I'm going to bring my Sextant.

[navybankerteacher]

4 hours ago, Toofarfromthesea said:

 

Sounds both cool and fun.  I bet after a few days one or another of the ships officers will wander by to kibbitz, and maybe give you some tips.

I wonder how many ships officers currently sailing would be of much help.

[ldubs]

I don't understand the couple of references to not being dark enough.   How does darkness come into play with a noon fix?

[chengkp75]

8 hours ago, navybankerteacher said:

I wonder how many ships officers currently sailing would be of much help.

Or would care.

8 hours ago, ldubs said:

I don't understand the couple of references to not being dark enough.   How does darkness come into play with a noon fix?

Not for a noon fix, but for shooting stars at twilight, the more accurate celestial navigation position finding method.

[shipgeeks]

During Vietnam, Mr. Shipgeeks was Navigator on a US Navy ammunition ship.  In 22 months, we steamed 96,000 miles, with a sextant being the only navigational aid.  For shooting stars, the general procedure was 20 minutes before sunrise and 20 minutes after sunset.  We needed a good horizon.

[navybankerteacher]

47 minutes ago, shipgeeks said:

During Vietnam, Mr. Shipgeeks was Navigator on a US Navy ammunition ship.  In 22 months, we steamed 96,000 miles, with a sextant being the only navigational aid.  For shooting stars, the general procedure was 20 minutes before sunrise and 20 minutes after sunset.  We needed a good horizon.

It has to be dark enough for there to be enough visible stars to be able to identify the specific star - which is difficult when only one or two might be visible, yet still light enough for you to clearly see the horizon to be able to use the sextant to "bring that star down" to the horizon ----at which point you can read its elevation on the arc of the sextant.

[whogo]

On 7/11/2022 at 11:31 PM, ldubs said:

Other than that, the discussion of technical aspects of using a sexton is like a foreign language to me.

Using a sextant and using a sexton are two different things.

[John Bull]

1 hour ago, whogo said:

Using a sextant and using a sexton are two different things.

 You deserved that, Idubs 😉

 

JB 🙂

[Heidi13]

4 hours ago, shipgeeks said:

During Vietnam, Mr. Shipgeeks was Navigator on a US Navy ammunition ship.  In 22 months, we steamed 96,000 miles, with a sextant being the only navigational aid.  For shooting stars, the general procedure was 20 minutes before sunrise and 20 minutes after sunset.  We needed a good horizon.

 

I'm surprised that you didn't have at least a LORAN system, as we had a Decca system on most of the ships, even the couple of cargo ships I sailed on.

 

On SS Oriana, we had one of the first SatNavs on commercial ships, but at the time it was the equivalent of a mainframe computer, requiring a computer ticker tape to turn it on and program it. As a cadet, we could look at it, but not touch. We only got to use the sextants and the Decca/RDF when in coastal waters.

[ldubs]

3 hours ago, whogo said:

Using a sextant and using a sexton are two different things.

 

Oh boy.  I can't even blame it on auto-correct.  

[chengkp75]

43 minutes ago, Heidi13 said:

I'm surprised that you didn't have at least a LORAN system, as we had a Decca system on most of the ships, even the couple of cargo ships I sailed on.

Yeah, all the cargo ships I was on in the 70's had the truly archaic LORAN A, and DECCA (heck, DECCA was used for the Normandy landings).

[SimplyMarvie]

15 hours ago, navybankerteacher said:

I wonder how many ships officers currently sailing would be of much help.

 

Probably more than you'd think! We toured a US Naval Destroyer recently, and they still not only had a sextant, but the Navigator talked effusively about how she used it regularly and was currently coming second in an informal competition about being the best at it. 

[chengkp75]

35 minutes ago, SimplyMarvie said:

 

Probably more than you'd think! We toured a US Naval Destroyer recently, and they still not only had a sextant, but the Navigator talked effusively about how she used it regularly and was currently coming second in an informal competition about being the best at it. 

And, I hate to say it, but there are enough people on a bridge watch in the Navy, that she had the time to waste using a sextant.  A commercial ship's bridge, even a cruise ship, while still fairly relaxed, is busy enough to keep the watchstanders busy.  While I believe that knowing how to fix a position by the stars or sun is important for mariners to know, the reality is that it is relegated to their own personal time to maintain competency.

[navybankerteacher]

2 hours ago, SimplyMarvie said:

 

Probably more than you'd think! We toured a US Naval Destroyer recently, and they still not only had a sextant, but the Navigator talked effusively about how she used it regularly and was currently coming second in an informal competition about being the best at it. 

Interesting that the Navigator was effusive about coming in SECOND — I suppose there must have been a couple of old hands who kept their skills tuned on a voluntary basis.  Rapidly plotting star fixes (at least a full semester course in NROTC and the Academy) is an activity which improves with frequent practice.  Captains tended to not be overly patient.

[TheOldBear]

21 minutes ago, navybankerteacher said:

Interesting that the Navigator was effusive about coming in SECOND — I suppose there must have been a couple of old hands who kept their skills tuned on a voluntary basis.  Rapidly plotting star fixes (at least a full semester course in NROTC and the Academy) is an activity which improves with frequent practice.  Captains tended to not be overly patient.

Probably the winner was an old QM or BM Senior Chief

[chengkp75]

39 minutes ago, TheOldBear said:

Probably the winner was an old QM or BM Senior Chief

Yep, since they are the ones who usually take the sights.

[JRG]

10 hours ago, navybankerteacher said:

It has to be dark enough for there to be enough visible stars to be able to identify the specific star - which is difficult when only one or two might be visible, yet still light enough for you to clearly see the horizon to be able to use the sextant to "bring that star down" to the horizon ----at which point you can read its elevation on the arc of the sextant.

 

But you know to look for Venus in the early dusk sneaking out behind the moon,  and because its supposed to be the brightest planet you take your chances...

 

But what are the steps to read the elevation on the arc of the sextant.,  Does that mean that you are looking through the viewer and adjusting the arc until it is in best focus,  or how do you dial it in and I am assuming that the elevation is marked on the arc and when it is in focus that is one of the components of the time and location calculation,   (thats why people look at their watch),  so they have the time (presumably) and the elevation marked, what comes next.

 

What is the calculations,  it should be basic geometry....

 

How about a primer or the process?

 

[shipgeeks]

You are correct.  Besides my sextant, I had an SPS Radar-10.  Ours was the first ammunition ship since WW2 to go through a minefield, Haiphong Harbor.

[chengkp75]

32 minutes ago, JRG said:

 

But you know to look for Venus in the early dusk sneaking out behind the moon,  and because its supposed to be the brightest planet you take your chances...

 

But what are the steps to read the elevation on the arc of the sextant.,  Does that mean that you are looking through the viewer and adjusting the arc until it is in best focus,  or how do you dial it in and I am assuming that the elevation is marked on the arc and when it is in focus that is one of the components of the time and location calculation,   (thats why people look at their watch),  so they have the time (presumably) and the elevation marked, what comes next.

 

What is the calculations,  it should be basic geometry....

 

How about a primer or the process?

 

Stars are located using tables, given your "assumed" position, it will give the altitude and azimuth of the star you are looking for.  Adjust the sextant to the altitude and use the pelorus of the compass to determine azimuth.  The sextant has a mirror that is split, with one half mirrored, and one half clear.  The mirrored half you will see the star, and the clear half is looking at the horizon.  You then adjust the arc of the sextant to "bring the star to the horizon", meaning you will see the star in one half of the mirror, with the bottom of the star on the same level as the horizon.  This gives you the actual altitude of the star at your position.

 

While it is basic spherical trigonometry to calculate the position, the formulas deal with your assumed position, the time of the sight (typically you start a stopwatch when the sight is made, so you can back off that much time from when you check the clock in the chartroom and start calculations), the altitude of the sight, the almanac to show the exact position on earth that the star is directly over at that time, and a set of tables or a calculator to perform the trigonometric equations.  

 

Wiki can give you a quick and dirty primer on celestial.

[wcook]

There are apps for your phone that can help with all the calculations. Of course your phone also has GPS which is 10x more accurate than the best celestial navigation, but where’s the fun in that?

[MBP&O2/O]

My old one ... to help people to get to grips with the descriptions. 

 

[navybankerteacher]

15 hours ago, JRG said:

 

But you know to look for Venus in the early dusk sneaking out behind the moon,  and because its supposed to be the brightest planet you take your chances...

 

…

 

While Venus is easier to locate in the sky, it’s very size requires greater care in “bringing it to the horizon” precisely — and the moon, in particular, the easiest to find, requires bringing just its “lower limb” to touch the horizon 

[CPT Trips]

On 7/13/2022 at 3:14 PM, navybankerteacher said:

Interesting that the Navigator was effusive about coming in SECOND — I suppose there must have been a couple of old hands who kept their skills tuned on a voluntary basis.  Rapidly plotting star fixes (at least a full semester course in NROTC and the Academy) is an activity which improves with frequent practice.  Captains tended to not be overly patient.

I’m acquainted with several grads (circa 2005-10) of Canoe U that were clueless when handed a sextant, so I searched and found that Middies routinely only get a limited survey in celestial nav. 
https://oceannavigator.com/naval-academy-revives-only-limited-celestial/

 

 

 

[TheOldBear]

1 hour ago, CPT Trips said:

I’m acquainted with several grads (circa 2005-10) of Canoe U that were clueless when handed a sextant, so I searched and found that Middies routinely only get a limited survey in celestial nav. 
https://oceannavigator.com/naval-academy-revives-only-limited-celestial/

 

 

 

I went through OCS - not Canoe U - and as I recall the OCS Celestial Navigation syllabus took at most 5 or 10 minutes, and Surface Warfare Officer school not that much longer, even in pre GPS days [1980].

The SWO focus was on LORAN-A and -C with some pre GPS satellite assistance, the Navy 'Transit' system. 

Piloting, maneuvering boards and charts were covered with more time and hands on experience. Oddly this also included use of a sextant - determining distance from objects of known position and height [like lighthouses]. Useful to back up radar fixes, or when emcon prohibited use of radar.

[Heidi13]

3 hours ago, CPT Trips said:

I’m acquainted with several grads (circa 2005-10) of Canoe U that were clueless when handed a sextant, so I searched and found that Middies routinely only get a limited survey in celestial nav. 
https://oceannavigator.com/naval-academy-revives-only-limited-celestial/

 

 

That's the reason we only spent 6 months at college learning to pass the exams, but 2 to 3 years at sea, as a cadet, learning how to do the job.

 

Yes, we learned the theory of celestial navigation at college, but how to use a sextant proficiently while at sea. You just can't experience and learn how to manage all the challenges of celestial navigation in a classroom.

[navybankerteacher]

35 minutes ago, Heidi13 said:

 

That's the reason we only spent 6 months at college learning to pass the exams, but 2 to 3 years at sea, as a cadet, learning how to do the job.

 

Yes, we learned the theory of celestial navigation at college, but how to use a sextant proficiently while at sea. You just can't experience and learn how to manage all the challenges of celestial navigation in a classroom.

Precisely - hands on sighting followed by calculation and plotting takes time to master -- especially if it is to be completed in a reasonable time frame.

 

I was surprised to learn how Annapolis, OCS and NROTC have so completely moved away from celestial --- I guess there is a certain assumption that artificial satellites (and their apps) will NEVER fail.