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## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Compare Methods: Lat/Lon Near Noon
From: Herman Dekker
Date: 2021 Sep 15, 13:40 -0700

Lat/Lon near Noon one other way to calculate it.

I thought I calculated Frank’s problem by the TI-89 calculator with Starpilot program.

First calculate with CoarseMadeGood and SpeedmadeGood program the result of boat and current movement.

Outcome Course 158° Speed 4,3 Kt

The TI-89 calculator asks the DR position and the HE , for the sight reduction
that is not given so I had to calculate roughly myself.

I am educated by Frank LAT=ZD + Dec. ZD= (90°-Ho)
I choosed the sight with max measured height.
UT 16:39 Hs=73,075° Ho=73,075+0,216=73,291°

Almanac for 22-mai-2022 midday gave about Dec=20,44
Sun shadow points North. So LAT=+ZD + Dec

LAT=(90°-73,291°) + 20,44=37,15° N
Noon is around max. measured height at ~UT=16:39
Converted UT to Lon, at UT 16:39 Lon = 69,75° W
For HE, reverse calculated from given info HE=8,3 feet

Now typed al six sights in the Sight reduction program.
Then simplistic did Fix by computation at UT 16:39:15 and the answer is:
LAT 37°11,4’ N
LON 70° 12,5 W
Even as the lops cross under shallow angles, a good result.

At UT 17:00:00 the position is:
LAT 37°10’N
LON 70°11.8’W

This my contribution on the Noon problem.
HermanD

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