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

[NevisDog]

Originally Posted by longjonsilver

OK, call me a luddite if you will, but i would like to find printable trig tables to the minute of accuracy. ...

Norie's Tables - all your sines and cosines but also hundreds of pages of log-sines, log-cosines, log-haversines (from memory) and exactly how to use them for navigation. I still have the book somewhere but haven't used it since the advent of scientific calculators (programmable ones even better).

[Snowpetrel]

Originally Posted by NevisDog

Norie's Tables - all your sines and cosines but also hundreds of pages of log-sines, log-cosines, log-haversines (from memory) and exactly how to use them for navigation. I still have the book somewhere but haven't used it since the advent of scientific calculators (programmable ones even better).

It's gotten smaller over the years. My grandfathers newer copy. And my great great uncles old copy, used when he was mate on Square riggers.

I am not going to take the old one to sea. Bit of a family treasure.

[longjonsilver]

Originally Posted by Adelie

Both the Nautical Almanac and Kolbe's long term almanac have the Concise /NAO sight reduction tables.

Good to know. i ordered Kolbe's long term almanac. i guess that will do it?

[NevisDog]

Originally Posted by Snowpetrel

It's gotten smaller over the years. ...

Looks like I got the concise version.

[belizesailor]

Originally Posted by GrowleyMonster

Oops clicked wrong button.


Well, you can derive approximate time from LAN if you know your Longitude, yes. If you are not sure of your Longitude, then LAN observation will still leave you guessing what time it is. You need something to nail down either Longitude, from which you can easily derive time, or time, from which you can derive Longitude. One or the other. Unless you resort to more esoteric methods like Lunar Distance or other such astronomical/mathematical hocus pocus. Assumed Position or DR Position or Estimated Position is not going to cut it. Using such methods as a time check will put your DR and your non LAN LOPs off even more, and when you then use that erroneous Longitude to determine time by LAN the next day, you are off even more.

I did not intend to imply you could derive accurate time from LAN...thats why I said "approximate"...certainly not accurate enough to use for celestial nav purposes.

[edexter]

That's why I joined the US Power Squadron, to take courses and learn what I was doing. They offer an extensive course in celestial navigation, but I would take Piloting, Advanced Piloting, and Junior Navigation first. (For puttering around the northern Chesapeake in a 22-foot Rhodes 22 like we do, Piloting was invaluable, but if I was doing any blue-water I would definitely take the others). Hah, our primary navigational system, the I-pad, has gone out plenty of times, and I had to resort to the handheld GPS; if that went out, I would start to get nervous, if I didn't already know where I was. Our chapter in Baltimore joined with Annapolis to give a weekend refresher in celestial navigation over in Rock Hall the last couple of years, if you think you know what you are doing already something like that could be very helpful.

[ninethlife]

Northern hemisphere...Shoot the North Star...plus or minus 1 degree...there's your latitude.

[davefrediam]

Hi all
I also wanted to get a grasp of celestial navigation so I bought some books on the subject and used the teacup link, all cheap free and easily available.
On the sextant front I bought an old (but in great working condition) sextant off ebay at around £100 not so cheap.
On the time front I researched online what are the most accurate watches, and surprisingly its definitely not your super expensive Rolex etc. I found it was citizen and a branch of Citizen called Bulova, so I purchased one these (a titanium 100m waterproof model) for around £150, once again not so cheap but certainly not Rolex prices.
However the biggest stumbling block I found was obtaining celestial almanac tables. I was hoping I could find some free online source for this basic information but after many hours research I was getting no where. Yeah I could go down a chandlery and buy some for around £40 but these would only cover upto a year!
Yet there was loads of free Apps available for my android phone that you put the basic data into (covering all major celestial objects) and give you your position, which cover you for years ahead and must have the table information programmed in!
If anyone knows of a cheap resource for celestial tables I would be most interested!

[home_maarten]

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.

Uh... Going East in the middle of the Atlantic???? Think you'd be back in Europe/N. Africa sooner ... Maybe first buy a globe ?

[camaraderie]

I didn't have time to real all 6 pages...and I'm sure most of the arguments pro and con have been beaten to death. I'm on the not needed side of the equation but would not discourage anyone from learning celestial...or wagon wheel repair if it is of interest.

We had 2 active GPS units while underway...and TWO handheld battery operated GPS units stored with a bag of AA batts in our microwave which serves as a Faraday cage. We could confidently sail without worrying about lightning strikes or electrical failures since checking course and heading on a handheld GPS takes only a minute and we had weeks worth of batteries available.
The only thing we could not compensate for was a complete satellite system failure, in which case the advice is to look to avoid the mushroom clouds and head the boat south.

[LifePart2]

One day on my first Atlantic crossing I was practising with my Plastimo sextant when bounce, bounce, bounce, plop... the eyepiece from my sextant fell off and bounced into the drink.

Thank goodness I could go to my backup nav system (my GPS) so that I could complete our crossing!

[Cadence]

Originally Posted by home_maarten

Uh... Going East in the middle of the Atlantic???? Think you'd be back in Europe/N. Africa sooner ... Maybe first buy a globe ?

He can buy a globe and just chill. I believe all of his posts have been in jest? I hope.

[Atalantia]

Originally Posted by 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?

We have a lot of violent weathering here in Cambodia. Lighting strokes sometimes just meters away from our house, and the whole building is jittering. I have 6 iOS Devices here and they are always on. The lighting never destroy'd any of them although I buy about two routers per year.

[GrowleyMonster]

Originally Posted by ninethlife

Northern hemisphere...Shoot the North Star...plus or minus 1 degree...there's your latitude.

Properly corrected, Latitude by Polaris can be MUCH more accurate than that. Same accuracy as you can expect from LAN or any LOP. Enter the Polaris tables in the almanac with LHA Aries for the correction, and the rest is normal correction for dip, refraction, etc. Error in calculation will be less than your sight error on a small boat, in most cases.


For rough and ready lifeboat navigation, just remember that relative to the celestial north pole, polaris is opposite from cassiopeia at a distance of 40' from the pole. Estimate the angular position of Polaris in its tiny circular path around the North Pole, and use basic trig to find the corrected height. That will put you surprisingly close on your Latitude, without tables and without accurate timekeeping or in fact any timekeeping at all. You're welcome.

[longjonsilver]

Originally Posted by davefrediam

On the sextant front I bought an old (but in great working condition) sextant off ebay at around £100 not so cheap.

i spent $20C on a Davis sextant and $150C on a professional grade Freiberger Trommel-sextant after negociating with the guy for a month!

Originally Posted by davefrediam

On the time front I researched online what are the most accurate watches, and surprisingly its definitely not your super expensive Rolex etc. I found it was citizen and a branch of Citizen called Bulova, so I purchased one these (a titanium 100m waterproof model) for around £150, once again not so cheap but certainly not Rolex prices.

You're ahead of me on that one, thanks for the research.

Originally Posted by davefrediam

However the biggest stumbling block I found was obtaining celestial almanac tables. I could go down a chandlery and buy some for around £40 but these would only cover upto a year!

i bot this book off Amazon for $20C - it should last the rest of my life.
Long Term Almanac 2000-2050: For the Sun and Selected Stars with Concise Sight Reduction Tables, 2nd Edition by Geoffery Kolbe

Originally Posted by GrowleyMonster

For rough and ready lifeboat navigation, just remember that relative to the celestial north pole, polaris is opposite from cassiopeia at a distance of 40' from the pole.

Huh??? i'm lost. Can you explain?
jon