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Some of you may remember William Murdoch's March 1996 Cruising World
article, with its TI-81 Sun-sight programs shoehorned into 2,259 bytes.
I've written a modern, independent take on the same idea, called
SUNSIGHT, for the plain monochrome TI-84 Plus, and released it open
source (MIT):

https://github.com/robmurray-avant/SUNSIGHT-TI84Plus

What it does: enter date, UTC, DR position, Hs, limb, index error,
height of eye, pressure, and temperature, and it returns intercept
(to 0.1 NM) and azimuth — with cautions for a low Sun (below 5°),
a Sun near the zenith (above 87°), and intercepts over 25 NM. It uses
Meeus medium-precision solar algorithms, and I've validated it against
USNO data (mean GHA difference 0.044' across a ten-case 2026–2036 set)
plus the historical Cases A–D. Supported dates: 1900–2049.

Why the TI-84 Plus: cheap second-hand, runs for ages on AAA batteries,
no Wi-Fi, no updates, no phoning home. Its failure modes don't overlap
with GPS or the boat's electrics, which is exactly what a backup is
supposed to provide. And unlike Murdoch's readers, you don't key it in
by hand — it loads via the free TI Connect CE software in a couple of
minutes.

I wrote up the story for my sailing club's magazine here:
https://currents.bluewatercruising.org/article/sun-sights-without-the-almanac/

Confession up front: liberal arts degree, no programming education; I
built this with online tools and AI assistance, so any errors are mine
alone. The repo includes the annotated source, test cases, and a
standard acceptance test (Case A), and independent testing is very
welcome — I'd genuinely like to hear where it breaks.

Fair winds,
Rob Murray
SV Avant