Celestial Navigation

[btrayfors]

Originally Posted by rockDAWG

Not try to change the topic here.

If you need to ditch you SV and climb up to the life raft. Beside the other essentials, what would you rather take, GPS with spare battery or your sextant charts, calculator and etc.

Let here from the both sides.

Neither. I'd clutch my EPIRB with a death-grip :-) With or without GPS (the built-in 121.5mhz beacon will pinpoint you when help arrives).

Without this and with a fully functioning portable GPS, at least you'll know your own position with certainty when you die of thirst or starvation!

Bill

[ffiill]

Mid day sun sights are easy-then all you do is use a sight reduction table and proformat sheet into which you put the numbers and do some simple adding and subtracting.
Of course the most fun is dead reckoning plus a sighting line and stick-the Polynesians got to NZ that way and across the south Pacific.One you have got the angle marked up the next person who wants to find you just sails either north or south until they get the same angle ;placing them on the same longtitude;then east or west to reach you.
I have a couple of GPs s as well and the astro calculator from Pangolin

[AdamLein]

Originally Posted by rockDAWG

If you need to ditch you SV and climb up to the life raft. Beside the other essentials, what would you rather take, GPS with spare battery or your sextant charts, calculator and etc.

I'm assuming this thought experiment is taking place far enough from land and popular routes that you expect to be drifting for a while.

You don't need charts to use a sextant. You need to know the sun's declination, which you can compute on your calculator of choice. But that's besides the point; would you really consider not taking charts with you when you abandon your vessel? At the very least you should have pilot charts so you can keep track of the currents.

Personally my handheld is usually in a jacket pocket if I'm not using at the moment, so if I'm grabbing navigation devices, it comes along for free.

[jackdale]

Originally Posted by AdamLein

Personally my handheld is usually in a jacket pocket if I'm not using at the moment, so if I'm grabbing navigation devices, it comes along for free.

My ACR Aqualink PLB is with me at all times offshore.

The grab bag contents vary; long passage versus 50-100 miles offshore. But a GPS is a waterproof bag is one requirement along with a VHF in a waterproof bag.

[cb32863]

It still befuddles me the "anti" attitude towards learning celestial nav. Both here and on AS. I find it intersting to learn and folks were getting around just fine for a few hundred years, if not more, with it. As the only way to nav thses days, no, of course not but, why not learn it if you want to. If you see no need then don't and you really shouldn't discourage others from doing so.

My 2 cents.

[Omatako]

Originally Posted by btrayfors

Neither. I'd clutch my EPIRB with a death-grip :-) With or without GPS (the built-in 121.5mhz beacon will pinpoint you when help arrives).

Without this and with a fully functioning portable GPS, at least you'll know your own position with certainty when you die of thirst or starvation!

Bill

No question about the EPIRB if you have one. But the GPS in concert with the portable VHF that we all carry in our grab bags allows the searching vessel pottering around on the horizon to find you much easier.

Originally Posted by AdamLein

You don't need charts to use a sextant. You need to know the sun's declination, which you can compute on your calculator of choice. But that's besides the point;

Agreed. Following on from Bill's thoughts above, with celestial gear in the life-raft you will have only a vague idea of where you are when you die of thirst and starvation.

Originally Posted by AdamLein

which might be a good idea, so that you aren't all rusty at finding call boxes once The Man or The Sun or Zeus or whoever comes and shuts down your satellite phone. Assuming you're concerned about that.

Maybe it's different where you live but where I live finding a call box would be serious challenge, almost an impossibility.

Originally Posted by cb32863

It still befuddles me the "anti" attitude towards learning celestial nav.

Actually I thought the majority of posts here were positive towards learning and using celestial nav. The pure reality though is that the vast majority of recreational/cruising sailors today use it for recreation if at all. Bottom line is I can buy several GPS units for the cost of a good sextant and whilst it is true that a GPS can let you down, stumbling on a heaving deck and dropping/banging a sextant and rendering it useless is also not beyond the realm of possibility. In addition, sight reduction tables are expensive as are nautical almanacs which should be replaced annually. Most cruising sailors these days would rather avoid this expense. And in any case for coastal navigation, the sextant and its associated paraphanalia is academic.

Originally Posted by cb32863

Of course the most fun is dead reckoning plus a sighting line and stick-the Polynesians got to NZ that way and across the south Pacific.

Much like the pioneers crossed America in tented wagons . . . . but they don't anymore.

Excuse me, I'm just having fun, I don't pooh-pooh the use of celestial nav, I think it's a lot of fun and we often take sights and plot position lines and fixes when we're at sea. But the really fun part is checking the GPS to see how close we got.

[Slayer]

When I was in Hawaii I read that the Polynesians would lay in their boats and feel the waves to estimate their location. I think they did it in conjunction with celesitial navigation, but it still is pretty amazing.

[genieskip]

One point that needs to be made is that if all the electronics on the boat go belly up your sextant might not be much help because the third requirement for celestial navigation (after a sextant and sight reduction tables or a nav calculator) is accurate time. Very few, if any, cruising sailors have a calibrated chronometer, one which has been monitored carefully so that the error is known and can be corrected for, to fall back on.

Almost all celestial navigators I have sailed with, myself included, use a radio time tick to set a stopwatch to get an accurate time on their sights. No radio = no accurate time = one line of position each day at noon of your Latitude - if a cloud doesn't obscure sun at just the right moment. Better than nothing, but far from ideal. If you get hit by lighting, as happened to me on a Bermuda-Halifax many years ago, and all the electronics get fried you are in deep doodoo. We had a good recent fix and weren't that far from land so we were able to stumble our way in by Dead Reckoning but it wasn't easy and I was glad we had a really good navigator aboard.

So you need to keep in mind - if you want to have a sextant aboard by all means do so and learn to use it, but remember it isn't much help without accurate time.

[btrayfors]

Genieskip,

Very good point.

However, as you point out, you can get an LOP for your latitude each day even without accurate time.

Moreover, most everyone has a good quartz watch these days. If you are reasonably prudent, this can serve very well. Don't forget, an error of 4 seconds = 1 nautical mile, so even an error of a minute or so only results in an error of 15 nautical miles. In many instances, that would be sufficient.

It would also afford a good opportunity to "run down your latitude".

BTW, I give a "time tick" on the WaterWay Net (7268 kHz LSB daily @ 0745 Eastern time) whenever I'm net control, just in case anyone really cares about time accuracy :-)

Bill
WA6CCA

[rockDAWG]

Without an apparent answer, I come to the conclusion that if you can only to either GPS or Sextant, all would take a GPS. However, I am sure there a few whose balls are all hair will take the sextant. All power to you.