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Old 13-04-2018, 10:23   #166
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Re: Thorny subject: Sextant and GPS era

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Originally Posted by james247 View Post
Standing on a wharf you can do better then one mile. Standing on the deck of a 40footer in 3 m of the 5 miles would be exceptional
would have been appalling weather if I'd been 5nm off!
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Old 13-04-2018, 13:49   #167
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Re: Thorny subject: Sextant and GPS era

I feel I am blessed by being old enough to have had the experience of navigating to Tahiti and several of the landfalls on the way there, by celestial nav (and WWV time signals) before GPS was available. Seeing Nuku Hiva come up on the horizon after 23 days, where and when I predicted using only celestial nav, gave a tremendous and unique feeling of accomplishment.

But for the last many years I've been trying to figure out what to do with my two Davis plastic sextants (from my father, he taught navigation courses) in good useable condition - I have a "real" sextant and don't need these. Advertisements in the local sailing rag got zero response even for a basic giveaway price. Although folks talk about learning celestial, it seems like few are willing or able to spend the time to learn the craft.

So, you all know how to reach me if . . .
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Old 13-04-2018, 14:01   #168
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Re: Thorny subject: Sextant and GPS era

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would have been appalling weather if I'd been 5nm off!
If you only get a one-body sight and have to cross it with a 6 hour old DR track, then yes, 5mi is about right in rough seas. But a good 3 star sight should be accurate within 1 or 2 miles for the average person in reasonable weather. These levels of accuracy are just fine, since with celestial you are seldom navigating in poor visibility. Anything closer to land then you must be on visual bearings and depth sounder.
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Old 13-04-2018, 14:12   #169
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Re: Thorny subject: Sextant and GPS era

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But for the last many years I've been trying to figure out what to do with my two Davis plastic sextants (from my father, he taught navigation courses) in good useable condition - I have a "real" sextant and don't need these. Advertisements in the local sailing rag got zero response even for a basic giveaway price. Although folks talk about learning celestial, it seems like few are willing or able to spend the time to learn the craft.

So, you all know how to reach me if . . .
Well which Davis sextants have you got and how do you fancy selling them to someone 1/4 of the way around the world for a fair price incl postage? I would actually prefer a plastic sextant due to cost rather than an expensive metal one.

Pete
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Old 13-04-2018, 14:28   #170
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Re: Thorny subject: Sextant and GPS era

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Originally Posted by waterman46 View Post
I feel I am blessed by being old enough to have had the experience of navigating to Tahiti and several of the landfalls on the way there, by celestial nav (and WWV time signals) before GPS was available. Seeing Nuku Hiva come up on the horizon after 23 days, where and when I predicted using only celestial nav, gave a tremendous and unique feeling of accomplishment.

But for the last many years I've been trying to figure out what to do with my two Davis plastic sextants (from my father, he taught navigation courses) in good useable condition - I have a "real" sextant and don't need these. Advertisements in the local sailing rag got zero response even for a basic giveaway price. Although folks talk about learning celestial, it seems like few are willing or able to spend the time to learn the craft.

So, you all know how to reach me if . . .
I’m in San Diego gearing up to teach a CelNav class.

I was going to buy several Davis-3s but might be interested in a couple of -15s if the price wasn’t too much more than a -3 new. I make it to the Bay Area occasionally or we could arrange something here if you come this way on your way to your boat.
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Old 13-04-2018, 15:27   #171
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Re: Thorny subject: Sextant and GPS era

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Interesting to note that the US Naval Academy does not teach CELNAV any more, the Brits do, they are more traditional. Warships carry numerous GPS systems so less chance of them losing a position.
I carry a German Frieberger; however, my cruising days are over if anyone is interested in purchasing.
Actually, the US Naval Academy brought back celnav instruction in 2015:

Charting a New Course: Celestial Navigation Returns to USNA
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Old 13-04-2018, 15:36   #172
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Re: Thorny subject: Sextant and GPS era

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Originally Posted by waterman46 View Post
I feel I am blessed by being old enough to have had the experience of navigating to Tahiti and several of the landfalls on the way there, by celestial nav (and WWV time signals) before GPS was available. Seeing Nuku Hiva come up on the horizon after 23 days, where and when I predicted using only celestial nav, gave a tremendous and unique feeling of accomplishment.

But for the last many years I've been trying to figure out what to do with my two Davis plastic sextants (from my father, he taught navigation courses) in good useable condition - I have a "real" sextant and don't need these. Advertisements in the local sailing rag got zero response even for a basic giveaway price. Although folks talk about learning celestial, it seems like few are willing or able to spend the time to learn the craft.

So, you all know how to reach me if . . .
I might be interested. I have a 1943 sextant gifted to me by a retired cruiser neighbor, but it needs refurbishing. I am old enough to have done sun sites as a surveyor in the Army to find true direction for artillery, and I always enjoyed that sort of work. If I'm hanging on the hook in the Bahamas I might teach myself celnav. I have Mary Blewitt's book, and have read most of it.
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Old 13-04-2018, 18:44   #173
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Re: Thorny subject: Sextant and GPS era

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Well which Davis sextants have you got and how do you fancy selling them to someone 1/4 of the way around the world for a fair price incl postage? I would actually prefer a plastic sextant due to cost rather than an expensive metal one.

Pete
GPS stands for Grey Plastic Sextant...I had both metal and plastic and they both worked equally well just make sure you don't leave the plastic one in the sun.
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Old 16-06-2018, 08:32   #174
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Re: Thorny subject: Sextant and GPS era

We had a sextant and tables on board, but never actually used them except to practice. For actual navigation we used a gps chart plotter along with paper charts. In actual practice we had more than one hand held gps for backup in case a lightning strike destroyed the chart plotter attached to ship power. Every hour we used gps to get a fix that we entered on the paper chart and we extended a DR plot from that based on known or estimated wind and current. If the gps service was discontinued, we could continue on with dead reckoning and updates from sextant fixes.
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Old 16-06-2018, 08:51   #175
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Re: Thorny subject: Sextant and GPS era

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Hello, last week-end I got unwillingly into a thorny discussion with an other boater about Sextant and GPS.

So anyways this post is not to argue the necessity or not of knowing how to use a Sextant.

What I'm looking for is actual accounts of sailors, getting lost or in trouble because they're GPSs broke down and did not know how to navigate without a sextant.
Actual bleue water sailors.
I have never heard a single story about that.
Losing the GPS "system" as a whole is as unlikely an event as to not be worth thinking about. If that happened because of some natural or man-made disaster, I might not want to come back to shore for a while!

On the other hand, every boat out there is just one lightening strike away from the 19th century. I know of several boats who had ALL their instrumentation and electrical systems destroyed by a near misses. I do not personally know of any boat where that happened offshore.

Granted, in the middle of the ocean, cloud to ground lightening is less common than in someplace like Florida, but it certainly can happen. You can have a handheld gps stored in a metal box onboard that SHOULD survive. Probably. But if you only have electronic charts, what good does knowing your Lat/Lon do you?

I carry paper charts, a mechanical clock, a 30 year almanac and a sextant. Enough to find my way--close enough. I am not an expert at it, but I have done it and it is not hard, just fussy.
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Old 16-06-2018, 11:40   #176
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Re: Thorny subject: Sextant and GPS era

Maybe you have never heard of anyone who was lost at sea after a GPS failure is because.
They did not survive to tell the tale.
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Old 16-06-2018, 13:13   #177
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Re: Thorny subject: Sextant and GPS era

We twice ran across boats at sea, who had lost their gps and did not have much of an idea where they were. But neither was panicking. They both knew if they headed east they would come to a big continent eventually

Back in the early gps days, when we had only one, we lost our gps once (Lightning). But again, no panic, as I had a basic grasp of navigation
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