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

[captainwoody]

With your ‘just chill’ attitude, you are way ahead of the doomsday commenters here.
I circumnavigated with a handheld gps. I had (and suggest) a cheap sextant and the necessary tables and the ‘how to do a noonsite’ guide onboard. I had done some practice sites before but you’ll need a refresher. It’s a one in a million chance you are going to lose all electronics in a mid ocean lightning strike. If all devices miraculously disabled, you’ll have plenty of time to play with the cool sextant gear/tables/tutorial.
For our ocean deliveries now, all of our devices have gps and glonass etc. and we use chart apps on all of them. We don’t bring tables and sextant on deliveries.
Yes, heading toward where you think land is, is a viable plan. Hoving-to at night if conerned about hitting reefs etc. would be part of the plan.
Other options:
-dead reckoning. You should be writing your gps position and speed, compass, baro, wind; in a log after every watch at least (every 3 hours on my boats). It’s easy and you can recreate your dead reconning progress in your new found spare time.
-radio directional finder will lead you to any land that transmits anything.
-ship traffic. Head for shipping lanes as they can give you location and weather info or let authorities know if you feel your predicament warrants.
Have an amazing Adventure!

[GrowleyMonster]

Originally Posted by longjonsilver

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

Look at the northern sky assuming you are in the North Hemisphere. Look at the celestial north pole. You can't see it but you know it is there. You can see Polaris, though. It is located NEAR the celestial North Pole, 40 minutes of arc away from it. Locate Cassieopeia. The star in that constellation nearest to Polaris is almost directly opposite from Polaris. The actual celestial North Pole is between them, near Polaris but 40' distant. Think of the visible sky in that vicinity as a plane, for a moment. It is vertical, and facing you. Let's say Cassiopeia is to the left of Polaris, and a line between them is dead horizontal. North is 40' to the left of Polaris. It is the same height as Polaris. No correction needed.


Let's say that Cassiopeia is directly above Polaris. Polaris then, is 40' lower than the celestial North Pole. So, a correction is needed to be added to HS to get the height of the celestial North Pole above the horizon. 90 degrees minus this corrected Sextant Height (HS) gives you Latitude. With an accuracy of a minute or less. In other words, within one mile North or South. But if Cassiopeia is above and to the left of Polaris, then you have to trigonometrically find the height difference between the celestial North Pole and Polaris assuming a hypotenuse of 40 and an angle that you visually approximate. Let's say it is 45 degrees. The vertex of the angle is the unseen Celestial North Pole. The end of the hypotenuse is Polaris and the length of the hypotenuse is 40. You need to solve for length of the Opposite leg of the triangle. Sine = Opposite divided by Hypotenuse. So Opposite = Sin(45) * 40 = 28.28 and since you know Polaris is below and to the right, you add this to the HS of Polaris, then subtract the result from 90 for Latitude. If trig confuses you, just draw a circle with a radius of 5". Now draw Polaris on the edge of the circle, and the northernmost star in the constellation Cassiopeia directly opposite on the circle. Draw a line between them passing through the center of the circle. No its not to scale but it doesn't have to be because the polar distance of Cassiopeia is irrelevant. Draw a horizontal line through the center, i.e. running directly Right to Left from one side of the circle to the other. How high is the mark for Polaris, relative to the horizontal line? Measure it off and multiply by 8 because we have scaled the radius and therefore the hypotenuse to only 5" so 1/8" = one minute. In this case it is a bit over 3.5" so call it 28 minutes correction. So, you can do it graphically or you can do it mathematically, but a good approximation of the HS of the North Pole can be derived from the HS of Polaris and the relative position of Cassiopeia.


Are you unsure what is meant by Celestial North Pole?


Think of the sky all around the Earth as the inside of a sphere having infinite radius with Earth at the center. Project the North and South poles onto the inner face of this celestial sphere. That is the Celestial North and South Poles. Hour Angle meridians are analogous to Longitude lines on the Earth. Just as Longitude is arbitrarily relative to Greenwich, Celestial "Longitude" is based on Aries, which is where we get the term LHA, or Local Hour Angle of Aries. Declination is analogous to Latitude. There is a celestial Equator. Parallels and Meridians, just like on Earth, exist at least conceptually on this Celestial Sphere. And that is the basis of celestial Navigation. Every point, every pair of coordinates, on the Earth's surface has a corresponding point on this imaginary but very useful sphere.

[captainwoody]

And you won’t need a chronometer to figure your latitude. If you have a chart you should be able to target island groups with dead reckoning.

[barnakiel]

Casio USD 15 watch.


OR


A mechanical chronometer ($$$).


Both have their merits.



I only own the former device.


b.

[Cadence]

Originally Posted by barnakiel

Casio USD 15 watch.


OR


A mechanical chronometer ($$$).


Both have their merits.



I only own the former device.


b.

A cheap Casio, no moving parts.

[wingssail]

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.

Learning Celestial is a great idea, not because you need to know it for a navigation emergency, but just as a skill to learn and to re-forge your connections with sailors past.

But for navigation back-up it isn't the most practical solution. Aside from being exceptionally unlikely that you'll need it, learning to do it (as explained in several posts), keeping your skills up to date, and keeping your timing device on-time, will require a certain amount of on-going attention. Keeping that attention span for years, when you never need it, is a big investment of time and energy, which could be spent on other activities and skills, perhaps more useful.

As far as navigation backup we each should have a Plan B, and Plan C, neither of which require celestial. Plan A, of course, is your normal GPS based, electronic charts.

Plan B. If your GPS is down , your power down, or GPS itself is down, or you are hit by lightning, you should be carrying several GPS receivers including ones which pick up other satellite constellations. Keep one or two, with batteries, in either a Faraday cage or the oven. (Also keep a hand held VHF and a laptop with charts). If you are hit by lightning, or a nearby surface strike, and your electronics are fried, maybe this approach will protect your critical devices.

Plan C. If all power is out, and all GPS systems offline, if you keep paper charts of the ocean area you plan to sail in and have guide books for the harbors where you might make a landing, you can get close to a destination using the paper chart, which will have islands and reefs on it, (unlike some vector based electronic charts), and finally navigate into harbor using the guidebook, no power, no systems.

For this you will need some dead reckoning skills. They are less technical than celestial and if you've kept a position plot on your ocean chart, picking up a dead reckoning plot isn't too hard. A magnetic compass and a chip of wood on a string will give you heading and speed. Pilot charts and books will give you some indication of current and dangers.

But all of this is not really the best way to spend your time. You really don't need to put much effort into covering the situation where all power is lost and all GPS systems have fallen out of the sky. Other comments have used sarcasm to point out the unlikeness of this eventuality. We started using GPS in 1993. It has never failed. We carry spares. We've never needed them. We put some devices in the oven when we are in lightning storms, we've never been hit. We've used electronic charts since 1998 and discontinued carrying a catalog of paper charts since 2002. We now carry one large ocean chart and guidebooks. For navigation we use a laptop computer and electronic charts, with a spare, plug and play, laptop and plenty of chart back-ups. We've gone to the spare once or twice.

Let's look, however, at other scary scenarios which you could plan for:

What if your engine is down and you need to get off of a lee shore? (How about in 25 knots?) Doing this requires skill and practice and you are likely to need it someday.

How about coming into an anchorage or marina berth under sail?

How about how to diagnose and fix a charging system failure, and what spares should you have for that?

Same with autopilot.

How about dealing with torn sails? Can you sew them? What do you need? Or, heaven forbid, broken spars or rudder. While sitting on that couch you could think through these things, and get prepared.

General mechanical, electrical, and electronics repair ability are critical skills which you definitely will need long before GPS ceases to exist. Get these skills and use them.

The list goes on. Let's try to focus on the likely eventualities.

[David M]

Back in the old days, three mechanical chronometers were kept on the bridge. Before getting underway, the daily gain or loss of each clock was recorded. When needing to do their first celestial fix, there they had it, a pretty accurate estimate of the time.(longitude) The three clocks created some redundancy in case one of the clock's rate of change, changed, became highly inaccurate or failed altogether.

These days I would just have three cheap Casio electronic watches and record their daily gain or loss from WWV...in case that goes out or GPS goes out or both. This is highly unlikely but if you want to be a purist about this and fully independent. This would keep you independent of land based signals and give you enough time to reach your destination safely and relatively accurately.

Keep some paper sight reduction tables, a Nautical Almanac and some plotting sheets.

BTW, to correct a little inaccuracy from an earlier post, your correction of Polaris, declination, will depend on the time of night and the date. Being wrong could have your latitude incorrect by as much as 100 Nm sometimes. Remember that Polaris rotates around true North at 89 degrees 16 minutes.

[David M]

Correction: I got timed out.

BTW, to correct a little inaccuracy from an earlier post, your correction of Polaris, declination, will depend on the time of night and the date. Being wrong could have your latitude incorrect by as much as 88 Nm sometimes. Remember that Polaris rotates around true North at 89 degrees, 16 minutes. 90 minus 44 degrees times 2 is 88 minutes. 88 degrees is 88 Nm of latitude plus whatever error you get with height of eye.

[Adelie]

Originally Posted by David M

Correction: I got timed out.

BTW, to correct a little inaccuracy from an earlier post, your correction of Polaris, declination, will depend on the time of night and the date. Being wrong could have your latitude incorrect by as much as 88 Nm sometimes. Remember that Polaris rotates around true North at 89 degrees, 16 minutes. 90 minus 44 degrees times 2 is 88 minutes. 88 degrees is 88 Nm of latitude plus whatever error you get with height of eye.

Incorrect, the range of error is 88 arc-min,but the max error is half of that which is 44’ which is equal to 44nm.

[fernandosmooth]

If you lose your mast in the middle of the atlantic, you better just chill and let the current take you to the caribbean. I should have said West, not East but english is not my first language and sometimes I mix those up. Not because I dont know where they are. On going to the caribbean from south america, I meant south because I would rather turn back than to look for small islands if gps breaks.



So yes. I would most likely not try to hit Papeete on the middle of the Pacific, trying to get my celestian navigation right, a skill that most likely wont be that precise if I need it, I would rather go north to hit somewhere in Asia, Australia or America.


I think it is better to turn back and have another drink. I would only try it if there was no other way but if I am well prepared on food, water and things then I would most likely just chill really.

[longjonsilver]

Originally Posted by fernandosmooth

but english is not my first language and sometimes I mix those up. Not because I dont know where they are. On going to the caribbean from south america, I meant south because I would rather turn back than to look for small islands if gps breaks.

Are you from Brazil? i would love to visit there in my sailboat. Florianopolis looks really fun.
jon

[GrowleyMonster]

GAAAAAAAAKKKKKKKK! Brain fart alert!!!! You don't subract HS of the North Pole (corrected height of Polaris) from 90 to get Latitude. It IS latitude. You don't subtract from 90. Sorry if I confused anyone!

[fernandosmooth]

Originally Posted by longjonsilver

Are you from Brazil? i would love to visit there in my sailboat. Florianopolis looks really fun.
jon

Come! I am right in the north, where the amazon river meets the Atlantic, I will help you out with language and things.

[fernandosmooth]

Originally Posted by captainwoody

With your ‘just chill’ attitude, you are way ahead of the doomsday commenters here.
I circumnavigated with a handheld gps. I had (and suggest) a cheap sextant and the necessary tables and the ‘how to do a noonsite’ guide onboard.




....

Originally Posted by wingssail

Learning Celestial is a great idea, not because you need to know it for a navigation emergency, but just as a skill to learn and to re-forge your connections with sailors past.

But for navigation back-up it isn't the most practical solution.



....

I would like to thank both of you wingsail & captainwoody for saying things I agree with! I also thank everyone even with contrary ideas. I have a lot to think about. Keep adding stuff. It is hard to thank everyone but your input on this is very nice. I appreciate it.

[fernandosmooth]

Growley, do you get crawfish yourself there in nola or do you buy it?


edit: I dont know if offtopic conversations are allowed.