NavList:

Re: Geoff's post ( https://navlist.net/Where-World-San-Diego-Hitchcox-jul-2026-g58854 )

On Jul 28th, 2026 , Hoe 10ft / Standard T & P, i.e. 10°C & 1013.25 mb, and:

Sun Declination computed for each time and Sun Ephemeris better than +/- 0.5", and with heights published here-under corrected for only instrument error as follows:

UT1₁ = 01:17:01  / SUNL₁ = 69°22.3'   and UT1₂ = 02:51:02 / SUNL₂ = 52°03.8'

For vessel at anchor (steady position) obtain 03:00 Fix at:

N01°25.4' / E172°58.5' (or: N01°25.37' / E172°58.51')

Thanks for that Antoine (using your more accurate Sun Ephemeris) - I was within 0.1 minutes of lat and lon from your fix.

Normally of course it is the sextant and its use, that are the main error bars of celestial navigation (especially for a hobbyist like me ;-) However, in these contrived puzzles that are perhaps using Stellarium as the "sextant", it is interesting to push ones math methods to the limit - to see if all corrections line up. I find this aspect of Cel Nav most interesting.

Expected actual accuracy better than 0.2' with biggest uncertainty here coming from Atmospheric corrections (Dip, P & T) as usual.

Actual T definitely warmer than 10°C and if reasonably taking T = 25°C and unchanged P at 1013.25 mb, obtain:

N01°25.4' / E172°58.5' (or: N01°25.36' / E172°58.46') with no significant change on Fix here whatsoever.

Thank you for doing that Kermit, that was one of the first things I thought of when reading Joshua's Puzzle. Using the standard atmospheric model (10 degrees centigrade) is a very long way from the 'normal' temperature of the Tarawa Lagoon - having spent 10 days Scuba diving, snorkeling, and swimming there - within a couple of miles from Joshua's puzzle location.

Back 30 years ago, I had one of my most favourite contracts, installing and aligning Geostationary Satellite dishes for the BBC Overseas Service (UK), where I went to many of the tropical islands in the Western Pacific Ocean.

I always used "Celestial Navigation" of the Sun, to aid in approximation of the Azimuth - to point the dish. Before going to each Tropical Island, I precomputed at what time (UTC) the Sun would be to give me the same Azimuth as the Geostationary Satellite. Precise pointing was then achieved using the "Carrier-to-Noise Density (C/N0)" readings of the microwave digital receiver.

It took about two days careful work to assemble and concrete in the dish support and then align. Back then the small plane flights from Fiji, were only every 12 days - so I was 'marooned' on Tarawa with nothing to do but my favourite hobby (back then), scuba diving and exploring tropical waters. My Scuba qualifications seemed to be more important then my Electronic back ground - for these trips ;-) 

So "maybe" I am the ONLY person on NavList, that has swum so close to Jushua's puzzle at Tarawa ;-)

PS: Geoff, did you get my e-mail sent just one hour ago from "here-above" ?

Yes indeed Antoine, and we have exchanged email since then, so all is good - contact made, thank you.

Regards, Geoff Hitchcox, Christchurch, New Zealand.