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Old 12-02-2011, 17:48   #16
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I suggest a better investment is to learn emergency navigation first, which I think is more practical and more grounded in the whys and hows. It will also serve you much further. And for this there are a number of strong books on the subject if you want to get going.

Having relied on sextant a bit, I can tell you its not very reliable as weather/visibility not always your friend...especially in the north atlantic. Actually, its a down right pisser and I think a waste of time. But, if you are still keen on learning, there are plenty of books on the subject. I don't think a mentor will add that much. Your sun and lunars are your friends which is basic and rather simple. Stars, planets...well, you need a good clear horizon and hopefully someplace away from city lights, buildings etc on a sunrise/sunset which may not be available. Everything else, such as latitude by lunar distance etc is geek crapola
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Old 12-02-2011, 17:48   #17
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Originally Posted by Eleebana View Post
What I want to know is what percentage of cruisers out there don't even have one on board or if they do, could not reasonably navigate home with it anyway?

Come on, it's me your talking to so tell me the truth.

Greg
In addition to my comment above, so far I have had no dramas coastal cruising using a handheld GPS and dead reckoning. It is not hard to pick most landmarks on the East Coast of Australia and if you head west you are inevitably going to find one (or maybe even run aground and flounder?).

The real reason I am keen on a sextant is so that I can confidently set off over the horizon knowing I will always be able to find my position and landfall. While the GPS is still operational it would be fun on long passages to get the sextant out and compare results until I had the thing mastered.
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Old 12-02-2011, 20:35   #18
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Hmmmm ... light disappearing ... real bad.

Here in Canary Islands we still have a handfull of lighthouses. Convenient. Otherwise hard to miss the land - one can see the light of the city two nights before the landfall ...

However, we make our landfalls by the GPS. So if there is no GPS and no lights and marks ... hmmmm, REAL BAD!

Drift, drifting, drifting ... gone.

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Old 12-02-2011, 21:06   #19
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Barnie.... I was thinking of the North Sea and the Thames Estuary where there's loads of sandbanks... and other places like the Channel Islands/Greek Islands where there's quite a few rocks around... not everyones got radar and not all rocks are above sea level...
A lot of stuff works on waypoints programed into the GPS/plotter so bouys are no longer needed and survey results are posted as updates to download.... but if the old nav marks have gone and your GPS is no longer there your down to 'eyeball' sailing in the daytime....
When I passed through the Greek Islands I discovered the owners C/P did not go East of Sicily.... I had the latest passage charts (bought in Almerimar on the trip) but soon found 50% of the marks were either missing or not lit between Spain and Pendik in the Marmara... city lights are fine.... but.. I don't know about you but I find night approachs very wearing... bad enough trying to figure out if the flashing light is a disco or traffic light... or is it the port marker...
Nope... reckon there'd be a lot of sailboats hove to around a lotta ports till dawn..
Its okay folks... Phils rambling again...

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Old 12-02-2011, 21:37   #20
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Thames ... have not been. Have been up north - Fraserborugh, Inverness (got stuck on a bank and later the same day hit underwater larsen wall ...

And only to imagine the same waters with fewer marks ;-(((((

Ouch!
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Old 12-02-2011, 23:23   #21
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I own an Astra IIIB, a Freiberger Yachtmaster and a Davis plastic one for my son/the liferaft.

I get pleasure out of the math and the craft.

We are still on Lake Ontario. I manifestly don't need one...it's hard to get out of sight of land here.

However, I have used in in pilotage (on its side to get really nice bearings, or to estimate height of shore features). Again, yes, I have and use GPS, but I suppose there's a reason people still drive stick.

I feel fairly strongly (strongly enough to buy almanacs every year) that sextant use connects me with the environment through which we plan to voyage, and while the "where are we" skill set is obviously primary, recognizing the navigational stars and knowing right when noon is has elements of ritual and comfort I enjoy, like splicing and whipping line.

In light of the comment that nav aids are not as always maintained as we would hope in the real world, I can see that seeing a red buoy on the plotter...and NOT seeing it in front of you where you expect it to be...could be disorienting. Having the paper chart of Landfall X and being able to take accurate bearings, however, removes all doubt. You don't need the nav aids if you can determine your position, but the disconnect of what the plotter is displaying to what you can see could lead to doubt, confusion, and possibly error.

Just my viewpoint. I don't really care if anyone uses a sextant besides me. It's another tool in my box.
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Old 13-02-2011, 07:29   #22
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There are ways for astro navigation without sextant too. It takes a good watch and almanac tables and accuracy varies with latitude and time of the year. But the methods are supposed to be good enough for emergency purposes.

The point is, people who want to know who DOES NOT use the sextant will also NOT be interested in other alternatives.

I have noted elsewhere on the forum that many of the sailors who do not care for the sextant will (accidentally?) have poor knowledge of the use / uses of the GPS too ... my guess is some people are technical and love toys (sextants, logs, watches and GPS units) others are not.

Many people will claim "I can go by my GPS alone" then the next thing you see is they do not know how to enter a WPT into the unit. I can use both instruments and I can get an intercept from a GPS (no satellites attached) too.

Some general terms and conditions apply ;-)

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Old 13-02-2011, 08:15   #23
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Have a sextant, a compass (3) pelorus, handheld gps, chartplotter, depth sounder, lead line paper charts etc.. I do not know how to use the sextant, the other person aboard does. We both know how use all the other stuff aboard, and regularily use DR on the paper charts, as well gps positions. no good having the paper if you dont mark positions when sailing, if gps goes out, what reference have you left yourself with. Oh dont forget the trusty log book. Use as many things as you have available, keep in practice with the ones you have. At least that is how we operate.
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Old 13-02-2011, 09:15   #24
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I have never seen a sextant on a boat since the early 1980's.



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Old 13-02-2011, 09:54   #25
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Unless you use one fairly regularly, leave it at home. i learned how to use one back in the 60's and years later tried unsuccesfully to get a noon sight... just too rusty! Made me mad so I refreshed my memory and enjoyed playing with it about once a week which really refreshed my skills. With all the new gismos for navigation available, a sextant really doesn't top the list. However, when things go south powerwise, it is comforting to know I've got a backup and the ability to use it. Takes a fair bit of practice though. It is a kick to haul it out with friends aboard and actually plot a position! Cheers, Capt Phil
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Old 13-02-2011, 11:39   #26
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Seems to me that if one is carrying a sextant for backup then one should not be relying on calculators, computers and other miracle equipment as part of the process. What do our paranoid-pessimist* CF friends think?

(* I mean this will all respect, as they will be the ones I'll be searching for when GPS falls from the sky.)
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Old 13-02-2011, 12:27   #27
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There are a variety of forms available that require only addition and subtraction and the inputs from sextant, clock, almanac and HO229/249 and Table 5, etc. for the fine tuning.

You can find your latitude fairly closely with sextant alone, of course. Just figure out local noon by finding the "highest" position of the sun.

Add a clock and almanac, and go further. It could be any almanac, if you just need rough position. If you have a known position and have kept DR estimates, you can verify pretty well.

Take calculus and you can do all this stuff without the tables...but it takes a long time.

So the calculator is really the equivalent of a dedicated oven mitt in terms of producing the cake of a plotted position. Most people use a couple of tea towels, regardless. I still see sextants on boats, but not the calculators.
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Old 13-02-2011, 12:40   #28
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You can find your latitude fairly closely with sextant alone, of course. Just figure out local noon by finding the "highest" position of the sun.
Of course, this only works about four days of the year. The other 361 days you'll be wanting an almanac and at a calendar. Be a pitty to be off by 23 degrees of latitude.
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Old 13-02-2011, 12:45   #29
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Yes, one can solve the fix with reduction tables, and without such tables just from the formulas. However, without reduction tables, it helps to know how to use logarithms to avoid multiplication of long numbers and avoid possible errors.

My manual method is:

a) by reduction tables (not the full ones only the abridged ones), or else
b) from formulas, by Casio.

I can use the log tables too but I tend to make errors when using logs due to lack of sufficient exercise in this respect.

But again - the thread is who DOES NOT use / have the sextant. So appologies for the drift.

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Old 13-02-2011, 12:56   #30
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Of course, this only works about four days of the year. The other 361 days you'll be wanting an almanac and at a calendar. Be a pitty to be off by 23 degrees of latitude.
But can tell your latitude from the duration of the daylight, without a sextant too.

(Read about it, but have not tested how practical it is).

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