Been looking at the ARC

[Becky]

website, longing to be out there. Like Stellagirl. But, I did my Ocean theory absolutely ages ago, and I can't remember the stars or the business with a sextant. Now I know we all have GPS, but everyone always says 'what about a power cut' (or words to that effect, you know what I mean). So, should I learn to use one of these things again. Do any of you actually have a sextant on board?
And if so, is it for decoration or can you use it?

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[john_morris_uk]

If you learned once I suspect it would come back to you fairly quickly in extremis.

Long ocean passages can be tedious - I often get the sextant out merely because I am bored - nothing to do with batteres giving up.

Even if the whole boat electrics fry, why not carry a hand helf GPS with some spare batteries? Just turn it on once a day long enough for it to find itself and fix your position on the chart. When you are travelling thousands of miles and you are hundreds or thousands of miles from land who cares where you are at any particular time? You certainly don't need to know your exact pos every second of the day....

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[Gunfleet]

I thought about getting one. Then a pal told me he and his wife had done the course and were able to calculate their position to within ten miles with a sextant... standing on a beach. So I bought another gps and keep it in a biscuit tin in case of lightning.

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[StellaGirl]

They gave a lecture on the use of sextants last year before the ARC started. Did I go? Well it was sunny, hot, beer was cold and the lecture was inside.....
Perhaps I should have done but from what I heard people didnt learn that much.
As for GPS, if the power went we had 3 handhelds between us and put them in the oven during the electric storm we had!

<hr width=100% size=1>Its 11.59am - lets open the beers...

 

[Talbot]

Yes have a sextant (1944 Husun), yes have used one before (many years ago) doing a refresher Yachtmaster Ocean at Chichester College at the moment. I would be ashamed to be as inaccurate as 10 miles on the beach - whereas in a bouncy boat would be a different matter.

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[LadyInBed]

On a coastal passage, I get mine out to play with occasionally, but I only play with it in its horizontal mode, never when it’s vertical /forums/images/icons/blush.gif

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[tome]

Becky

As you possibly know I work intimately with GPS and use it both on the boat and for professional applications. It has some vulnerabilities which aren't obvious and would take an age to explain in detail. It is under US military control. There's a USSR equivalent (GLONASS) and soonish a European constellation (Galileo). China are amongst the subscribers to Galileo funding and the US has reserved the right to take out our satellites if threatened.

I keep a sextant just in case, and can tell you emphatically that no power on earth has the ability to take out the stars. They are there for free, and you will gain tremendous pleasure from working an Ocean position derived from stellar and planetary observations. It's immensely satisfying and you won't give a jot whether your position is accurate to 1 or even 10 miles out there.

That said, I also carry a spare handheld GPS.

Tom

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[Gunfleet]

<<That said, I also carry a spare handheld GPS.>>
You scallywag.

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[ShipsWoofy]

When I was in college in 87 doing marine engineering some bright spark thought it would be a good idea for the grease monkeys to learn a bit of bridge work and vica versa.

Every wednesday morning we would be bored to death by some old man who had spent far too long at sea teaching us astro navigation, zeniths, azimuths yawn yawn.

One particular day this tome of an almanac landed on my desk, star charts for the sextant or summit. Well that was enough to kill my interest forever. But now I actually do have an interest.

How long would it take to pick up the technique, how big a library do you need to carry to plot a position, can I teach myself or are there short term courses?

Is the only viable training the RYA Oceanmaster?

<hr width=100% size=1><A target="_blank" HREF=http://www.topcatsail.co.uk>All New website</A>

 

[snowleopard]

bought my sextant and used it in earnest back in the 70's when you could buy a luxury yacht for the price of a satnav set.

i still carry it on board, along with all the publications but am generally too busy/lazy to get it out on passage. i designed myself a sight reduction form which reminds me how to do the calcs so i can get back to it with only a little practice.

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[tome]

It's really quite easy, and most people could master a sextant on a 2 or 3 day passage. It's also a lot of fun and I'm sorry to hear you were bored by a bufoon who was obviously more intent on impressing you with his knowledge than teaching you a simple skill. You only need 3 books;

1) Nautical Almanac for the current year (not MacMillans/Reeds etc)
2) Sight reduction tables
3) Tom Cunliffes book on astro nav

Blank plotting sheets help also, you don't need any detail mid ocean. You certainly don't need to do an RYA Ocean course.

And don't call me a tome of an almanac again or else I will land on your deck.



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[jonjo]

I learnt sun-run-sun astro from Mary Blewitt's slim book over a 3 day period at home before departing for the first ARC back in 86.

A cheap £35 Ebco sextant was enough for my fun astro at sea comparing against the SatNav. My results got better once I adopted the practice of letting my budget plastic sextant warm up out of its box before taking sights.

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by jonjo on 23/11/2004 00:44 (server time).</FONT></P>

 

[Robin]

We have one, albeit an Ebco plastic one, plus the tables needed as well as a Casio programmable calculator with pre loaded almanac and calculation program (laboriously typed in by me one winter from PBO articles) and another simpler program on the laptop. Like Snowleopard I also designed my own sight reduction forms to use which hopefully will wake the memory up if I wanted to do so! It isn't actually on board these days as it didn't find a place on the new boat when we moved everything over, but we did play with it previously from time to time and could get quite a reasonable plot (within say 1ml). I will admit though to cheating by using the GPS clock for the time element of the calculations. When/if we finally get to break away from the work prison it will get a ride on board if only to guarantee that the GPS sets behave themselves!

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[snowleopard]

using the GPS clock isn't necessarily cheating... if you have a quartz clock you can check it using the GPS time so that if the GPS dies you can extrapolate the error and work out the exact time. a lot easier than messing about with WWV time signals!

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[Robin]

In practice that is what really happened, I checked my quartz wrist watch against the GPS then used the watch for the time. The PBO Casio program is really good too and apart from actual sight reduction we used it for suns bearing to swing the compass in conjunction with a plastic pelorus/shadow pin.

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[tome]

Rating all timepieces against the GPS clock is very useful. I check both our clocks and note the time drifts on a daily basis in the log if on a longer passage.

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[Talbot]

costs:
Sextant £70 - £500 dependent on quality (ebay prices)
Nautical almanac - abt £25
Rapid sight reduction tables (2xvolumes) £50
Tom Cunliffe's book -£10
Plotting Sheets - download from (here)

+ practice.

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[Sea Devil]

I still have my sextant on board but for the first couple of years after I had GPS I got it out and practiced - Now cannot be bothered. Have 2 gps on board (minimum for ocean sailing) and my DR is good enough to get me in for local sailing. Log my GPS pos every 4 hours.
Really sad but I really think a sextant is a bit like a RN officer - the last think you want in a sail boat...

<hr width=100% size=1>If you have time please visit my web site -
<A target="_blank" HREF=http://www.michaelbriant.com/sailing>http://www.michaelbriant.com/sailing</A>

 

[snowleopard]

costs

all the costs listed are one-off except for the nautical almanac. i would be reluctant to shell out each year for a book i might use once in its lifetime. i have an old dos-based program that can print out a facsimile of the almanac pages a month at a time. i print off the relevant dates before i set off on a passage or i can print them while under way if need be.

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[Koeketiene]

a sextant is a bit like a RN officer - the last think you want in a sail boat...

Thanks - made Mrs Yanita smile tho

<hr width=100% size=1>Experience is a good teacher, but she sends in terrific bills.