CelestialNavigation.wl (65.1 KB)
DOWNLOAD-DESKTOP-NOTEBOOK.nb (19 MB)
SextantFigures.wl (199 KB)
SextantInteractive.wl (16.4 KB)
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Absolutely brilliant!
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Thank you! This is one of these “old skills” that I always found fascinating. I have anohter “addendum”, but for some reason the interface in the community does not allow me to post it.
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A companion you can hold in your hand: a paper almanac + sight-reduction handbook
In my opinion you should strive to always have access to Wolfram at all times, but I do understand that if you happen to be stranded on a desert island having a working laptop and a good internet connection might not always be possible.
So, after posting this, one detail kept nagging at me. The whole method leans on a nautical almanac, which here is replaced by the package’s equations — so I wondered whether those same equations could simply generate an almanac. After publishing the post I asked Claude (Anthropic’s Claude Code) to build one with the Wolfram Language, produced entirely from the ephemeris in this package rather than copied from any published table.
I was genuinely impressed by the result, so I’d like to make it available to everyone here.
The Sextant Navigator’s Almanac & Sight-Reduction Handbook (2026) — a 123-page PDF containing:
- a handbook deriving the trigonometry to reduce a sight on paper (the circle of equal altitude, the Marcq St-Hilaire intercept, latitude by a noon sight), with three fully worked examples;
- hourly GHA & Declination of the Sun for all of 2026;
- hourly GHA Aries, plus the SHA/Dec of the 58 navigational stars;
- dip, refraction, semi-diameter, and increment correction tables.
Every figure is computed with the Wolfram Language from published astronomy (IAU precession, Meeus’s lunar theory, the ESA Hipparcos catalogue) — end-to-end accuracy about one arcminute. The values were independently cross-checked and agree to a fraction of an arcminute.
It is an educational resource, and the first page says so plainly: it is not for sole-means navigation at sea — for real voyages use an official Nautical Almanac and cross-check every figure. Free to download and share under CC BY 4.0.
Download (PDF):
I’d love to hear if anyone tries reducing a real sight with it.
SextantAlmanac2026.pdf (606 KB)
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– you have earned Featured Contributor Badge 
Your exceptional post has been selected for our editorial column Staff Picks http://wolfr.am/StaffPicks and Your Profile is now distinguished by a Featured Contributor Badge and is displayed on the Featured Contributor Board. Thank you!
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