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Old 04-02-2016, 12:46   #1
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Lightbulb A sextant for the 21st century?

Hello Navigators (and tinkerers)

Here and on other fora I came to realize that there are roughly two kinds of people using sextants:
1 - People who want to be able to have a back-up when all power is down
2 - People who just like maths and old-school stuff
I am in the first category. I even use a slide-rule for the calculations for exactly that reason! Today I was brushing up the "skills and drills" a bit when I had a thought...

There are digital calipers that can measure to a 1/10 of a millimeter accuracy. Just so you don't have to bother with the vernier. So why is this not in use on sextants?
Actually, when you think about it... it should be fairly easy to couple this measurement with a blue-tooth-unit and transmit the measured angle of a sight to a tablet. And since BT goes back and forth, have an app that tells you where to find a certain star, asks you to take a sight, goes on for two extra stars (with a nice star-map) and then simply tells you where you are...
Shouldn't be all that difficult right?

...In for a penny, in for a pound... To make it a bit more robust, one could think about integrating the sextant and a display. So there is a watertight, touch-screen device, with a solar panel on its back for power, all immersed in epoxy and mounted on the body. It lets you select a celestial body of your choice, takes the measurements you took through the good old mirrors, asks some additional info (for example height of sight) and then spits out a position.
The tables can be uploaded (years) in advance via BT and with all the formulas not take up more space than an old floppy disk*. a simple quarts clock (with radio time signal adjustment) for the time. The display is (of course) only in red&black so it shouldn't take that much power at all. Add some magneto compass to help find stars and additional information could be displayed in the eyepiece (more up, more to the left) like a HUD to assist finding stars that are not on your standard repertoire.

So I wonder... why is such a sextant not on the market? These calipers can be bought for next to nothing, add the electronics and you have a reasonable sextant for say $200,- that is easier to use and does what the "modern man" expects. (i.e. take out that "difficult" math ) It surely is cheaper than most new sextants. Shouldn't this be the way forward as a backup to GPS systems and as a way forward in CelNav? Provided of course that it is all water tight. It's not that necessary to have it all too robust, the mirrors will always remain the weak spot of course.
So I ask: what are your thoughts on this little idea of mine?



*for the younger cruisers; a floppy disk is what we used in stead of a memory stick. It looked remarkably like the little square you nowadays press when you want to "save a document"
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Old 04-02-2016, 13:02   #2
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Re: A sextant for the 21st century?

Digital calipers and blue tooth... just after you said something about the reason to do it is you have no power.


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Old 04-02-2016, 13:21   #3
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Re: A sextant for the 21st century?

All that stuff sounds a lot more complex than a spare GPS with a coupla AA batteries.

The reason why such a device doesn't exist is because there's no market.
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Old 04-02-2016, 13:30   #4
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Re: A sextant for the 21st century?

Quote:
Originally Posted by A ursae minor View Post
there are roughly two kinds of people using sextants:
1 - People who want to be able to have a back-up when all power is down
2 - People who just like maths and old-school stuff
//
So I wonder... why is such a sextant not on the market? These calipers can be bought for next to nothing, add the electronics and you have a reasonable sextant for say $200,- that is easier to use and does what the "modern man" expects. (i.e. take out that "difficult" math)
I think you answered your own question

The people who like to use it as a backup will probably not opt for this system cos then they'd need a backup for the backup
The people who just like the math and navigating the "old way" will want to do just that, and you just took out the challenge.

I don't really see who'd buy this - most people will either go for a handheld GPS or an old fashioned sextant. Or both.
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Old 04-02-2016, 13:44   #5
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Re: A sextant for the 21st century?

A backup is no good unless you practice every day.
Easy to perform a miscalculation or wrong lookup in the almanac/tables.
Easy to forget the time variable and keeping track.
Easy to forget the planets and stars
Easy to forget some of the other advanced calculations for finding long by lunar distance if you are giddy and interested.

I think its the other way if you use it at all. Use it every day with a GPS backup. But good luck using it every day since most days are cloudy.

Back to GPS...

Make your own electronic sextant? The reason for using a regular sextant is do you DON'T rely on electronics.
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Old 04-02-2016, 13:58   #6
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pirate Re: A sextant for the 21st century?

In this day and age a sextant as a back up is not needed.. all one needs is a compass and a 'proper' pilot chart..
Anyone with half an education should be able to DR a couple of thousand miles to within 50 miles of their destination if everything crashes..
Its basic geography and simple math...
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Old 04-02-2016, 14:10   #7
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Re: A sextant for the 21st century?

A ursae minor:
You nailed it. I often wondered why we couldn't have a digital sextant, stabilized, and artificial horizion.
I am a navy trained navigator and do shots to keep the skill and as backup. I spent years on boats and ships and except for the ones I owned, almost all suffered a power/engine failure at some time.
Also with the international politics of today, the various GPS systems could be shut down or made inaccurate w/o notice.
A sextant turned horizontally makes a very accurate piloting device. With a 3-armed protractor, I get very close to GPS positions.
I crossed the Pacific before GPS was available, mostly overcast. Navigated w/depth soundings and the rare shot. Also Loran when in range. Set and drift was often 1 knot. Dead reckoning, unknown currents over a couple thousand miles would be much more than 50 miles.
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Old 04-02-2016, 14:24   #8
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Re: A sextant for the 21st century?

Quote:
Originally Posted by boatman61 View Post

Anyone with half an education should be able to DR a couple of thousand miles to within 50 miles of their destination if everything crashes.
50??? Why when I was a kid we used to do it within 5! Kidz these days!

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Old 04-02-2016, 14:36   #9
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Re: A sextant for the 21st century?

Often wondered if a digital camera could be calibrated to read angles accurately.

If so take a few snaps of the Sun and horizon with a smart phone, and let some app do the calcs for you.
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Old 04-02-2016, 14:55   #10
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pirate Re: A sextant for the 21st century?

Quote:
Originally Posted by Lepke View Post
A ursae minor:
You nailed it. I often wondered why we couldn't have a digital sextant, stabilized, and artificial horizion.
I am a navy trained navigator and do shots to keep the skill and as backup. I spent years on boats and ships and except for the ones I owned, almost all suffered a power/engine failure at some time.
Also with the international politics of today, the various GPS systems could be shut down or made inaccurate w/o notice.
A sextant turned horizontally makes a very accurate piloting device. With a 3-armed protractor, I get very close to GPS positions.
I crossed the Pacific before GPS was available, mostly overcast. Navigated w/depth soundings and the rare shot. Also Loran when in range. Set and drift was often 1 knot. Dead reckoning, unknown currents over a couple thousand miles would be much more than 50 miles.
Guess mine was a fluke then.. I was 20 miles of Falmouth after 1100 miles..
I do carry the full World set of Admiralty Small Boat Charts which give a lot of info on winds and currents.. did get nervous thinking I'd missed Lands End so waved down a Coast Guard cutter out on sea trials who gave me my position.. and fresh food.. I was 46 days out of SMX...
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Old 04-02-2016, 15:25   #11
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Re: A sextant for the 21st century?

Quote:
Originally Posted by Snowpetrel View Post
Often wondered if a digital camera could be calibrated to read angles accurately.

If so take a few snaps of the Sun and horizon with a smart phone, and let some app do the calcs for you.
Most tablets and mobile phones these days can measure angles to 0.1 of a degree. Add one to a suitable holder for taking sights and Wallah!


But back to the OP, it's not rocket science to read a vernier scale. I reckon if you're going to keep a sextant as a backup, everything else related to calculating position should be kept manual as well right down to printed out sight tables. Otherwise, what's the point?
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Old 04-02-2016, 15:31   #12
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Re: A sextant for the 21st century?

What's a sextan...Ohhhh yeah, now I remember.

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Old 04-02-2016, 20:09   #13
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Re: A sextant for the 21st century?

Quote:
Originally Posted by boatman61 View Post
Guess mine was a fluke then.. I was 20 miles of Falmouth after 1100 miles..
Ok that was good. Very good.
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Old 04-02-2016, 20:32   #14
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Re: A sextant for the 21st century?

I have a sextant and used to have a programmable calculator with a nav program in it which allowed you to put in the elevation and time only for a number of stars and it would then give you a position, you did not need to identify the stars. Very handy.

I now have three stand alone GPSs, about three of the usb hockey puck types, three or four computers and a couple of tablets, one with an internal GPS, two inverters, and six banks of 12V batteries. If that lot wont look after telling me where I am I'll just heave to at night and eyeball the nav in daylight.

I am not paranoid enough to need to use the sextant these days but it makes a nice nautical theme wall decoration.

I figure that if anyone switches off the GPS system WW3 has started and we are all doomed anyway.
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Old 04-02-2016, 20:43   #15
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Re: A sextant for the 21st century?

So I heard the US Navy was starting to train its officers and navigating seamen on celestial navigation so they could navigate when the GPS satellite system went down (WW III?). If they are doing it then I won't be surprised if they ask the US Congress for funds to develop an electronic version that has all the star charts, tables, calculations, timers, etc. etc. in the on board systems with some pretty fancy stabilized optics. They will have plenty of power on board (or else they have bigger problems than knowing where they are). Then eventually it will be declassified and made available to all the sailing geeks who love this type of new electronic system. Which is pretty much what happened to GPS originally to now. By that time we will have sailing robots which run the boat, navigate, and swab the decks and clean the heads. All we have to do is sit back and sip on our sundowners while the NMs slip away under our keels.
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