Forget the Sextant

[Guest]

Charles Reed recently bemoaned the lack of controversy on this forum.

Here then is a heretical thought.

You don't need a sextant offshore anymore....

It just isn't cost-effective. If you are concerned about safety, save the money and buy a para-anchor or a Luke storm anchor instead. Or three more handheld GPS units.

If you have all of these, get some good claret in.

Those who love sextants point out that the electrical system that sustains your GPS can go down - batteries can fail. Sure, but handhelds are the back-up for the main GPS/plotter and plenty of spare batteries should be in every cruiser's inventory in case your handheld batteries fail.

Celestial diehards who make these points often fail to remember that sextants can be dropped too - with disastrous consequences.

Today's GPS units are so absurdly cheap that having a couple of handhelds in addition to the main system is well within the reach of most people - and far cheaper than a good sextant.

What about lightning? Well sure it is a risk, albeit a pretty small one. Lightning could also kill you. I keep one of my spare GPS units in a padded metal box in the oven - Faraday box principle.

The worst that can happen if lightning fries everything - or if the GPS satellite system goes down - is that you then have to do what sextant users have to do whenever its overcast anyway - rely on DR. (Keeping a regular plot on your paper chart is essential, of course.)
I stopped using my sextant offshore nearly ten years ago. Airplane pilots stopped a lot earlier...

Many people who still use sextants freely admit that they do it more for aesthetic pleasure than as a cost-effective means of locating their position. That is fine.

So on next year's W/E Atlantic crossing via the often-overcast Northern route I'm leaving my plastic Davis sextant behind. It takes up too much room in a small Sadler 34.

I suspect that many of those that have sweated away to learn celestial nav feel that others ought to too. A bit like having to learn 13 words of Morse a minute to get a Ham licence. "If I have to suffer why shouldn't others too." This sort of reasoning may be understandable; it is not compelling. (In the US the totally absurd 13 wpm requirement has been cut to 5 wpm.)

It is probably true that those who are competent selestial navigators are - on balance - better sailors than those who have only ever used GPS. But this is because they have likely been sailing longer and have had the commitment to sailing to learn what was once essential.

Andrew

 

[Guest]

Depends how much you trust the politicians.

You are quite correct of course GPS is a very reliable position fixing system unfortunately it is controlled by one set of politicians. Until you can get a set that will pick up both present systems or two of the three proposed systems stick to carrying a sextant just in case. I know if the President said that they would never switch off NAV * but would you trust a cigar smoker.

Anyway I go sailing for pleasure and trying to get a reasonable fix is fun and keeps my brain working

-{)>

 

[Guest]

Have I misunderstood if I read W/E as weekend, and if I haven't, where can I buy a Sadler 34?

 

[Guest]

Re: Depends how much you trust the politicians.

A lot of us who sailed when Long John Silver had two legs and an egg on his shoulder trusted the greatest cigar smoker of them all, Winston Churchill. However, I see your point about the last one, it was what he did with cigars that made me mistrust him!
As for sextants - the most accurate position fix I know of is the horizontal angles and while this ain't much use offshore I think I still prefer to keep one on board to check out the accuracy of the GPS before going out over the horizon.

 

[johnsomerhausen]

I wonder how many of the "sextant purists" go to the length of buying a non electronic chronometer (much less accurate than a simple quartz crystal watch and quite a bit more expensive). A quartz crystal watch could go on the blink just eas easily as a GPS.....I keep my Ebbco Special on board "just in case" but haven't used it in the last five years.
john

 

[Castletine]

Re: Depends how much you trust the politicians.

I didn't realise that Bush was intellectually capable of handling a cigar, especially with a lit end!! (Yes I do know you meant Clinton, but president is portrayed in the present not the past)

I must say that Bush and the 'nuclear red button' is a combination that gives me more heebie jeebies than the cold war ever did.

Listers - I wouldn't be too concerned over GPS v sextant, because there may be nowhere to navigate too!

 

[Guest]

Re: Depends how much you trust the politicians.

Isn't that a bit like using a sundial to check the accuracy of your chronometer?

 

[Guest]

Horizontal angle fix makes G PS

look like it's been measured with a bit of wet String with Knots in it


That is why and D GPS was invented and even that did not have the accuracy of 3 charted positions measured to a tent for a minute. I don't know if it's changed but survey work was a was done using horizontal fixes either electronic or if they wanted to be really accurate using a sextant.
Try it some time sit on it a triangulation point ashore and compare the difference between where the GPS says you are and a horizontal fix using a sextant on three other trig points. And you will see how inaccurate GPS is!
But then how at front you need to know your position plus/ minus half the visibility is the usual required accuracy at sea.

-{)>

 

[roger]

what about navigators eye? If you look throught the telescope on the sextant with not enough filters you burn out bits of retina. It's a real professional hazard.

 

[alant]

While agreeing with handheld GPS as back up, check next time your sailing how quickly (or not) you can aquire any satallites. Easy with a hand held, to get blanked off from a good signal, either by the mast & certainly by any sails.
Ideally use your fixed units aerial, otherwise you will still be relying on your last fix (assuming you plot them).

 

[Guest]

Re: Horizontal angle fix makes G PS

I don't sail ashore very often! Within sight of land I often use a hand bearing compass for a bit of variety and to second guess my GPS, but GPS always wins. Over the last ten years I have found GPS to be accurate to within a few boat lengths. I was cruising in the Caribbean during the Gulf war when the US switched off selective availability so they could use civilian GPS units in the desert - the accuracy was amazing! But, as you say, how accurate do you need to be - and how accurate are the charts on which you plot the position? Someone else on this thread mentioned sails effecting the accuracy of a handheld GPS - I didn't think this was possible, and it is not something I have ever experienced. Human bodies can block out the signal, but fibreglass and fabric and wood - I didn't think so.