Considering these ideas of navigation.. What is your opnion on it?

[Gypsyjon]

Originally Posted by mikeod

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.

Are you all aware that Trump is considering shutting down all our atomic clocks?


https://www.voanews.com/a/time-may-b...s/4554376.html

[mikeod]

Originally Posted by Gypsyjon

Are you all aware that Trump is considering shutting down all our atomic clocks?


https://www.voanews.com/a/time-may-b...s/4554376.html

I know, hopefully they will just fire all the useless dead weight and automate the time signal. 26 million to send out a time signal seems excessive.

[stewie]

You can use a portable radio as an RDF. For example find a medium wave radio station on say Barbados. Turn the radio to the null ( most inaudible) position and that is the direction of the radio station. I did that a long time ago after my satnave was taken out by a storm and we were left with a Davis sextant, which my skills were only good enough to give me a position of about 30 miles from where I was. On the chart it looked like we had zig zagged across the Atlantic, but we got there just the same. DR can also be be good enough to get you where you want to go.

[MJH]

Originally Posted by fernandosmooth

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.

First some corrections, if crossing to the Caribbean you just continue WEST not east; secondly, if going to Grenada from South America you go NORTH not south.

I am a retired USAF navigator and made hundreds if not thousands of celestial shots...many times that is all we had because other equipment was not working properly. But all of that was above 18,000' and most above 31,000' where visibility was almost always good. On my recent voyage to Hawaii one of the surprises were the overcast conditions, particularly in the North Pacific where we went for eight days in overcast conditions...not good for celestial. Furthermore, I asked a fellow crewmember (retired Navy navigator) if I should bring a sextant for entertainment and he said "No", and I didn't.

Years before when I sailed solo across the Gulf of Mexico (Key West to Galveston) I carried a sextant, almanac, and H.O. 249 volumes as well as two GPS's. When the complete power failure happened I continued to Texas with the old Garmin 45 GPS, the large stack of batteries I brought along, and Monitor windvane which does not require electrical power. I never used the sextant and returned it to West Marine to get my money back, I only recently sold the reduction tables. I had planned to refresh myself on the journey but never got to it...if you are going to use celestial, learn before you depart.

While the theory is the same the procedures and sextants used are very different for aerial and marine celestial navigation, the latter I never really learned as I said previously. In my career we were normally traveling at 400 - 500K and any heading error quickly turned into many miles off course so fixes were required every hour...not so for sailing at 6K.

That said, celestial is very interesting and should be pursued if you are interested. Presently the competitors in the Global Globe Race - 2018 (GGR-2018 which began July 1, 2018) are sailing around the world without modern navigational equipment, obviously using celestial. Tami Oldham Ashcroft used celestial in saving her life albeit using a timepiece 24 ours off (movie "Adrift" based on her much better book Red Sky in Mourning). Steve Callahan used the fundamentals of celestial during his 76 days lost at sea in his book Adrift. You can't have too many spare parts, too much drinking water, or too much knowledge sailing offshore.

Lastly, when bad things happen its usually not just one thing that goes wrong but multiples which previous posts have alluded to. Best to think of that in preparing yourself.

"If anything is going to happen, it’s going to happen out there." --Captain Ron (1992)

Good Luck.

~ ~ _/) ~ ~ MJH

[grantmc]

Originally Posted by er9

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

It's not really that the sharks are trying to eat the crew. The animals have learnt that hanging around boats you'll get a free feed. And it's their favourite; fish. Plenty of boats throw fish to them, just ask any seagull where they get dinner most of the time. It's a learned behaviour, but the animals can't distinguish between fishing boats and others.

Originally Posted by Gypsyjon

Are you all aware that Trump is considering shutting down all our atomic clocks?

If Trump finds out that all of us non US people use the US GPS network for free I can foresee problems, similarly if there is a serious war. The US would turn off their GPS network in a heartbeat if an enemy had the potential to use it for GPS guided attack.

Clinton made GPS available with near military accuracy to the world at the end of his presidency. Up till then GPS for much of the world was often no better than celestial.

I’ve always been grateful to the US tax payers who give me GPS for free. But I’m also aware that they might choose to take it away. So I’m certainly in the celestial camp. It took some effort to learn sure, but it was mostly fun. I have a couple of cheap plastic sextants and as Snow Petrol said a midday sun sight is enough for most needs.

[Nicholson58]

Buy any number of hand held GPS navy computers you like. Make sure they all use the same Navionic chip. Store them away in metal boxes without the batteries installed. These are your backups. In addition, we have four active GPS units including laptops and tablets.

In two years of the Caribbean we have only seen lightening flashes twice and not violent. Great Lakes, Midwest, many times. We have total positive and negative wiring double pole rocker switches to totally isolate each individual electronic device onboard. Antennas are either manual or switched to disconnect. None of my isolated devices has ever been compromised through three strikes on Lake Michigan. One direct strike blew 18fuses and fused wiring in the bow. Several LED lights were destroyed along with the mounted antennas and the Windex.

[Gypsyjon]

Originally Posted by grantmc

It's not really that the sharks are trying to eat the crew. The animals have learnt that hanging around boats you'll get a free feed. And it's their favourite; fish. Plenty of boats throw fish to them, just ask any seagull where they get dinner most of the time. It's a learned behaviour, but the animals can't distinguish between fishing boats and others.




If Trump finds out that all of us non US people use the US GPS network for free I can foresee problems, similarly if there is a serious war. The US would turn off their GPS network in a heartbeat if an enemy had the potential to use it for GPS guided attack.

Clinton made GPS available with near military accuracy to the world at the end of his presidency. Up till then GPS for much of the world was often no better than celestial.

I’ve always been grateful to the US tax payers who give me GPS for free. But I’m also aware that they might choose to take it away. So I’m certainly in the celestial camp. It took some effort to learn sure, but it was mostly fun. I have a couple of cheap plastic sextants and as Snow Petrol said a midday sun sight is enough for most needs.

That's a riot, thanks for giving me a good laugh this afternoon!! Hope all is well on the other side of the world.

From time to time the guys at Tyndall Airforce base here in North Florida mess with GPS. While I was on the Great Loop in May, they turned the time back 4 hours, with no notice etc. I called the Coast Guard and they said they had no warning, but suspected that Tyndall was doing some experimenting. They have a bunch of towers off shore in the Gulf of Mexico that they do navigational experiments using the tower and GPS...I would love to know what it is they are doing, but of course its top secrethttp://www.cruisersforum.com/images/smilies/whistling.gif

[TarponChaser]

Has anyone actually seen a handheld GPS “fried” in a lightning situation? (truely air gap, not connected to charger) If so, was unit powered up? And likewise has anyone seen a powered down handheld damaged.

If handheld and powered up, did person holding it survive?

[Adelie]

Originally Posted by mikeod

I know, hopefully they will just fire all the useless dead weight and automate the time signal. 26 million to send out a time signal seems excessive.

It's not $26M, it's $6.3M. There's not a lot of dead weight for this function, the money goes to maintain and operate 2 radio stations that broadcast on multiple frequencies with enough power to be received several thousand miles away. The process is pretty much automated already.
NIST doesn't want to continue the service, it's dull. They want to do cutting edge stuff. The problem is that the military needs the service if they ever need to fall back on Celestial Navigation. They are concerned enough about this to have reintroduced CelNav at the US Naval Academy after discontinuing instruction for the previous 9yr. If there are no time signals, then military use of CelNav will be compromised.

Originally Posted by grantmc

....
Clinton made GPS available with near military accuracy to the world at the end of his presidency. Up till then GPS for much of the world was often no better than celestial.
....

Not so. The reduced accuracy positioning available to the general public was referred to as Selective Availability (SA) and resulted in positions errors in the range of 25-100m. The best accuracy that can be counted on for CelNav is on the order of 1nm with 2-5nm being more common. GPS with SA on was still at least 20x more accurate than CelNav.

[boatman61]

In this day and age cellestial should/is not needed for the 'Milk Run' routes across most oceans..
DR coupled with Pilot Charts and a decent chart covering say 50nm either side of your destination.. a hh compass and last known position before system failure.
Thats if one is Geografically aware.. a fading skill with gps for everything and navigation going tech.. hell one can switch on, enter a destination and a series of WPs avoiding obstacles pops up..
Who needs Aware..???

[NevisDog]

If cruising is all about self-sufficiency and being independent of any outside assistance, then DR and Celestial are front and centre of cruising. Only this latest generation of cruisers would even ask the question. Reducing a sun sight and having a LOP within a mile or so of the GPS is the most fun you can have in a boat while vertical - it can't be beat.

Buy a top-quality German or Japanese or Chinese sextant, a used one is fine, can be bought from the ship-breakers yards in India for a pittance and having such a wonderfully crafted piece of scientific equipment aboard increases the fun. Any digital watch is far more accurate than an expensive chronometer used to be - just check how much it gains each day over a month or so and it's good to go. Almanacs can be downloaded for free. Sight reduction tables can be replaced by a good scientific calculator (or two) costing just a few dollars and that allows us to use the GPS location as our assumed position, giving me an instant high whenever the intercept is less than 1 mile (which it so often is in good weather, just by the law of averages).

Paper charts, DR and celestial are, for some, the very definition of cruising - hell what's the point of sailing if some darned computer is helping us every step of the way? We're not cripples yet, are we? Even today, you cannot qualify as a yachtmaster without mastering this stuff. Who needs diesel repair skills - that's what sails are for.

[DEAN2140]

In 1989 I sailed with the precursor of GPS called SatNav, which gave you a position 2 or 3 times a day. It went down while sailing from Tahiti to Hawaii. If I missed Hawaii, I would have landed in the Aleutians but I had a Davis plastic sextent, a ham radio and digital watch for time, and a calculator with a celestial program. We arrived in Hawaii with no drama but using celestial transformed my experience on the water. We took three sun sights per day........made me feel like a "real sailor". IMO, sailing without this back up would be very foolish.

[captmikem]

I think your time will be better spent honing your DR skills.
Celestial Navigation is not something you become accurate with in a few days nor can you whip out your sextant and grab a position anytime you want.
Remember a sight gives you a LINE of Position. You then need to cross it with another LOP to get a fix.

You can DR anytime and any weather.
I hav DR'd most of the way across the atlantic when I could not see anything for days.

Learning celestial navigation is a handy and valuable skill but do not expect to learn it and be accurate with it without considerable time spent practicing.

M

[Paul Elliott]

I figure that if I lose my GPS and clocks, I can still do noon sights (with sextant, a calendar, and the Almanac) and run down the latitude until I see land. Not that I expect to need to do this...

[captmikem]

Up till then GPS for much of the world was often no better than celestial.

[/QUOTE]


I do not think you have a good grasp of celestial navigation.

GPS degraded signal, "selective availability" as it was called gave an instant fix that was typically accurate to within 100 meters, Every second of every hour of every day.

Near Shore DGPS corrected the signal to within a meter.

At dawn and dusk on a clear day/night, 30 minutes to an hour spent shooting and working out star sights will give a good navigator ONE fix. Possibly accurate to within a quarter mile (maybe an 8th mile on a calm night).

M