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Old 17-02-2010, 12:19   #31
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Originally Posted by daddle View Post
No problem whatsoever. I'd know what latitude I as at when gps quit. Simply keep sailing towards paradise. Bound to find something. I'd ask the locals where they are when I get there. That's real sailing.
Some issues to consider:
1) most 'pure-gpsists' never bother to take down the gps readout, so you would likely NOT have a fix to start your DR,
2) the Pacific vision of paradise is very, very tiny islands in vast, vast ocean - you may miss your paradise, or even worse - hit it,
3) even if you know your exact fix say 1000 miles off your destination, getting there by DR is next to impossible,
4) if it were (that simple as you bid) sextant would have never been used by sea navigators ever since it was invented and into today.

Apparently, 'real sailing' is a movable feast.

b.
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Old 17-02-2010, 12:22   #32
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I found ones that have bigger graduations are easier to work with. A plastic Davis Sextant can be just as good as an expensive one. It takes time to get used to using a sextant when a boat is rolling and pitching. Old, used sextants often have play in the mechanism which can make a differnce to your readings.
A sextant that is light and easy to operate and lots of practice is what is required.
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Old 17-02-2010, 12:27   #33
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Reasons not to have a sextant:

1-If you drop it, it is toast.
2-Will tie up $400-800 or more, depending on your choices.
3-Requires some skills and either a sight reduction program/calculator, or tables

If you get a sextant, it is for intellectual exercise, like playing chess. Sure, the government could turn off GPS, the Chinese could shoot 'em all down, or the kids next door could jam it but let's come back to "If you drop the sextant" that's the same problem, isn't it? So now you need a backup sextant as well...Which will cost you as much as 2-4 GPSes, that usually still work well after being dropped.

I'm not against sextants (or chess) but as a practical matter, if the entire GPS system GOES DOWN, I suspect I'll have bigger issues, like trying to avoid warships and find a safe harbor. If all else fails, I can still figure out the compass directions and find land that way.
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Old 17-02-2010, 12:35   #34
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1. What would you recommend as a good starter/learner sextant?

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?
1. To learn the rules, to exercise, nearly any sextant is OK. The better the sextant, the more fun learning. But for real life use you will need the real thing, which means another investment. Now ask yourself if it is cheaper to buy two sextants or one.

2. Same like buying a boat on Ebay. A sextant is a precision instrument and it is good to check it out before buying.

3. Do not forget them Ruskis did fly into the space first, and put the first satellite out there. (But I bet a Russian sextant will be heavier than a modern alloy thing). And it is true that many a Russian technology is copies of Western stuff (so you may end up with a C&P clone at a fraction of the original's price!).

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Old 17-02-2010, 13:13   #35
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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!
I bought a used plastic Davis Mk25 off ebay for $85 and learned with it.

Then I bought a absolute mint Tamaya Spica (a beautiful piece of instrument and a joy to own) off ebay for under $400.

I sold the Davis on Ebay for $175. (Yeah, it was a bit of luck on my part, but the European buyer was very pleased).

Patience and knowledge (research) are the key if you want to buy off ebay. Always use Paypal, as you can get your money back in case your purchase was not as advertised.

The Chinese made Astra IIIB is a good Sextant and can be found used in the $300 range, while they are $600 new. Other names to look for are Plath and Tamaya. I have no knowledge of the ex US Navy or Russian models, but noted that their built in error was pretty high on all the ones I researched.

Start with Marine Sextants | Celestaire, Inc. and get an idea of what you need and the top end of retail prices.
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Old 17-02-2010, 13:47   #36
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I would advise care with second hand sextants. Theres no way to determine if it has been knocked out of alignment. ( Often this is why they are being sold). I have a astra IIIB ( bought new), still find its hard to get better then 5 miles whedn taking sights on a small boat.

I wouldnt buy a sextant because of suposed GPS issues, more that you find it interesting, becuase otherwise youll stuff it away and probably forget how to ue it in an emergency. Its takes constant use and practice to become ( and remain) compentent.

PS: currently teaching myself longitide by lunars, very interesting, so will be able to cope with no time signals. ( mind you need teh internet to get the tables!!)
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Old 17-02-2010, 14:00   #37
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Amazon.com: A Star to Steer Her by: A Self-Teaching Guide to Offshore Navigation (9780870333095): Edward Bergin: Books
this is the book I used to learn from. bought a cheap plastic sextant and a used german built one from 1974 from an antique store that is awesome. learn to do it. it's fun and fun to compare to your GPS readings. you'll notice with practice you'll get better and better and it's always a conversation piece when you whip it out for others to look at.
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Old 17-02-2010, 14:06   #38
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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
I had the same question...any thoughts or recommendations?
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Old 17-02-2010, 14:14   #39
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can't agree with the conjecture here

Quote:
Originally Posted by barnakiel View Post
Some issues to consider:
1) most 'pure-gpsists' never bother to take down the gps readout, so you would likely NOT have a fix to start your DR,
This claim is contrary to my experience. I've helped a great variety of people with deliveries, and I can't recall a single instance where the lat/lon wasn't logged at least once by each watch. Admittedly, I don't crew for yahoos, but it seems that even on boats where paper charts are not actively being consulted, the fix is being recorded on a regular basis.

On my boat, the fix is recorded every hour on the hour. Isn't this how most folks tend to navigate these days?

Alternately, when I've done passages with sextant guys, they seem content with the daily noon sight. (Which is fine with me, pure GPSist that I am, so long as I don't have to help with the math.)
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Old 17-02-2010, 14:16   #40
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I have no knowledge of the ex US Navy or Russian models, but noted that their built in error was pretty high on all the ones I researched.
This error is no problem, if it is known.

There are good sextants from former East Germany too. Mine was less than USD 200 s/h. It is very good (below 2Nm error in test conditions and usually below 5Nm in real life on a rolling 26' boat.

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Old 17-02-2010, 14:41   #41
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Any sextant if far more accurate than the sighting process. Plastic works fine.

In my experience the rarity of the right condition occuring makes sextants useless: cloud cover, indistinct horizon, rough seas. However the process is very cool.
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Old 17-02-2010, 14:48   #42
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Originally Posted by barnakiel View Post
Some issues to consider:
1) most 'pure-gpsists' never bother to take down the gps readout, so you would likely NOT have a fix to start your DR,
2) the Pacific vision of paradise is very, very tiny islands in vast, vast ocean - you may miss your paradise, or even worse - hit it,
3) even if you know your exact fix say 1000 miles off your destination, getting there by DR is next to impossible,
4) if it were (that simple as you bid) sextant would have never been used by sea navigators ever since it was invented and into today.

Apparently, 'real sailing' is a movable feast.

b.
I meant that having GPS fail is not such a big deal in an otherwise well managed program. Not serious like a rudder or rig failure. Sextant buyers might first carry a real spare rudder before buying into the sextant 'hobby'. Rudders fail far more often than GPS.
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Old 17-02-2010, 14:59   #43
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Any sextant if far more accurate than the sighting process. Plastic works fine.

In my experience the rarity of the right condition occuring makes sextants useless: cloud cover, indistinct horizon, rough seas. However the process is very cool.
Yes - taking a sight from a rolling yacht results in considerable error. But there is no reason to add other errors on top of what already cannot be avoided. This is exactly why we want a sextant with maximum accuracy and may opt a plastic one out. (But it is better to have a good plastic sextant and know how to use it than go without any, IMHO).

In my experience taking sights is possible often enough to be able to rely on DR in between. This holds true for the easy round the world route. I believe that say in the N. Atlantic route from the US to England there may be long periods when taking a shot is not possible.

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Old 17-02-2010, 15:18   #44
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Rudders fail far more often than GPS.
???

Any hard data on this opinion?

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Old 17-02-2010, 15:25   #45
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i do not know how to use a sextant,how ever i do keep a log of my GPS position and i carry 3 of them.When i finally get my last kid off to University,i shal head out to the oceans,but before that i will learn how to use a sextant.I often switch off my GPS and use compass along with tidal set and bearings etc to plot my course.I have had the experience of loosing my electronic navigations systems,the chartplotter got too wet and the old gps that i had struggled for some reason,so i regularly practice non electronic navigation techniques.I find it enjoyable to sit down at the chart table and plan the journey

There was a guy in the UK who passed away in december 2009,his name was Mike Richey,he was a real stalwart of the sextant and often would persuade the museums to loan him a sextant so that he could use it for real,the chap was a master of celestial navigation,he was in the middle of the atlantic in his 21ft junk rigged boat and a passing cargo ship through him a message with his lat and longs on it,mike was most displeased with the guys.

The sailors who are going out and singlehandling their boats on Ocean passages all have sextants.

The price of a new sextant over here starts at 159.00 gbpounds for a davis 15 to 539.00 pounds for one by Cassens and Plath
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