Sextant fanatic

[30boat]

A friend of mine called me a sextant fanatic because I said that I wouldn't put to sea without one.GPS is here ,says he, and all you need is a spare portable set with plenty of batteries.
Although that makes sense I will still take my sextant with me and also two GPS sets.I'll sleep better knowing I have a backup that doesn't need batteries or fancy satelites.
Am I beeing overly cautious?


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[Neal]

Yes, but....

the sextant is much more: cuddly, fun and interesting than the gps anyway, so no harm in having it aboard.

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[Talbot]

presumably you have several extra quartz watches for accurate timing for your fixes, or are you using the time from the GPS sets - in which case why not just use the GPS!!!!

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[stephenh]

Re: Don\'t....

Whatever you do, don't use the GPS for astro.

The GPS keeps "GPS time" and this varies considerably from GMT, UTC, Zulu time or whatever....

I think it was Tom Cunliffe that said something along the lines of "a good astro fix gives you the feeling of being at one with the universe and this is something you cannot get from a black box "

I agree....take your sextant, use it, and may be one day you will really need it.

happy shooting - enjoy your fixes... ( sounds like a drug gang war..)

stephen

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[BrendanS]

Re: Don\'t....

Much discussed on these forums, but GPS time at the satellites is corrected to within microseconds at the receiver end due to the almanac that is transmitted to your gps in the satellite signal.(though there is a minor lag between the 'computer' in the GPS calculating the very accurate time and displaying it of a second or so)

Basically, the time shown on your GPS is accurate to within a second or two of UTC or any local time you select on your GPS. Far better than just about any clock or watch you can buy at any price.

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[SydneyTim]

I assume your friend who keeps a spare GPS keeps it in a Faraday cage, and also has three or four others just in case he gets hit by lightning.

Happenned to a friend in the Pacific and he found land by DR after losing all electrics including the 2 hand held GPS he had on board even though they didn't have batteries in.

Supposedly a lightning strike kills all eletrical circuits whether live or not even if you are onely "near" a strike.

Wouldn't go too far out of sight of land without a sextant and the means to navigate with it.

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[Birdseye]

Thats a good one! Must remember to keep a sextant for when I'm hit by lightning. And several bottles of champagne for the in between times when I win the lottery.

In the real world, a sextant is not only much less accurate but also much less reliable. Can you get a sextant sight at any time of the day or night whatever the weather? Does the gps ever make calculation errors when being thrown about by rough weather, or when tired. Can your sextant reliably work out the bearing of a waypoint? Or the track made good?

Lets be honest - its a nice historical curiosity like the astrolabe, gaff rig, hemp ropes, cotton sails, and semaphore. Or do you still use them?



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[Adrian]

Dont forget your spare sextant in case you drop the first one over the side.


<hr width=100% size=1>Adrian
<A target="_blank" HREF=http://www.kydproducts.co.uk>http://www.kydproducts.co.uk</A>

 

[SydneyTim]

Lightning does happen, but an alternative scenario is a roll over and flooded cabin let's hope the electrics still work. I guess if you're in the Atlantic with no GPS you can just sail East or West until you hit something, or you can take a sextant.

I'm not saying don't use a GPS but if you're crossing an ocean I think it's worth a few quid to have a back up, and it's lot more useful than a whole heap of other things people put on boats in the name of safety.

Acid test if you've got a chartplotter do you still record your position on paper, if you do what's the difference between that and taking a sextant as back up to a GPS?

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[Mirelle]

astrolabe, gaff rig, hemp ropes, cotton sails.....

Cough, splutter.....I do use gaff rig and cotton sails (to be precise the sails are a dressed cotton-terylene mixture, and seem just about indestructible).

No use for astrolabes, hemp rope or semaphore, though.

I also have a sextant in a locker, and a quartz clock. I don't expect to use the sextant in earnest, but since I had one before GPS, and I have a good stowage for it, I can see no point in not carrying it. It is really at the level of "a nice toy", now, but that applies to the whole boat, because yachts are nice toys. The best way to get to windward is in a Boeing 747 or Airbus A 340!

Sextants are nice things to have, and good fun in coastal navigation, too.

More pertinently I also carry a Walker Excelsior towed log, which you will need for GPS-less sextant navigation anyway, and unlike the through hull paddle wheel, which tells whoppers at the slightest provocation, it is unfailingly accurate.

Messing about in boats is just grown up play; the technology is outdated even if you use carbon fibre spars and Kevlar/Mylar sails.

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[bigmart]

Wouldn't this untimely Lightening strike also take out your Electrically Powered watch. Mind you if you can afford a Sextant (Non Plastic) then I suppose you can afford an Accurate Mechanical watch.

I must admit that I would like to obtain a Sextant & re-aquaint myself with how to use it, but only, as a novelty. I use GPS which is more accurate & simple. Both attributes appeal to my nature.

Martin

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[30boat]

Yes,I can also take a spare plastic sextant,and a spare GPS,why not?

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[gjeffery]

Dont forget the 7 figure trig tables and logs or a Facit mechanical calculator. Also a good clockwork deck watch. Better take a valve (or germanium) radio for the time signals; the transistor sets may go down with the lightening.

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[Guest]

Post deleted by danfoley

 

[AndrewB]

It's nice to carry a sextant not just for astro nav but for position fixing using both horizontal and vertical angle measurement. There is a real pleasure in navigating by these old skills. How can people who chose to travel around by wind-power, possible denegrate those who like to use traditional methods of navigation?

However, there really is no need to carry a sextant, not even in case of a lightning strike. I've taken a strike which did indeed fry the fixed GPS, but the cheapo backup handheld stored in my tool-kit was fine. You can have three or four of these backups for the price of a decent sextant.

And the chances of the GPS system being suddenly turned off must now be even less than of winning the lottery.

 

[richardandtracy]

I admit to having a sextant and no GPS.

Why?
I can make a sextant myself, but not a GPS. The only user 'repairable' thing on the GPS is the battery. BTW, I can make lenses from flat glass - did it once (bitumen adhesive to hold the glass, Tungsten Carbide indexable tips on the lathe, plenty of paraffin lubricant & an incremental ball cutting method followed by about 10 hours polishing with jewellers rouge), it's just not worth the effort. So dropping the sextant is not a problem. My main consolation in not having GPS is that a steel boat will bounce off most things if I eventually end up in the wrong place.

Sextant's are not really hard to make - for a fun one see http://www.tecepe.com.br/nav/CDSextantProject.htm
It's a sextant made from a CD and some lego. The very idea'll bring on a smile.

However, when I [eventually] go on my dream voyage I will use a handheld GPS, they're too good to ignore for ever. Just need to find enough pennies lying about in the street for long enough (16p this week, 23p last week.. the fund's already up to a fiver this year).

Regards

Richard.


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[dulcibella]

When your last GPS has fizzled and you've dropped both sextants over the side, remember the final solution. Make yourself a cross-staff out of a graduated bit of stick and take Polaris sights like the Vikings did. These give you latitude directly with no need for tables, so you can get onto a useful latitude and then sail down or up it until you find what you are looking for. Without the correction tables you may be 50 miles or so out, but it's a lot better than sailing in circles hoping God will take pity on you.

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[AndrewB]

Can\'t argue with that!

Some fairly impressive navigation has been achieved with a rudimentary cross-staff. Steve Callahan, the author of 'Adrift', found his way into the Caribbean with one mocked up out of just three pencils.

If you didn't drop your quartz wrist-watch overboard along with all the other goodies, and somewhere aboard you have the diagram of the 'equation of time' (usually pasted in sextant boxes), longitude is even easier and more accurate: just measure the midpoint between sunrise and sunset, and compare the corrected time with GMT, every 4 mins difference = 1 degree. No other instrument required.

 

[Jacket]

Would depend where I was sailing. Crossing the atlantic, if I lost all power and the GPSs, I'm confident of reaching a harbour safely by DR and a long leadline (though I'd probably change my destination for an easier/safer to 'find blind' harbour). From what I've heard of the pacific, with many more hazards, I'd probably prefer to learn to use a sextant just in case, if I was to sail there.

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[tome]

Agree with this Fatipa, there just doesn't seem to be any good reason to not take a sextant and tables. Whilst the GPS is working, it's accurate clock makes it very easy to 'rate' your chronometers, which will remove one of the biggest sources of error.

Like you I've a fair amount of electronics onboard, but like the idea of independence if all goes pear-shaped. Probably the worst failure would be total loss of power (eg batteries drowned or fried) in which case you'd soon eat the batteries in your spare handheld GPS. I've used a sextant to navigate and whilst I'm rusty now I agree it's something you'd learn very quickly in extremis.

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