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Old 06-02-2016, 15:33   #61
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A sextant for the 21st century?

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Originally Posted by A ursae minor View Post
Hey everyone!

Please do understand my initial post. I don't want to start a discussion on what backup for GPS is best and why. There are way to many on those as it is. My intention is only to start a discussion on the concept of a digital sextant and to what extent it would give 'added value' over the existing (analogue) sextants. Perhaps I should have mentioned that in my initial post (my bad, sorry!)

The lightning problem is actually the only real danger to a device like I suggested. As it is for any electronics. Sometimes failures may occur months or even years after being struck. So, even if your precious (backup) GPS might seem to have survived, it well might collapse 3 months later. When you are out on the big-big-lake, approximately eight notevencloses south of the next radio contact.

I would have the same problem with the digital sextant. Although it is of course well possible to engineer it in such a fashion that it is also possible to use it in the analogue mode with the good old pen and paper. In which case it is a backup of a backup
(shouldn't lose the backup, cause I would lose its backup as well )

Anyway. Apart from anyone's favorite backup for GPS, what are your ideas on the proposed new cousin of the digital calipers?

I think I got the answer you are looking for. I went to a boat show and asked the vendor why I would want a $2000 sextant vs the Celestaire. He said, and I paraphrase " ... For small boats such as my 40 ft there is no advantage. No matter how good the instrument, all the bouncing around puts a limit on sighting accuracy. The more expensive sextant are designed for use on more stable platforms. ".

I have a set of digital calipers and they are a pain. The numbers they give are too precise. Reminds me of a story that we geologist used to tell.

An interviewer was evaluating a geologist, geophysicist and an an engineer for a job. He asked the engineer "how much is 2 +2".
The engineer whipped out his calculator and pronounced it to be 4.00000.

He then asked the geologist the same question. That worthy fellow concentrated mightily and pronounced the answer was between 3 & 5.

Finally, the geophysicist. He got up, checked the hallway, closed the door and whispered "What do you want it to be?"

Thank you for your patience, I can be found here most Saturday evenings, please tip your waiters.

There is actually a point here regarding precision and accuracy

A digital sextant maybe more precise but on a small boat, I doubt you would find it any more accurate.

Rich


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Old 06-02-2016, 15:43   #62
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Re: A sextant for the 21st century?

For the OP, I don't think some sort of automated sextant is going to be easy to market, unless it's cheaper than any alternatives and has a viable non electric mode.

Most celestial enthusiasts are happy to play with old tech and even enjoy the challenge. The gps set really just want a usable backup, but don't expect to actually have to use it, so won't pay big dollars for something. and even then I think there are plenty of people crossing oceans at the moment with no sextant aboard, just GPS.

At the moment a very nice secondhand metal sextant seems to be worth about $500 or so, far below its true replacement cost. And the Davis mk3 and ebbco sextants are nearer the $50 mark new and are perfectly fine for casual and emergency use.

Just a set of plain digital calipers is $50-100, without waterproofing or Bluetooth. I just don't see how something could be made that's going to really be able to be sold at a marketable price, when the "need" isn't there.

The only way I can see the technology working to improve celestial is using an existing mobile phone as a sextant somehow. Then you don't have any additional hardware to buy. I'd happily pay $20 for an app that would let my phone work as a sextant, if even just for the curiosity value.
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Old 07-02-2016, 05:59   #63
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Re: A sextant for the 21st century?

I really don't want to be condescending, but I am quite baffled at the amount of posts that are referring to a smart-phone (including my own scribbles).
These things are extremely versatile these days, true, but the battery life is hopeless. I have to recharge mine nearly every day. It is almost like keeping a bloody tamagotchi alive

Anyway, I came to understand that my idea was not entirely the epiphany I initially though it was
Although I still have a feeling that the sextant as an instrument is not necessarily crystallized out into perfection just yet. It should be possible to enhance it somehow, although (apparently) it might take a brighter mind than mine.

By the way, the book on emergency navigation as suggested above is a very well written and interesting book. I too would warmly recommend it. The weather forecasting sheet is now on my wishlist, thank you for suggesting it SaltyMonkey (and no, I will not dump my sextant )!
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Old 08-02-2016, 09:26   #64
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Re: A sextant for the 21st century?

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All that's needed is for a large solar flare to occur pointed directly at earth, will knock out all our GPS satellites for several months not to mention major damage to power lines taking out thousands of cities power supply. You don't need WWIII. Lack of land based power will also most likely mean there will not be any land based radio signals to lock onto, that is the reason the US Navy is reintroducing basic Celestial Nav training for their deck officers.
Well, given that a Carrington class solar event happens about once every 150 years, and the last one was in 1859 . . . . .

The last one didn't just create havoc with the telegraph system, it also knocked out compasses on ships.

I wonder how such things as Smart Meters, WiFi, Internet of Things, etc., will cope?

Let alone land line phones, mobile phones . . . . . .
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Old 08-02-2016, 09:37   #65
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Re: A sextant for the 21st century?

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Well, given that a Carrington class solar event happens about once every 150 years, and the last one was in 1859 . . . . .



The last one didn't just create havoc with the telegraph system, it also knocked out compasses on ships.



I wonder how such things as Smart Meters, WiFi, Internet of Things, etc., will cope?



Let alone land line phones, mobile phones . . . . . .

Carrington class events are 500-yr events. Even so there a couple a century that are less powerful. The 1989 event knocked out power to a big chunk of Quebec.


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Old 08-02-2016, 09:45   #66
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Re: A sextant for the 21st century?

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Carrington class events are 500-yr events. Even so there a couple a century that are less powerful. The 1989 event knocked out power to a big chunk of Quebec.


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Not according to a meeting of space experts in 2013, who attended a conference to discuss precisely this matter.

1989 was no Carrington Event. Definitely no cigar.
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Old 08-02-2016, 10:16   #67
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Re: A sextant for the 21st century?

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Not according to a meeting of space experts in 2013, who attended a conference to discuss precisely this matter.



1989 was no Carrington Event. Definitely no cigar.

Correct, 1989 was not a Carrington level event and it still knocked out power.

Do you have a URL for the 2013 report?


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Old 08-02-2016, 11:05   #68
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Re: A sextant for the 21st century?

I think one must remember that such events (scale-busting EMP or solar flares) are not being ignored out of stupidity. But rather, they are in the "nightmare closet" of every emergency planner, simply because of the economics of the problem.


Bear in mind that no one was willing to pay for lifeboats, building them or making space to stow them, until after Titanic. And no one was willing to put up with lifeboat drills, arguably before the first dinner seating and possibly before even leaving harbor, even after Costa Concordia. How soon we forget?


In the 1960's when US Civil Defense policy including teaching school children to "duck and cover" the planners knew very well that the average Soviet bomb, even if it landed 20 miles off target, would totally obliterate steel and masonry buildings. They also knew the public might panic at hearing that, so instead they told everyone to duck under their desks to take cover from flying glass. That's called psyops, psychological operations, and it was done after the World Trade came down too.


In NYC, there are about 1/4 million elderly and infirm residents in tower housing in the Rockaways. Evacuation plan? Well, about 90% didn't self-evacuate when ordered to before TS Sandy. Emergency management plan? None, for the simple reason that if you booked every ambulance and medical transport vehicle in a six-state zone, that still wouldn't be enough to evacuate that many people, even if they got themselves to the street level. So you hope that if "the big one" happens, they'll die quickly and painlessly, because there's nothing else you can do.

There are always limits to resources. If the national or international power grids go down, odds are that utility transformers will have burned out, along with miles of cabling. There are almost no spares for those transformers, because they are custom built and can take six months to replace. No one is willing to pay for making up spares, let alone storing them. No one.


And in the US, when a California power substation was literally attacked and shot up by unknown parties in the night (2013?) it took over a year for the news to leak out, and about that long to replace the equipment. Consensus after the reports? No spares, no capability to provide them faster, no funding to fix that.


Which brings us back to boats after a major "EMP" or solar event. Unless you have an old diesel engine, with a purely mechanical fuel pump (no turbos, no fancy control systems, no electric high-pressure pumps) and a good way of hand starting...you may need more than a backup nav system. If the grid goes down, road and rail transport also goes down. Food distribution goes down. Spares? There might not be any, until someone figures out how to restart the foundries that cast the metal that gets made into the replacements.


And the emergency planners, like most of the rest of us, ignore tis scenario because realistically, unless you are willing to commit a huge chunk of your personal time and money to the problem, there's no much you really can do to address it.


On the bright side, if you've got sails, you just might get lucky enough to have the government hire you and your vessel for shore patrol. They might just keep you fed.
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Old 08-02-2016, 16:45   #69
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Re: A sextant for the 21st century?

Drift..... A pocket sized device to lock in angle and GMT at the push of a button sounds like something I would add to my ditch bag for under $50.00. No need for BT or the rest. Could be done with minimal power requirements, and weatherproofed. Synergy used to be just a word thrown around at motivational meetings to me. Lately I have seen some great examples. Crowd sourcing is an evolutionary leap. Take a look at the Open Plotter thread for an example.
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Old 08-02-2016, 18:42   #70
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Re: A sextant for the 21st century?

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Drift..... A pocket sized device to lock in angle and GMT at the push of a button sounds like something I would add to my ditch bag for under $50.00. No need for BT or the rest. Could be done with minimal power requirements, and weatherproofed. Synergy used to be just a word thrown around at motivational meetings to me. Lately I have seen some great examples. Crowd sourcing is an evolutionary leap. Take a look at the Open Plotter thread for an example.
Steve Callahan was able to establish his latitude with three pencils held together with elastic and a compass rose, and his longitude with dead reckoning.
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Old 08-02-2016, 18:57   #71
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Re: A sextant for the 21st century?

Seems to me is that if there was anything I wanted integrated into a sextant, it'd be a stopwatch. If your time is off, it doesn't much matter how accurate your angle.
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Old 08-02-2016, 19:13   #72
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Re: A sextant for the 21st century?

Stopwatch? Velcro. Makes it real easy to go "click" at the moment you've made a sight. And if you use the lap timing function, so you only have to note the offset from "true" time, you don't even need a stopwatch that's deadly accurate.
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Old 08-02-2016, 19:30   #73
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Re: A sextant for the 21st century?

Something like a bris sextant attached to the top of a waterproof smartphone. Push the button when the sun touches the horizon, and the computer can do the rest, it could probably even tell you when the next "sight" is due and sound an alarm. Add a solar panel and a faraday cage, plus some Manuel backup tables and you have a pretty simple to use system, that should be pretty cheap.

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Old 11-02-2016, 11:45   #74
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Re: A sextant for the 21st century?

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The people who like to use it as a backup will probably not opt for this system cos then they'd need a (manual) backup for the (electronic) 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.
Exactly.

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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 don't do lunars, so have no opinion on that. But with respect to bog standard sight reduction by tables, I disagree that daily practice is necessary to remain reasonably proficient.

I do no practice between voyages, and as a result am 'rusty' and require reference to cheat sheets or books for the first couple of days (Tim Bartlett’s RYA Astro Navigation Handbook has good worked examples and is easy to follow). But proficiency then returns very quickly.

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[G]ood luck using it every day, since most days are cloudy.
I don't know where you sail, but in my own experience a day of constant overcast with no opportunities for at least two or three quick sun sights is the exception rather than the norm. Not to say that I've never had three or four days of complete fog, but that has been atypical for ocean sailing (again, in my experience. I don't sail the North Atlantic in the winter season ... but few people do).

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It's spelled "Voila".
+1. The amount of illiteracy on daily display through the Internet is embarrassing.

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Seems to me is that if there was anything I wanted integrated into a sextant, it'd be a stopwatch. If your time is off, it doesn't much matter how accurate your angle.
While I do own a nice mechanical stopwatch with flyback function, I don't use it. It's easier just to quickly glance at the seconds indicated on my cheap digital wristwatch: which keeps time at least as well as most mechanical chronometers.
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Old 11-02-2016, 13:27   #75
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Re: A sextant for the 21st century?

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While I do own a nice mechanical stopwatch with flyback function, I don't use it. It's easier just to quickly glance at the seconds indicated on my cheap digital wristwatch: which keeps time at least as well as most mechanical chronometers.
You mean that fancy Poljot marine chronometer I paid way too much money for, back when, wasn't worth the money?
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