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Old 06-06-2010, 21:03   #1
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For All Those Who Only Use Electronic Navigation...

For years we have had a relatively quiet time out there in space. So much so that I believe the recent cold climate we have had was the result of less solar radiation. Well- the sun is back! And it is ready to cause havoc. Just something to be aware of when you decide to go offshore...
As the Sun Awakens, NASA Keeps a Wary Eye on Space Weather - NASA Science
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Old 06-06-2010, 21:16   #2
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oopS! Back to my trusty sextant
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Old 06-06-2010, 21:17   #3
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I'm three weeks into a cruise, and just seen two days of sun, and below normal temperatures. I hope that you are correct!
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Old 06-06-2010, 21:46   #4
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I spent five years navigating in the Arabian desert using compass and sextant before I ever went sailing. I used a World War II aircraft bubble sextant for desert navigation. I would take noon sites, and evening star sites usually getting within a couple of miles of my GPS position. It was easy to do and fun. It was also great practice.

I would not be afraid to repeat my circumnavigation using a sextant and compass, but I would probably drop a couple of destinations off my list of places that I would stop. The Tuamoto Archipelago of French Polynesia is a non-forgiving place, and a mistake can easily coast you the loss of your yacht or ever your life. There are lots of currents and low lying islands that you can't see until you are only a mile offshore where you just see the palm trees without any land until you are too close to shore for comfort. It's definitely unsafe to operate in those locations at night and without knowing exactly where you are.

I would do a lot more standing off farther from land when I got near to my destinations. I would also put a permanent crows nest on the first set of spreaders to increase the range of vision in marginal navigational areas.

It sounds like fun to me.
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Old 06-06-2010, 21:59   #5
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Ye Gods. Four posts into a sextant thread and nobody has yet said that electronics never fail, batteries never flatten, lightening never strikes, the GPS will run for ever, or that dead reckonng will get you to the Marquesas!

What on earth is this forum coming to?
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Old 06-06-2010, 21:59   #6
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I'm three weeks into a cruise, and just seen two days of sun, and below normal temperatures. I hope that you are correct!
Amen Brother!

Week and a half of straight rain and cloud cover here...Bring it on...I'll take my solar flair chances...electronics only for this kid.
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Old 06-06-2010, 22:22   #7
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Some things you only need one of, and some things you need backup for.
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Old 06-06-2010, 22:24   #8
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Don't use a metal sextant in a thunderstorm, because if it gets struck by lightning, it will melt, warp, or otherwise malfunction.
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Old 06-06-2010, 22:38   #9
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Don't use a metal sextant in a thunderstorm, because if it gets struck by lightning, it will melt, warp, or otherwise malfunction.

The sextant or the operator?
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Old 08-06-2010, 03:34   #10
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Increased solar activity does not really mean that the weather will be warmer. The two systems don't couple in a simple way. During the peaks of the solar cycle (last one was 2000) ionospheric effects can interfere with HF comms. Solar flares and coronal mass ejections are associated with peaks but may happen at any time. These cause enormous electrical currents to flow around the magnetosphere which can be a bit tricky. Inductive effects have caused power outages and damaged satellites. Of course modern satellites are designed with this in mind so it would take an eye wateringly large CME to take out the GPS chain. This is possible but, imho, if you are seriously worried about it then what with asteroids, super volcanoes, global warming and pandemics then rather than getting a sextant you should possibly just stay in bed.
btw I like sextants
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Old 08-06-2010, 04:38   #11
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Quote:
Originally Posted by maxingout View Post
Don't use a metal sextant in a thunderstorm, .
A sun shower?


LOL


No matter how much sun spot activity there is it will still make GPS's far more accurate than Daves "usually getting within a couple of miles of my GPS position"

And as for the hoary old argument about only having one battery and only 1 GPS on board a boat, I can safely tell you Slocumb had only one set of charts and the goat ate them and put him in peril!!!

So we have no paper, no goats and more than one battery and more than 1 GPS. <<Presto>> we also have more than one fix per day!! Except for thunderstorms where you have NO fixes for maybe a week.
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Old 08-06-2010, 05:47   #12
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Hmm. A sextant will give you an estimated position twice a day. Definitely better than nothing. We log a GPS fix every hour and at every course change. We could tolerate loss of electronics and GPS for 12 hours, depending on where we were at the time. I wonder if we'd get GPS back in that time? Shrug... When I plan on being away from a landing for more than a week, I'll have to re-evaluate.
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Old 08-06-2010, 05:55   #13
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Hey, hang on, I just had a thought.... (don't laugh)... the folks that use a metal-shine-it-at-the-sun-doodad do you use a calculator or computer to work out the maths??????????????????

Or a pen and paper?

Admit it.


So a power outage will stuff the pro-sexytant people just as much as the mythical problems with a single gps...
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Old 08-06-2010, 09:10   #14
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How does it affect a slide rule LOL...
Now I like my GPS as much as anyone. But we will see how sensitive they are to lots of sunspots....So yes I have a sextant on board, and I am learning to use it- without electronics. But I am just an old fogy Mark.
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Old 08-06-2010, 09:25   #15
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In the early 90s, when the number of GPS satellites were less than the fingers on one hand, we'd regularly get hours of no satellite coverage. We still managed to find the Virgin Islands after leaving Florida.

There was a news report some time ago about GPS problems with the military but civilian use was fine.

One of the reasons for plotting on a chart is that you know where you were, when, and what your course was. You can use DR/WAG or whatever you like to plan the next leg.

Learning to use a sextant isn't hard, there are programs and look-up tables that can make the reduction easier and you'd be surprised how accurate it can be considering the ease of errors. And sextants can do more than determine your lat/long.
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