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Old 17-02-2010, 07:13   #16
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For me its just plain satisfaction in fixing a position without relying on electronics or batteries, especially fixing a position using stars.
Sextant I have is now 75 yrs old, left to me by my Dad, its not the easiest sextant to work, has a vernier scale rather than a micrometer, and needs a magnifier to read the vernier, but thats half the fun, plus its good to look at.
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Old 17-02-2010, 07:26   #17
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Basile, see the link I posted in this thread above and scout thier site. They have courses and books and even less expensive sextants. The principal is very simple. trianulate from possitions of known refference to fix your possition. The same as gps or compass readings from known objects. The practice is a bit more invoved primarily because the objects are moving and outside our atmosphere so there is math which can readily be done with calculators, programs on your computer or even tables (which is a good thing to learn how to do because there might be a time in which you have your sextant but not electric-a liferaft for instance, many keep their first, less expensive sextant in the ditch kit..). On land to get a feeling for it and practice doing the math, you can even use a protractor and a string with a weight on it for your sightings although a far cry from the accuracy of a sextant.
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Old 17-02-2010, 07:33   #18
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Also, as with everything else navigation, read Bowditch. You can find Bowditch practical navigator on line. Down load it, print it, have it, learn it! That would be an accomplishment for anyone!
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Old 17-02-2010, 07:57   #19
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Quote:
Originally Posted by fishwife View Post
The European satellites are slowly coming on line...
P.
the first TEST-satelite still has to be launched ...
before having a working system it is gonna take many more years
AND
actual equipment is NOT compatible ...
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Old 17-02-2010, 08:15   #20
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I don't really believe that the GPS system is likely to have a long lasting catastrophic failure.

By that I mean a failure where your position is off by more that 10 miles for a couple of days. If you have a modern GPS unit it will have RAIM and that will warn you of possible errors. If the unit just quits working you won't have any doubts.

Now I assume that the prudent navigator on an ocean passage will be keeping a logbook, with the GPS's lat and lon and also heading, speed and distance. So if the GPS dies, you can continue a DR track from the last good fix. This is exactly what you would do for celestial nav if you have a couple of days of cloud cover and can not get a sight in.

Having said that celestial nav is a fun exercise that really isn't that hard to learn. ( maybe if you are math phobic, but you really don't need to understand why the math works, just following the steps in a cookbook fashion. )

Here are a couple of good links: ( somebody asked earlier )
Celestial Navigation Basics
Celestial Navigation
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Old 17-02-2010, 08:37   #21
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you are right zydecotead

we are probably far of catastrophy and good sailor should be prepared to every situation

thanks for your links

that said, being used to compute ... isn't there any software where you can just put in the sextant readings and that just does the calcs to give you a position ?
I know the computer may break down (even if there are 2 extra backups on board) but I am just trying to make life easy in case of a gps-receiver breakdown or satelite-disaster ...

Bas
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Old 17-02-2010, 08:53   #22
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Knowing celestial makes you a more rounded mariner. Sailors are inherently connected to what is happening in the sky. Its a whole body of knowledge that is worth learning. Not learning celestial is much the same as a sailor who goes to sea but has no interest in learning about the oceans creatures. Its right in front of your face...why not learn about it and make cruising all that more interesting?

I think there is a degree of self-satisfaction in having a hand on a body of knowledge that most people have no clue about, including many fellow sailors.

Celestial is not just for getting a fix. It has other uses such as determining sunrise, moonrise etc. You can also use celestial to determine compass error. Try doing that with a GPS at sea.

I think those who have no interest in learning about the skies and how to navigate by the stars are missing out on a number of things that could make their cruising much more interesting.

Is celestial necessary? That's debatable. Will it make cruising more interesting? Absolutely.
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Old 17-02-2010, 08:54   #23
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Celestial navigation appears difficult to learn because for many centuries ship's Captains wanted it to appear as "magical" as possible in order to keep the riftraft crew in their place. Mutiny was far less likely if the Captain and 1st Officer about to be set adrift in a lifeboat were the only ones that had the "mystical knowledge" to find land.

Of the four books I bought on the subject, the best was "Self Taught Navigation" by Robert Kittredge, from which I borrowed the above.

Amazon.com: Self-Taught Navigation: Ten Easy Steps to Master Celestial Navigation (9780873584968): Robert Yates Kittredge: Books

Kittredge explains "how to tell time withhout trying to teach you how the watch was made".
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Old 17-02-2010, 08:59   #24
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Quote:
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Also, as with everything else navigation, read Bowditch. You can find Bowditch practical navigator on line. Down load it, print it, have it, learn it! That would be an accomplishment for anyone!
Bowditch is one of my favorite books, just open it anmywhere and you'll find something really interesting to read.
However, Bowditch is a very large book and printing it would be a mionumental task. You can get a copy from Amazon for $30.

A sextant, like most of the earlier navigation tools, was intended to get you close enough to wherever you were going to enable you to pilot your way in using visual sightings and bottom readings. Even on a big ship if your position using the sextant was half-a-mile off you were doing well. On a small boat in a seaway, getting a good sight takes lots of practice. In fact you'll probably want to take multiple sights to make sure at least one is near-accurate. (Compare it with your dead reckoning plot or your GPS reading and throw out the ones that are way off). The math itself is not hard unless you want to forego the sight-reduction tables and use spherical trigonometry instead.
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Old 17-02-2010, 09:14   #25
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Funny, I just responded to a near identical thread in a different forum. Why do people get so hostile about GPS and sextants? I will use whatever works on my boat. If it is a GPS fine. On a incredible moonless night I may want to back it up with a sextant fix. Heck, I am even thinking about getting a cheap AM radio with a directional antenna. I just need to remember that nothing, even my own eyesight, is 100% foolproof.
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Old 17-02-2010, 10:30   #26
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True. The government also controls WWV time service which you'll need to compute longitude.



Again, true. GPS service was interrupted for 15 to 30 minutes, depending on the type of receiver. Just about enough time to take out your sextant, take a sun or star sight (provided it isn't cloudy), get your nautical almanac and sight reduction tables (produced by the same government--or do you trust the Brits more?), calculate your position, and plot it on a chart based on some government's soundings.

The US government trusted the brits charts more than their own in the pacific during WW2

You may have heard of a brit called captain cook,he ended up as dinner for the natives but he could navigate and he produced charts that are still being used today

Wonder what he would have thought of a sailor who could not use a sextant?
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Old 17-02-2010, 10:59   #27
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Newt,

I think people get hostile to the idea that a sailor who does do celestial navigation is not really a sailor.

bastonjock's post is a very timely example.

Quote:
Originally Posted by bastonjock View Post
Wonder what he would have thought of a sailor who could not use a sextant?
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Old 17-02-2010, 11:09   #28
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I learned to use a sextant cause it was the only game in town. But sextants are wildly inaccurate compared to GPS and make navigation a lot easier and sailing coastally or offshore safer so I use GPS. Taking a good sight with a sextant took me a while to learn and is a skill I intend to keep up besides doing the math is fun but I would never use it to navigate unless I had to.
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Old 17-02-2010, 11:41   #29
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I have had sextant now for30 years and won't part with it. It helped me accross the Atlantic and through the Carribean. In the carribean I bought a Satnav, which has been out of date for years as well. The only things I did get rid of over the years are my sight-reduction tables and my little NC77 pocket calculator. As far as calling someone a sailor only because he has or knows or knows not how to handle a sextant.... that's reaching a little. Find the Timor Islands like Capt. Bligh did.... that's sailing.
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Old 17-02-2010, 12:11   #30
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I have found this thread very interesting and informative. The "romance" of shooting a star and caculating your location have always piqued my interest. The links everyone has posted are very nice ... Thanks to all.

A couple questions from a newbie:
1. What would you recommend as a good starter/learner sextant? Keeping in mind that my money tree has yet to bloom ... I saw some very inexpensive (cheap) plastic sextants but figured that would harm accuracy ...

2. Ebay has several used sextants. Is there anything that would make buying a used sextant more risky that buying anything used, sight unseen?

3. I saw several of the world's navies sextants for sale ... assuming I am comfortable with Soviet workmanship and and can translate cyrillic is there anything inherently different about a non-english sextant?

Thanks again for sharing your knowledge ... fair winds!
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