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Old 17-09-2018, 17:57   #1
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Considering these ideas of navigation.. What is your opnion on it?

I always considered learning celestial navigation to use in case of a gps failure. The satellites not working or my units not working. Thinking of having at least 2 on board.


However I noticed that besides having a sextant, I also need a accurate clock, somehow

know my precise time then a nautical almanac. Probably other things I didnt consider yet.


So I am pondering here.




About the usefulness of it all and from my chair sitting on land I think it is not useful.


Lets see.. If I am in the middle of the atlanctic, crossing to the caribbean and all my gps stops working. I am probably well prepared on food, water.So I just continue going East. Then I just chill? I will hit America or somewhere else.



However if I am in South America with plans to go in Grenada and the gps fails. I just turn South. Then I just chill?


In the middle of the pacific, crossing from Chile to Tahiti or Australia. Gps stops working. I would be super well prepared considering it is a Pacific crossing and the doldrums and all that. So I go North? I would probably hit Japan or something. No way I would go right between the Bering Strait and into the north pole. Right? So just chill?




I would like your opnions on this, I will value it and reconsider my position (ha!), seriously because for now I am considering it is not worth. Thanks a lot.
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Old 17-09-2018, 18:13   #2
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Re: Considering these ideas of navigation.. What is your opnion on it?

So your in the Pacific and you just go north till you hit someplace. That could be 50 days or you could have a cheap sextant and a watch and find the island that's 2 days from you. Seems like a no brainer. And it's nice to learn a new skill.
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Old 17-09-2018, 18:18   #3
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Re: Considering these ideas of navigation.. What is your opnion on it?

Sorry the accurate clock is easy you can get time signals with a cheap battery powered radio and set your Casio watch to that. I would not cross an ocean without celestial as backup.
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Old 17-09-2018, 18:27   #4
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Re: Considering these ideas of navigation.. What is your opnion on it?

"Well, if we get lost, we'll just pull in somewhere and ask directions."

Capt. Ron
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Old 17-09-2018, 18:34   #5
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Re: Considering these ideas of navigation.. What is your opnion on it?

Any boat, anywhere, is one lightening bolt away from the 19th century. Crossing an ocean without some none-electrical way of finding your location is foolhardy.

An inexpensive plastic sextant will be more than adequate, and you do not need to have an almanac for each year, you can use a long term almanac that is good until 2050 (and more, actually) Long Term Almanac

Bullet (and lightening) proof, accurate time keeping is a bit of a challenge. I have a self winding wrist watch that keep running at sea. But of course, people sailed across oceans for hundreds of years without chronometers, so I'll be you can too with a little learning applied.
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Old 17-09-2018, 19:27   #6
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Re: Considering these ideas of navigation.. What is your opnion on it?

Here’s my idea:

Davis Mark3

3 cheap casio watches ($15 each) plus a Molinja pocket watch ($35 or so Ebay)

G.Kolbe Long Term Almanac.

Moon almanac printed on waterproof paper for several years to come including laminated correction tables.

Rite in the Rain notebook

Plotting sheet printed both sides and laminated

Two sun, 1 moon and 3 star worksheets printed together front and back on a single sheet and laminated.

Grease pencils and/or erasable markers in fine point.

A steel cash box to hold the watches, a spare GPS, a small solar battery charger, some NiMH batteries to fit the GPS and some alkaline batteries.

Total cost about $200, excluding the spare GPS





For a week prior to voyage the pocket watch is wound daily at the same time and rate of error are established. The quartz watches are also checked These errors are tracked in the Rite in the Rain. The Casios are NEVER reset, except just after the finish of a voyage where there will be time to recheck the error rate before another voyage starts.

Underway everything is pulled out once a week and a single sight is shot (not a noon sight) and the GPS MOB button is pushed at the same time. The sight is worked and plotted. After the fact the GPS coordinates are retrieved and plotted to give feedback on how close the LOP is to the MOB. Error for each of the timepieces is checked and logged in the notebook.

So then the unpleasantness occurs.

In the worst case the Casios are fried and the Molija was let to run down and time is lost. Wind them and set them to the same time making a best guess as to what the time might be. To regain at least semi-accurate time shoot the moon and a few other bodies. The moon needs to be significantly east or west of your position for this to work well (let’s say 30degrees east or west of true north or true south). You should get some vague agreement among the misc. bodies with the moon line even further out. Add or subtract a set amount of time to all of the sights and recalculate. The rule of thumb is 2 minutes of time for each minute of longitude disagreement between the moon and the ‘fix’ for the other bodies. After the first 2 cycles you should be able to interpolate or extrapolate. If the moon line is to the west add your correction, if east subtract the correction. When the moon agrees with the rest of the fix you have figured out how big the error was for your best guess of time. You have re-established time. Would probably be good to immediately or the next day reshoot a round including the moon and double check the time correction. Thereafter recheck weekly. In a lightning strike I would worry that the high magnetic fields might affect the watches rate of error so that should be tracked over time.



This method of regaining time is not of my own devising, it is from John Letcher’s book on navigating with HO-208, a good read all around though I did not come to adore 208 the way he did.


Here's a free book you can download:

http://www.teacupnavigation.net/Cele...a_Teacup_u.pdf
which was found at
Celestial Navigation

This uses a calculator for the sight reduction, not appropriate if you want to learn to use the tables for sight reduction.

Has a good chapter at the end about how to use a sextant to determine your circle of position by measuring the horizontal angle between two landmarks.

The Mark 3 is not Davis's least accurate sextant. I read a reasoned argument at Strait of Magellan: Celestial Navigation 101 indicating that the Mark 3 is more accurate than the 15 or 25 even new out of the box.

Why go for the cheaper resource for the ditch kit? Several reasons I can see.
A) You don't need great accuracy in a lifeboat except in a very few locations such as the south pacific where the only islands you can hit for thousands of miles are very small. Most places you will have a fairly large target to hit so 15nm either way would be acceptable. Greater accuracy would require greater size and weight in the ditch kit.
B) Minimizing the cost of this item and its ancillary equipment allows you to spend more money on other safety gear to stow in the lifeboat or ditch bag. All told you would need $150 or so for the whole setup including sextant, long term almanac with reduction tables, 3 watches and a good case. That's about the cost of a cheap GPS.
C) The Mark 3 being dirt simple also means there is a lot less to go wrong.
D) The vernier reading helps keep you from developing a false sense of precision about your results. A pity more people can't keep this idea in mind when using the results of their GPS.
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Old 17-09-2018, 19:40   #7
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Re: Considering these ideas of navigation.. What is your opnion on it?

Dead reckoning and pilotage are skills that matter too. Best to cultivate those as well as celestial navigation, as they go together.


I am more concerned about losing all the satnav constellations at once due to a common event -- RF noise, debris, hostilities among nations. If a lightning strike is your main fear you can wrap a cheap GPS and some spare batteries in tinfoil.
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Old 17-09-2018, 19:57   #8
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Re: Considering these ideas of navigation.. What is your opnion on it?

Quote:
Originally Posted by mikeod View Post
Sorry the accurate clock is easy you can get time signals with a cheap battery powered radio and set your Casio watch to that. I would not cross an ocean without celestial as backup.
A noon sight doesn't require anything more than approximate time and date, and is incredibly simple to calculate. There are even ways to manage without a sextant, I once got withing 30 miles of my real position with a plastic ruler used as a crude kamal. Also the Bris sextant is a brillant emergency navigation tool. But just an accurate DR and a list of lights will get you home.

https://en.m.wikipedia.org/wiki/Kamal_(navigation)

A backup handheld GPS wrapped in aluminium foil and stowed in a metal box is pretty simple insurance from a lightning perspective.

A copy of this is probably a better investment than a sextant.

https://www.bookdepository.com/Emerg...oaAt6oEALw_wcB

And the davis mk3 is a very effective tool, or better yet an old Ebco sextant.
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Old 17-09-2018, 21:02   #9
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Re: Considering these ideas of navigation.. What is your opnion on it?

Quote:
Originally Posted by fernandosmooth View Post
I always considered learning celestial navigation to use in case of a gps failure. The satellites not working or my units not working. Thinking of having at least 2 on board.


However I noticed that besides having a sextant, I also need a accurate clock, somehow

know my precise time then a nautical almanac. Probably other things I didnt consider yet.


So I am pondering here.




About the usefulness of it all and from my chair sitting on land I think it is not useful.


Lets see.. If I am in the middle of the atlanctic, crossing to the caribbean and all my gps stops working. I am probably well prepared on food, water.So I just continue going East. Then I just chill? I will hit America or somewhere else.



However if I am in South America with plans to go in Grenada and the gps fails. I just turn South. Then I just chill?


In the middle of the pacific, crossing from Chile to Tahiti or Australia. Gps stops working. I would be super well prepared considering it is a Pacific crossing and the doldrums and all that. So I go North? I would probably hit Japan or something. No way I would go right between the Bering Strait and into the north pole. Right? So just chill?




I would like your opnions on this, I will value it and reconsider my position (ha!), seriously because for now I am considering it is not worth. Thanks a lot.
what if all your water gets contaminated or your water storage tank ruptures and your water maker doesnt work because your batteries and motor are kaput or you couldn't afford one because your poor and you have 150 days worth of macaroni and cheese but only three days worth of water?

or what if you have a personal medical emergency or a terrible injury or a crew member does and you cant call for help and the epirb went over the side?

what if a giant school of killer sharks is chasing you and circling your boat like hungry, viscious animals and they want to eat you? this actually happened to two girls recently its a proven fact of packs of viscious wild sharks, tiger sharks circle boats trying to eat us...

these are all good reason why you might need to expedite your journey and find land like really pronto...
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Old 17-09-2018, 22:06   #10
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Re: Considering these ideas of navigation.. What is your opnion on it?

I'm an old navy trained navigator. Most digital watches keep much better time than the navy chronometers I used. Better ones keep perfect time. And there's always WWV for time. You need to practice and have your computations down pat or have good notes so you can get your fix in a timely manner. On a stable ship, the best I could do is get a fix within a mile. On a small boat, probably 5 miles. But it doesn't really matter unless you're around submerged reefs.

There are also European and Russian gps systems. I have all 3. You can buy a puck that reads them. Russia isn't world wide yet but works in the North Pacific.
As Jammer said: dead reckoning still works. I log Lat and Long at regular intervals so if it all goes down gps, computer, etc., I can roll out a chart and plot from there. If your depth sounder can read the bottom in deep water, you can also navigate by matching bottom features with depths, course and speed. I did that from the PI to Hawaii in constant cloud cover and a bad Loran set (before GPS). Also if you have a RDF, you can get bearings to radio stations. At night I sometimes got radio stations more than 1000 miles away. You can combine a sun shot and a radio bearing for a fix, too. And so on...
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Old 17-09-2018, 23:14   #11
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Re: Considering these ideas of navigation.. What is your opnion on it?

Hi,

Four of us recently discussed this topic on one of our sails. The argument quickly divided into celestial vs. faraday cage containing some well chosen devices (watches, GPS smart-phone/tablet with removable battery to avoid charging each month, sd card with world charts, battery pack, etc.).

No one in our group would think of crossing an ocean without some type of backup. For example, sailing east until you hit a landmass does not tell you when you will be in shipping lanes (and need extra vigilance). Plus you need your approximate location for weather/wind route planning.

In the end, I argued for both. Why the faraday cage? In an emergency, even if you learn celestial, the closest port may be small and you may lack even basic paper charts for that port. Plus, there may be times that you want the accuracy of GPS - 25 feet versus 5 miles with a mark 3 and the Kolbe book. Plus if you have means, there is no reason not to include an extra epirb, vhf and sat phone in the cage.

Why Celestial? This one is tougher. My best practical argument is that there are a few very low-probability situations where the satellites may not work, or your backups get damaged. Learning will take less than 75 hours, so why not use some of the free time on an ocean crossing to learn celestial. Someone countered, "Why not spend those 75 hours learning to troubleshoot a diesel?" Good point, but I'd try to do both. Remember, I did say this one is tougher.

My best argument is personal and may not apply to you. Finding my location to several miles using nothing but a 50 dollar plastic sextant, a 100 page book, a watch, paper and pencil is kind of cool. It reminds me that these principles were used a few thousand years ago to calculate the size of the earth. I like stuff like that, but I realize that others like other stuff.
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Old 17-09-2018, 23:27   #12
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Re: Considering these ideas of navigation.. What is your opnion on it?

Quote:
Originally Posted by Lepke View Post
I'm an old navy trained navigator. Most digital watches keep much better time than the navy chronometers I used. Better ones keep perfect time. And there's always WWV for time. You need to practice and have your computations down pat or have good notes so you can get your fix in a timely manner. On a stable ship, the best I could do is get a fix within a mile. On a small boat, probably 5 miles. But it doesn't really matter unless you're around submerged reefs.

There are also European and Russian gps systems. I have all 3. You can buy a puck that reads them. Russia isn't world wide yet but works in the North Pacific.
As Jammer said: dead reckoning still works. I log Lat and Long at regular intervals so if it all goes down gps, computer, etc., I can roll out a chart and plot from there. If your depth sounder can read the bottom in deep water, you can also navigate by matching bottom features with depths, course and speed. I did that from the PI to Hawaii in constant cloud cover and a bad Loran set (before GPS). Also if you have a RDF, you can get bearings to radio stations. At night I sometimes got radio stations more than 1000 miles away. You can combine a sun shot and a radio bearing for a fix, too. And so on...
The best position ANYBODY can get with a sextant is about 1nm, with good technique and averaging of multiple shots you might get a little better but the limiting is is the optical horizon can only be resolved to about 1 arc-min.

NIST is trying to zero out the funding for WWV &WWVH. Write your senators and representative and tell them this is a bad idea. The Navy just started teaching CelNav again because they are worried about GPS reliability and if they can’t get time updates that won’t work if they need it.

Even the timepieces the military has need to be checked against outside sources. Chip Scale Atomic Clocks are in the works but it’s not clear if they are available in significant quantities yet.
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Old 18-09-2018, 01:42   #13
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Re: Considering these ideas of navigation.. What is your opnion on it?

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Originally Posted by redbeard1 View Post
Hi,

Four of us recently discussed this topic on one of our sails. The argument quickly divided into celestial vs. faraday cage containing some well chosen devices (watches, GPS smart-phone/tablet with removable battery to avoid charging each month, sd card with world charts, battery pack, etc.).

No one in our group would think of crossing an ocean without some type of backup. For example, sailing east until you hit a landmass does not tell you when you will be in shipping lanes (and need extra vigilance). Plus you need your approximate location for weather/wind route planning.

In the end, I argued for both. Why the faraday cage? In an emergency, even if you learn celestial, the closest port may be small and you may lack even basic paper charts for that port. Plus, there may be times that you want the accuracy of GPS - 25 feet versus 5 miles with a mark 3 and the Kolbe book. Plus if you have means, there is no reason not to include an extra epirb, vhf and sat phone in the cage.

Why Celestial? This one is tougher. My best practical argument is that there are a few very low-probability situations where the satellites may not work, or your backups get damaged. Learning will take less than 75 hours, so why not use some of the free time on an ocean crossing to learn celestial. Someone countered, "Why not spend those 75 hours learning to troubleshoot a diesel?" Good point, but I'd try to do both. Remember, I did say this one is tougher.

My best argument is personal and may not apply to you. Finding my location to several miles using nothing but a 50 dollar plastic sextant, a 100 page book, a watch, paper and pencil is kind of cool. It reminds me that these principles were used a few thousand years ago to calculate the size of the earth. I like stuff like that, but I realize that others like other stuff.
Sounds like a great discussion and a good conclusion. A simple noon sight and the ability to take an amplitude to get a compass error is probably a worthwhile skillset for crossing oceans.
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Old 18-09-2018, 08:50   #14
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Re: Considering these ideas of navigation.. What is your opnion on it?

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NIST is trying to zero out the funding for WWV &WWVH. Write your senators and representative and tell them this is a bad idea. The Navy just started teaching CelNav again because they are worried about GPS reliability and if they can’t get time updates that won’t work if they need it.

Even the timepieces the military has need to be checked against outside sources. Chip Scale Atomic Clocks are in the works but it’s not clear if they are available in significant quantities yet.

I like WWV and remember using it as a reference station when I was experimenting with shortwave in my misspent yoof.


But there are so many practical alternatives. You can buy HAQ watches that are accurate within 10 seconds a year for a few hundred dollars with some careful shopping, or you can buy very inexpensive watches that are accurate within around 60 seconds a year but can be corrected by hand rating (so that you note that they gain or lose a certain number of seconds per month or whatever).


The CSACs are out there at $1500 each for just the module, but as far as I can tell can't be purchased as an assembled clock. Another science project.


You can also shoot lunars.
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Old 18-09-2018, 09:02   #15
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Re: Considering these ideas of navigation.. What is your opnion on it?

I'm in the camp that it makes MUCH more sense to have a backup GPS on your boat that the most fancy sextant and experienced user of such.

Face it, if GPS really were to go down you have much bigger problems to worry about than just not knowing exactly when you are on a boat.
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