Edition show that our spreadsheets remain sufficiently accurate for the year 2022 without the need for any changes or updates in the calculations.
Note: difference up to 0.6′ in the SHA of the star Rigil Kent. can be seen in the aries_stars.xls spreadsheet when compared to the printed almanac.
Almanac spreadsheets in 2021
Comparisons with the 2021 Nautical Almanac Commercial Edition show that our spreadsheets remain sufficiently accurate for the year 2021 without the need for any changes or updates in the calculations.
Spreadsheets aries_stars.xls and what_star.xls were modified with the changed spelling of one star’s name (Alnair). Archive TAR and ZIP files were also updated accordingly.
Almanac spreadsheets in 2020
Comparisons with the 2020 Nautical Almanac Commercial Edition show that our spreadsheets remain sufficiently accurate for the year 2020 without the need for any changes or updates.
Lunar distance presetting
Today I conducted a quick exercise presetting a sextant to the Sun-Moon near-limb distance (no refraction corrections).
Sextant: Astra III Professional with the 7×35 Celestaire telescope
Calculations with Navigation Spreadsheets (screenshots attached)
Date: May 26, 2019
Local time: 9:25 am, U.S. Mountain Daylight Time
Universal Time: 15:25
Location: 35° 53’ N, 106° 19’ W
Sun:
GHA: 51° 59.4’
Dec: N 21° 08.8’
SD: 15.8’
Moon:
GHA: 137° 19.1’
Dec: S 13° 17.7’
SD: 14.8’
HP: 54.3’
Topocentric lunar distance: 91° 07.0’
Subtracting the sum of the two semidiameters: 30.6’
Presetting the sextant to: 90° 36.4’
Then, I pointed the sextant at the Moon and soon the Sun appeared right on top of Moon’s limb, as expected. I did not even check the index error beforehand (the sextant has been sitting in its box for months). The whole procedure lasted less than 15 minutes; doing this write-up took somewhat longer than that. 🙂 A good result overall.
Astron 2.00 release
In 2015 “an anonymous benevolent user” of the original Navigation Spreadsheets combined several of them into a single unit named Astron to provide a much more user friendly interface and functionality.
In 2018 version 2.00 has been rewritten as a web page and can be run online on recent versions of popular browsers and, for seafarers, can also be run offline with Chrome, Firefox, and Opera.
https://friendsofthevigilance.org.uk/Astron/Astron.html
Coding in Javascript has enabled some improvements and additions. There is now a sky map addition to the Planner section, a sight log, a sight plotter, and an extended lunar section. Future developments are only intended for version 2.
Extensive user notes can be accessed from
https://friendsofthevigilance.org.uk/Astron/
(Note: both links were updated on July 22, 2020.)
Almanac spreadsheets in 2019
Comparisons with the 2019 Nautical Almanac Commercial Edition show that our spreadsheets remain sufficiently accurate for the year 2019 without the need for any changes or updates.
Almanac spreadsheets in 2018
Comparisons with the 2018 Nautical Almanac Commercial Edition show that our spreadsheets remain sufficiently accurate for the year 2018 without the need for any changes or updates.
Almanac spreadsheets in 2017
Comparisons with the 2017 Nautical Almanac Commercial Edition show that our spreadsheets remain sufficiently accurate for the year 2017 without the need for any changes or updates.
New releases and updates
In 2015 “an anonymous benevolent user” of the original Navigation Spreadsheets combined several of them into a single unit to provide a much more user friendly interface and functionality. The result (named “Astron“) is hereby released with its creator’s consent.
To download, visit:
During this development process a small error (less than 1’) in the GHA calculation was discovered and corrected in all almanac spreadsheets. We therefore recommend downloading the latest version of the suite; in particular, the spreadsheets: aries_stars, sun, mercury, venus, moon, mars, jupiter, saturn, uranus, neptune, what_star, polaris, polaris_lha.
Navigation Spreadsheets 