21st century sextant?

[macd]

Not intending to fuel any debate about GPS v traditional position-finding, just musing why there is no such thing (so far as I'm aware) as a 'smart' sextant. Can't see any reason why it couldn't incorporate its own timing mechanism, tables etc from which to make its own calculations: in other words, a sort of point and shoot 'find where you are'.

I can certainly see why such a device probably wouldn't be commercially viable, but would make a great technical degree project.

Any thoughts? Any word of attempts to create such a thing?

By way of a PS, I thought I'd Google 'smart sextant' and came up with the Morton Smart Sextant, which seems to be a RNVR award used mainly for navigating around a cocktail party.

 

[prv]

My sextant book mentions exactly the kind of device you envisage, as a new invention just appearing in prototype form (book is from the mid-80s). Supposedly you would tell it what body you're looking at, take the sight (automatically averaging several if you like) and it would read out a line of position.

I guess the arrival of civilian GPS killed off such things.

Pete

 

[Graham_Wright]

Not intending to fuel any debate about GPS v traditional position-finding, just musing why there is no such thing (so far as I'm aware) as a 'smart' sextant. Can't see any reason why it couldn't incorporate its own timing mechanism, tables etc from which to make its own calculations: in other words, a sort of point and shoot 'find where you are'.

I can certainly see why such a device probably wouldn't be commercially viable, but would make a great technical degree project.

Any thoughts? Any word of attempts to create such a thing?

By way of a PS, I thought I'd Google 'smart sextant' and came up with the Morton Smart Sextant, which seems to be a RNVR award used mainly for navigating around a cocktail party.

………complete with a pendulum operated angle decoder. Seems obvious to me so why hasn't it happened?

 

[vyv_cox]

………complete with a pendulum operated angle decoder. Seems obvious to me so why hasn't it happened?

Could perhaps be built for £2000?

 

[KellysEye]

>I guess the arrival of civilian GPS killed off such things.

You are right, a smart sextant is a good idea but unfortunately won't happen. We carried a sextant for fun trying to get as close to the GPS position as possible, you need things to do on long passages.

 

[pcatterall]

I think the 'smart' sextant may be a step to far. For the sighting purposes simplicity and robust construction are important. However there seem to be some clever 'dedicated calculators' ( one by Texas instruments) which will take your sights and do the calculations for you. This means that you can take loads of sights to improve accuracy. Tables and the ability to use are still an important back up.

 

[prv]

Here's a quick and dirty photo of the relevant page in the book:

Pete

 

[prv]

I think the 'smart' sextant may be a step to far. For the sighting purposes simplicity and robust construction are important. However there seem to be some clever 'dedicated calculators' ( one by Texas instruments) which will take your sights and do the calculations for you. This means that you can take loads of sights to improve accuracy.

The thing about a fully-integrated system is that recording a sight is as simple as pressing a button. That instantly transfers the time and angle into the computer, and you're free to take another sight a second later. Being able to trivially average a dozen elevations from a dozen quick beeps must make the overall accuracy much better. If you're writing down each figure and looking at a stopwatch before manually transferring the data to a separate computer, you're not going to take so many sights.

Tables and the ability to use are still an important back up.

I think it's this combined with GPS that really killed off the smart sextant. If GPS had never been invented, I'm sure we'd all be using fourth-generation Celnavs by now. This would be our day to day navigation tool and we'd accept every bell and whistle imaginable just like people now do with plotters. However, GPS has relegated celestial nav to either retro hobby or last-ditch backup, and for both of those purposes you want simple and traditional rather than high-tech.

Pete

 

[macd]

………complete with a pendulum operated angle decoder. Seems obvious to me so why hasn't it happened?

Digital 'spirit' levels have been around for years and continue to get cheaper. Most probably lack the accuracy required for a sextant (for fun, I've used mine to find latitude from the Pole Star: accuracy about +/- 30miles), but that can probably be overcome at a price.

I quite agree that the advent of GPS must have rendered such a thing untenable on price, hence my comment on commercial viability, but still a great project for some aspiring tech student, maybe?

 

[Twister_Ken]

I was involved with a 'genius inventor' who was developing a digital sextant - must have been mid-80's – using a strain gauge to measure angular displacement and to feed readings to a calculation chip linked to an electronic almanac. Whilst he was struggling to get it right, and bring the manufacturing cost down, GPS kept getting cheaper. Eventually he realised (with some prompting!) that he was developing something with a potential market in the low hundreds, not the high thousands, and went away to invent something else.

 

[prv]

Digital 'spirit' levels have been around for years and continue to get cheaper.

Would such a thing be useable on a pitching boat? We don't use plumb-lines (the mechanical equivalent) to get verticality on a traditional sextant, we use the horizon for a source of (almost, correctible) horizontal instead. The electronic sextant shown above (and another over the page) also measured angle between star and horizon, not star and pendulum/level.

Pete

 

[NUTMEG]

I am sure I saw an iPhone app that did what you are discussing. Will have a look to see if I can find it.

It used the accelerometer to calculate angle and I think there was a calculator and almanac built in.

 

[concentrik]

Would such a thing be useable on a pitching boat? We don't use plumb-lines (the mechanical equivalent) to get verticality on a traditional sextant, we use the horizon for a source of (almost, correctible) horizontal instead. The electronic sextant shown above (and another over the page) also measured angle between star and horizon, not star and pendulum/level.

Pete

Maybe the whole idea of resolving 'live' angles is redundant? A series of still photographs which capture the sun and horizon could be analysed in software, averaged and calculations applied. I suppose that's cheating. It's probably an impractical idea, as I know nothing about sunsights (but have a strange inclination - Ha! - to learn)

 

[mrming]

There are a few different sextant apps in the App Store - there's no reviews on any of them so it's difficult to tell if they're any good, but this one has a free version: https://itunes.apple.com/gb/app/solar-sextant-free/id518520318?mt=8

 

[maxi77]

All submarines used to have and possibly still do have a periscope sextant which had many of the features required of the smart sextant. It was intended to be used dived when the operator could not compensate for boat movement ad required the operator to keep the object being measured between 2 lines using a thumb switch for some 2 minutes, by measuring one sixtieth of the angle every 2 seconds and adding them it gave an averaged measurement of the altitude. This was all clockwork stuff so could be easily made electronic these days, digital sight computation has been with us for years, so if there was a real market it could all be done, but as suggested GPS/GLONASS has ensured the market is in fact minute

 

[oldbilbo]

All submarines used to have and possibly still do have a periscope sextant which had many of the features required of the smart sextant. It was intended to be used dived when the operator could not compensate for boat movement ad required the operator to keep the object being measured between 2 lines using a thumb switch for some 2 minutes, by measuring one sixtieth of the angle every 2 seconds and adding them it gave an averaged measurement of the altitude. This was all clockwork stuff so could be easily made electronic these days, digital sight computation has been with us for years....

That's not far removed from the astro-navigation system installed/used in 70s V-Force Vulcans, etc. using 'periscopic sextants' to find the Soviet Union. Every - and I mean every - navigator in the Force could take an aircraft down a 2-mile wide corridor in the sky after 1500nm of high-level transit. The best of them, with a lot of tweaking, could be relied on to demonstrate 'an order of magnitude better' and arrive well within 10 seconds of pre-planned time.

The 'septics' couldn't believe what our guys could accomplish, by dint of practice, practice, practice..... but we regularly carried off NATO Bombing Competitions that the best of the USAF couldn't - despite $millions being thrown annually at the event.

No, I have no idea how good the Russkies would have been. They weren't invited....

 

[maxi77]

That's not far removed from the astro-navigation system installed/used in 70s V-Force Vulcans, etc. using 'periscopic sextants' to find the Soviet Union. Every - and I mean every - navigator in the Force could take an aircraft down a 2-mile wide corridor in the sky after 1500nm of high-level transit. The best of them, with a lot of tweaking, could be relied on to demonstrate 'an order of magnitude better' and arrive well within 10 seconds of pre-planned time.

The 'septics' couldn't believe what our guys could accomplish, by dint of practice, practice, practice..... but we regularly carried off NATO Bombing Competitions that the best of the USAF couldn't - despite $millions being thrown annually at the event.

No, I have no idea how good the Russkies would have been. They weren't invited....

Just goesto show the Crabs were good at copying, boats were using them in the Barents sea long before the 70s

 

[Malabar]

A sextant with a night capability i.e. with an image intensifier/low light is a great advance. Take star sights at any time in the night rather than at twilight. Not difficult to provide. The other technical improvement would be a stabilised horizon, again very achievable technically and probably at reasonable cost.