# Celestial Navigation



## 411353 (11 mo ago)

Do any of you guys serving at sea today still use the sextant and celestially navigate, or is that now a thing of the past?


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## pete8 (Sep 20, 2006)

411353 said:


> Do any of you guys serving at sea today still use the sextant and celestially navigate, or is that now a thing of the past?





411353 said:


> Do any of you guys serving at sea today still use the sextant and celestially navigate, or is that now a thing of the past?



Hi 411353
A good question and a subject that I have often pondered upon myself . An extremely good book which throws some light on this very subject is David Barrie's "SEXTANT". ( 2014) which covers the histories of the instrument and chronometer, and also the navigators who eventually benefitted from the technology. On a personal level, Barrie, in 1973, made a transatlantic voyage in a 3 berth sailing vessel and was taught the rudiments of celestial navigation and the use of the sextant . He makes reference to the demise of the science in the modern world because of global positioning technology which works on the push of a button. But claims that a reaction is setting in " not everyone wants to be completely in thrall to GPS." But I would hazard a guess that perhaps this does not apply to the current professional navigation officer.

Pete


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## John Cassels (Sep 29, 2005)

A most haphazard method of finding one's position.


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## 411353 (11 mo ago)

pete8 said:


> Hi 411353
> A good question and a subject that I have often pondered upon myself . An extremely good book which throws some light on this very subject is David Barrie's "SEXTANT". ( 2014) which covers the histories of the instrument and chronometer, and also the navigators who eventually benefitted from the technology. On a personal level, Barrie, in 1973, made a transatlantic voyage in a 3 berth sailing vessel and was taught the rudiments of celestial navigation and the use of the sextant . He makes reference to the demise of the science in the modern world because of global positioning technology which works on the push of a button. But claims that a reaction is setting in " not everyone wants to be completely in thrall to GPS." But I would hazard a guess that perhaps this does not apply to the current professional navigation officer.
> 
> Pete


Thanks for that reply Pete 8. There is no doubt that GPS is marvelous technology especially if it is of the "differential" variety. The accuracy is almost unbelievable when considering the old traditional methods of navigation.
However from what I recall, when the GPS system was just being built ( _a process which took many years _) , in otherwords it was still in its infancy and was referred to as "Satellite Navigation), it was very restricted geographically speaking.
The system was also a United States designed and operated system in those days, (_and to the best of my knowledge that still maybe the case_), which meant the Pentagon had full control of it. That control was excercised to the full in "war zones" such as the Persian Gulf and areas of the South Atlantic in the vicinity of the Falkland Islands during the hostilities and for some considerable period of time thereafter.
In other words - the Pentagon (_or their agents_) just simply switched the system off when they wanted to.
Whether or not they can still do that today - I have no idea, but I do suspect that they can.
I believe that also was the reason that the European Community entered into building their own satellite navigation system, which if my memory serves me correctly was called "Gallileo". I have no idea how far that project went nor what international "protocols"/"treaties" / "agreements" have been introduced since those early days of building the GPS systems, which may have subsequently effected their development , and the control thereof.


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## Rob Bridger (10 mo ago)

I believe I'm right in saying the US Navy (and others) brought back celestial navigation to their officer training navigation courses a decade or so ago, out of fear that the Russians or Chinese could take out the GPS satellite system.


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## 411353 (11 mo ago)

Rob Bridger said:


> I believe I'm right in saying the US Navy (and others) brought back celestial navigation to their officer training navigation courses a decade or so ago, out of fear that the Russians or Chinese could take out the GPS satellite system.


A very sensible precaution - without doubt.
I clearly recall six stars crossing through the eye of a needle - not much doubt about ones position in such cases.


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## CaptRobert (Dec 29, 2021)

411353 said:


> A very sensible precaution - without doubt.
> I clearly recall six stars crossing through the eye of a needle - not much doubt about ones position in such cases.


I used star sights all the time before Sat available was available, I believe it is still practiced in case the Americans decide to shut it down. I took 8 star sights including Polaris 
Polaris was usually about a mile out to the North of the fix.
The stars position and the noon position did not match up on the the ships speed but when compared between 2 sets of positions gave the same speed of the vessel and usually the course made good.
Needless to say the Chief Officer used to wind the 2nd and 3rd Mates up about there sights being not as good as the star sights. They usually argued otherwise,it was good banter.
I once saw a Chief Officer take star sights right on the limit (or beyond it) of horison visibility which when we had really drifted way off course and would have gone aground!!!
Captain Robert 


,


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## John Cassels (Sep 29, 2005)

Does the previous post not make much sense - or is it just me ?.


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## Lawrie E (Sep 17, 2007)

I retired almost 14 years ago and , for fun, recently took up the Ham-bone again, using a home made artificial horizon.
Sadly, because of adjacent buildings , my back garden sight lines are only available from early Spring to mid Autumn.
But it is great fun and kind of nostalgic in that Google Earth gives me a exact position to several decimal places and it enables me to compare the accuracy of positions obtained by Marc St. Hilaire.

I have been using the "least squares" method of analysing the results and have been pleasantly surprised at what is ,clearly, my own scatter-pattern of accuracy . ....which, doubtless , depends a great deal on both familiarity of using the AA. and the extent to which one is prepared to go to obtain the almanac data, and, especially, the latest info on the most current flavours of the refraction formulae.

It is great fun, I abandoned the old Burtons tables because of making far too many simple errors in extraction, and I went for , what is now considered to be, an elementary level of scientific calculator....four of whose 270 functions I am reasonably proficient.....a doddle really, just ditch the Haversine formula and the CZD and use the Sine and Cosine to find Hc...easy peasy.

It is clear , from the results of my dalliances, that due to slight and, hitherto unknown tectonic shifts, my back garden is waltzing around my part of the Country in a scatter radius which varies between 60 and 1800 feet on any single Position Line. 

Regretfully, using my "water-tray" reflecting type AA, with a home made pyramid style cowl of float glass, I have yet to have any success distinguishing the reflection of Night Stars. I know that the Land Explorers used a bath of quicksilver (Hg) in their AA,s and , presumably, it was much better a reflector.

Being quite taken by the caprice of re-learning all the Math involved, I am now considering learning modern methods of Lunars...would you believe......eat your Heart out Harrison!
Lawrie E


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## Varley (Oct 1, 2006)

The docudrama about 'Longitude' treated The Rev. Nev. very badly. I wouldn't have either with an eaten heart just a few more left-overs on Harrison's table than are usually credited.


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## CaptRobert (Dec 29, 2021)

John Cassels said:


> John Cassels said:
> 
> 
> > Does the previous post not make much sense - or is it just me ?.
> ...


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## CaptRobert (Dec 29, 2021)

John Cassels said:


> Does the previous post not make much sense - or is it just me ?.he


Hi John At that time a merchant vessel usually only had 2 methods of fixing your position once away from sight of land.
Stars could only be taken at twilight when you could see the star and a solid horizon. Usually none or very few clouds.
This window of twilight was about 20 minutes. 

Previously you selected stars in that location lat long from star charts for that covered all maritime locations
They would change over time as on passage Latitude as Longitude changed not dramatically as you have a hemisphere 
of stars.

I took 8 stars which is a bit of an overkill. Using the Lat Long star tables you got a guide azimuth(bearing) and angle above the horizon. You had a special a large scale plotting chart to plot the stars on. 

After a while you just recognised the stars you used.
Using the stars you got a fixed position which was very accurate. Most Chief officers would take 3 or 4.

This gave you a fixed position a bit like taking 8 bearing on the bridge wing compass of lighthouses churches monuments etc. Basically you only took 3 because you knew where you are from he chart. Using radar, decca Navigater, Loran, churchs lighthousess etc backed you in bad visibility. They generally worked well close to land.

In the big oceans you only had the sun and the stars. I did one trip Austailia to Canada 30 days without seeing land.
In bad weather you used dead reckoning to set the course to steer was based on wind speed and estimated force on the ship as well current direction and speed found in the ocean current charts.


The Sun sights are a running fix. You take a bearing of the Sun say 0900 and one at noon.
Noon being when the Sun is bearing due North or South of you. Noon is not 1200 per se
It is when the Sun is North or South of you. this gives you your Latitude.
To give a position you do a running fix. 
This means you take speed of the ship of a towed rotator (mini rotating propeller type thing behind the ship on a very long rope) and gives you the distant covered.
Or a projecting probe underneath the bottom of the hull. It works on a pressure basis.
Off the log you get the speed and off the morning fix a position line.
From the speed you get the distance travelled.
You then move the morning fixed line along the course using the distance travelled.
Then you plot it on plotting chart of latitude and longitude. 
This gives you the noon Position.
In the oceans it gives a good enough position and generally more available to get as the Sun 
Is usually more available than stars.
Stars are more accurate. 
The banter between the Chief Officer (Stargazer) and 2nd and 3rd Mates (Sun chasers)
was all in good fun.
Trust this helps.
Robert


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## Varley (Oct 1, 2006)

Capt. Robert. You are trying to teach Grandma to suck eggs. Although John would willingly see us all rely only on GPS he can navigate the proper way (and I guess may have only practiced that based on when he came ashore) and, no doubt, very well.

(sic transit gloria Mundi - translation: With a satellite constellation one can tell where one is on the gloria mundi more exactly than the charter requires).


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## R798780 (Oct 27, 2004)

CaptRobert said:


> In the oceans it gives a good enough position and generally more available to get as the Sun
> Is usually more available than stars.
> Stars are more accurate.
> The banter between the Chief Officer (Stargazer) and 2nd and 3rd Mates (Sun chasers)
> ...


There was one occassion when the noon fix was at odds to the morning stars. The old man took one look then pointed to the stars fix: "I didn't think we were there anyway". We don't know what went wrong with morning stars, the mate used a stop watch to time his walk to the chronometer, but subsequent fixes showed our noon to be right. I was a first trip 2nd Mate and the mate took me to task -"I heard you use a wrist watch for your sights". He was a tad deflated when I showed said wrist watch. "Nothing wrong with and Omega" I said! (My 21st present).


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## CaptRobert (Dec 29, 2021)

R798780 said:


> There was one occassion when the noon fix was at odds to the morning stars. The old man took one look then pointed to the stars fix: "I didn't think we were there anyway". We don't know what went wrong with morning stars, the mate used a stop watch to time his walk to the chronometer, but subsequent fixes showed our noon to be right. I was a first trip 2nd Mate and the mate took me to task -"I heard you use a wrist watch for your sights". He was a tad deflated when I showed said wrist watch. "Nothing wrong with and Omega" I said! (My 21st present).


I sailed with a Frank Shuttleworth in Common Brothers. Any relation to you? 
.


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## R798780 (Oct 27, 2004)

CaptRobert said:


> I sailed with a Frank Shuttleworth in Common Brothers. Any relation to you?
> .


No relation


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## MMA (Feb 23, 2017)

Stars without Air Navigation Sight Reduction Tables are the stuff of nightmares! The intercepts were large but what the heck! You didn't spend time looking for your chosen stars as it was all pre-computed from the tables. Thus giving you more time to hang over the bridge wing dodgers, ciggie in one hand, coffee in the other!


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## rustytrawler (Jul 6, 2021)

That will be your two of your five a day sorted.


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## R798780 (Oct 27, 2004)

MMA said:


> Stars without Air Navigation Sight Reduction Tables are the stuff of nightmares! The intercepts were large but what the heck! You didn't spend time looking for your chosen stars as it was all pre-computed from the tables. Thus giving you more time to hang over the bridge wing dodgers, ciggie in one hand, coffee in the other!


I used the tables, but also the "Rude" Star Identifier; white plastic disc of the stars, northern hemisphere on one side, southern on the reverse; with clear overlays for the different latitudes. Just position the overlay for the GHA/LHA. It gave you extra choices/chances for those difficult twilights! Working the odd one out longhand was a small price to pay. One other advantage is that planet positions could be added.


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## loco (Dec 10, 2010)

I also used the Rude star identifier, together with sight reduction tables It's still in the loft somewhere, not having been used for forty years or so.......

Polaris in northern latitudes was very handy to get a latitude easily.

My sextant might come in handy should the eclipse prove visible through cloud in a couple of days' time.

Martyn


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## R798780 (Oct 27, 2004)

loco said:


> I also used the Rude star identifier, together with sight reduction tables It's still in the loft somewhere, not having been used for forty years or so.......
> 
> Polaris in northern latitudes was very handy to get a latitude easily.
> 
> ...


Ditto all three, except it was thirty years for the "Rude". Used the sextant to view an eclipse from the car park maybe twenty years ago.


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