Celestial Navigation - how good were you?

[mawtty]

In the Solomon Sea taking a noonsight, the sun was in the zenith and I could not find a dip. I was within 25 nm of my dead reconning position.
It took me an hour to do a fix with air nav tables and a couple of pages of calculations to get a cocked hat. I could get within 5nm of my position but if the chronometer was out by ten seconds so was my longitude out my 10 nm!!
Tulku Tim the Horrible Hornblower.
These days my cell phone gives me crystal clear charts and a max error of 2 meters.

[rtooh]

I circumnavigated in the early 90s using a sextant (GPS was $5000. Used sextant was $500!). Wasn't very good at the beginning. For instance, when the DR from my last running sun fix said I should be beached on Nuku Hiva, I was actually 30Nm due north. Ouch. And in the Tuamotus I nearly lost the boat. With no wind we were motoring through the night on a full moon. I was in the cockpit on watch but seated against the companionway combing and facing aft. I heard the thunder of the waves crashing against the reef before I saw them. I jumped to my feet and saw the whitewater was dead ahead... really close and really white in the moon's light. My heart stopped. Not sure how much time separated me from a wreck, but my fix said I shouldn't be where I was. Wow! I improved though over time and by the Indian Ocean transit I often had tight bundles of LOPs. I once had a freighter pass concurrent with a evening shot of the stars. I asked for his GPS position and determined my fix was about 3Nm off. I still love the process of navigating by the sun and stars...but I will never again face aft in the Tuamotus.

[Michael Pope]

The most valuable thing I learned from my teacher is : It is not one good sight you need it is a river of sights and other information. A Tamaya calculator makes it less time consuming. So then do your morning stars two sets if you have time record your sunrise if you can see it. Do a moon if you have a good sky and your noon sun of course . but do not neglect any information --where the birds flew at sunset , The funny color reflected on the cloud LOG IT and the routine become a fun game instead of a chore.
and your dead reckoning has to be accurate but a few months with the same boat and it will improve. I was left at sea once with a sextant no time no electrics and a soggy torn chart. after three to four days I could hold a sextant( broken shoulder) and after 11 days I was picked up My plot was closer than 2 miles from Sat Nav on the tug but most of that accuracy was from assessing how far in which direction my celestial sights could be from my dead reckoning and the birds. It becomes an art when you in low islands and reefs.
I drank once with a Destroyer Skipper USN in the Sat Nav era and he said he always trusted his Celestial over the electronics and he had a big room full of them BUT he had three ensigns doing celestial every day from a high stable ship and averaged them and was contented with a mile and a half accuracy.
My first teacher could not find an Island after doubling back and looking
sent me up a sixty five foot mast to look for it-- never saw it-- That was when I started studying it. One Day , Any Day, there may be No gps or it might have moved by Jamming. Kinda nice to know where we are. NO Batteries required! and it can be fun! Kiwi Dickie Jones used to use celestial with a plastic clipboard and a wax crayon from the back of a raceing i/2 Tonner and give you dead on bearings for the next mark in rough weather! AN Art!

[RichMac]

Francis Chichester was a brilliant navigator, in 1931 he flew his little plane from NZ to Norfolk Island. He took sextant readings at a particular time, he had pre-plotted those readings on the chart to get a position line without any calculations. And he intentionally steered to one side of Norfolk, so he knew which way to turn once he'd done the distance.

But, sailing thru the Bahamas in 1971, luck was on his side. The weather was bad and he was exhausted. His DR showed him passing between two islands, and he went to sleep. When he woke up, he had passed between two islands, but the wrong ones! Fortunately his DR error was big enough to safely find another gap.

[slug]

Originally Posted by RichMac

Francis Chichester was a brilliant navigator, in 1931 he flew his little plane from NZ to Norfolk Island. He took sextant readings at a particular time, he had pre-plotted those readings on the chart to get a position line without any calculations. And he intentionally steered to one side of Norfolk, so he knew which way to turn once he'd done the distance.

But, sailing thru the Bahamas in 1971, luck was on his side. The weather was bad and he was exhausted. His DR showed him passing between two islands, and he went to sleep. When he woke up, he had passed between two islands, but the wrong ones! Fortunately his DR error was big enough to safely find another gap.

When using celestial or traditional navigation , position accuracy is unknown..

this unknown causes you to behave in a seaman like manner...you hove too offshore for the night or in the fog .. only when the sun rises or when visual navigation becomes possible do you enter the harbour or pass between islands.

Electronic navigation allows you to disregard seamanship and steam right between the shoals at night, in the fog.

[Michael Graham]

I found the celestial navigation pretty accurate on a voyage Cape Town to Rio to Caribbean to Fort Lauderdale. On a Roberts 53. It was a great confidence builder for a new navigator to find St Helena directly ahead at dawn as expected and I relaxed thereafter.

One day between Fernando de Noronha and St Lucia my overnight DR was found to be way out and I was baffled until we clicked that the Amazon had pushed us way off course overnight even though we were a long way offshore.

[skipperpete]

On my first offshore trip after a year of celestial nav night classes I found Middleton reef after a week of sailing from Coffs Harbour. I was about to give up and aim for Australia again when I saw a ship........ the Sygma , wrecked on the end of the reef. I was out by about 15 miles and from then on never did better than an average of 8-10 miles accuracy despite my best efforts over 15 years but that seemed to be good enough for my needs.

[Bycrick]

With an old Tamaya sextant, I can usually get within 10 miles on a single sight. My usual practice is to take about 10 sights about a minute apart. I’m currently using the Starpath app to reduce the sights and then "averaging" them. That usually results in an LOP that’s within a couple of miles of my GPS. Sun or moon sights only because the combination of old, not so good, eyes and a full-view mirror makes star sights a problem.

[gamayun]

Originally Posted by skipmac

Sounds like navigating to Hawaii in the old days. Never did it myself but heard the plan was to leave California, dead reckon until you're a few days or week out of Hawaii then follow the contrails from the jets flying into Honolulu.

Funny. I heard this recently during an "if all else fails" conversation.

My earliest on the water memory was hoping to get as close as 15 feet to the dive sites off North Florida using Loran-C. Sextants just aren't that very useful for fixing positions under water, but I love hearing these stories on how it can be done (usually) with good accuracy.

[Michael Graham]

I was fortunate enough to be on a stable yacht with an accurate time. In good weather I would expect an accuracy within 3 miles. I once did a test in the Canaries when tied on the outside of the harbour wall and the fix was within 1.5 miles - admittedly cheating with no forward progress between fixes.

We were surprised to find that this was more accurate than the position given simultaneously by the early generation satnav on board. This only picked up a few weak satelite fixes low in the sky.

[skipmac]

Originally Posted by gamayun

My earliest on the water memory was hoping to get as close as 15 feet to the dive sites off North Florida using Loran-C. Sextants just aren't that very useful for fixing positions under water, but I love hearing these stories on how it can be done (usually) with good accuracy.

That was a big deal for a while when GPS was starting take over especially with the initial GPS fixes degraded with selective availability. A lot of boaters, mainly for fishing and diving didn't want to give up Loran, for the accuracy and repeatability but also because they had a collection of Loran numbers for all their favorite spots.

The first time I dove the artificial reef site 25 miles off Clearwater with GPS I had to run a search pattern for about 30 minutes before I finally spotted the wrecks on my fish finder. If I recall my initial GPS fix put me about 1000 yards off the site.

[Uricanejack]

Good enough, I guess.

[Scaramanga F25]

As we approached land we used our RDF back then. Radio Direction Finder.

[belizesailor]

Originally Posted by Uricanejack

Good enough, I guess.

I would put myself in that category to, I could do celestial with a cheat sheet, but never did it enough to get really proficient.

Years ago crossing from Massachusettes to Bermuda we lost GPS signal...gone...no signal received by ship's GPS or the various handheld units aboard. We were about half way across. Fortunately we had been practicing our celestial and plotting our fixes vs GPS to check how we were doing. We completed the rest of the crossing on DR/Celestial only and nail it...good thing, Bermuda is tiny. The channel into Bermuda is well marked and charted so that's easy.

[GordMay]

A U.S. military document from the office of the Chairman of the Joint Chiefs of Staff, CJCSI 6130.01B,
"Master Positioning, Navigation, and Timing Plan"
has this to say:

e. Celestial Navigation. Celestial navigation, as traditionally
practiced, provides an average error in position of 2 nm...

➥ https://apps.dtic.mil/dtic/tr/fulltext/u2/a414737.pdf