A sextant for the 21st century?

[IRG]

Wallah? Is that a navigational term?

Originally Posted by Reefmagnet

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?

[John_Trusty]

Originally Posted by IRG

Wallah? Is that a navigational term?

Can't be a celestial navigation term unless it has an obscure set of initials -- W(l)?

I'm picking this celestial stuff up self-study - I'm in OP's second category of interested in the maths, but don't imagine I'll ever actually need it. I appreciate the comments about never needing it (GPS, terrorism, etc), but then again I'll bet none of you would expect to ever actually need to use a bucket to steer your boat after your rudder left, and yet ...

Anyhow, the US Navy (and others) did develop fantastic programs to aid in celestial navigation -- From American Practical Navigator (Bowditch) chapter 20 https://en.wikisource.org/wiki/The_A...ical_Navigator :
U.S. Naval navigators have access to a program called STELLA (System To Estimate Latitude and Longitude Astronomically; do not confuse with a commercial astronomy program with the same name). STELLA was developed by the Astronomical Applications Department of the U.S. Naval Observatory based on a Navy requirement. The algorithms used in STELLA provide an accuracy of one arc-second on the Earth’s surface, a distance of about 30 meters. While this accuracy is far better than can be obtained using a sextant, it does support possible naval needs for automated navigation systems based on celestial objects. These algorithms take into account the oblateness of the Earth, movement of the vessel during sight-taking, and other factors not fully addressed by traditional methods.

STELLA can perform almanac functions, position updating/ DR estimations, celestial body rise/set/transit calculations, compass error calculations, sight planning, and sight reduction.

[Hoosiersailor]

Originally Posted by hellosailor

maggied-
If you didn't mind the reliance on GPS, you could use the Google Sky Map feature, an app for Androids that lets you point your phone at the sky and then identifies everything you see. A little added programming and you should be able to get the phone to tell you where you are, working backwards from optical recognition on the sky view, without the GPS.

I'm not sure I understand. You have GPS in the phone to tell you where you are so Google Sky map can identify the celestial bodies in the sky to tell you where you are?? Google Sky map has to know where you are to tell you what's in the sky around you.

[Reefmagnet]

Originally Posted by IRG

Wallah? Is that a navigational term?

It's what magician's say when they pull a rabbit out of a hat :-)

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[barnakiel]

Actually, I think I have seen at least one sextant with digital read-out.

I do not want one because I find and average alloy sextant joy to use and nearly un-breakable.

I think a better toy would be a sextant-smatphone combo - you sight the sun, press the button, the toy calculates your horizon and altitude from the smartphone's g sensors. COOOL, NO????

There are air bubble level Apps on Play. All you need to do is to take your sight along the long side of your smartphone ...

b.

[Martkimwat]

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.

[Snowpetrel]

Originally Posted by SaltyMonkey

How about a Kamel?

Who needs a piece of &@#(&$@ sextant when you can have a string with 57 knots?

The History of the Sextant

ha, got within thirty miles of my position once with a bit of string and a plastic ruler. These thing work, not maybe as well as boatmans DR but good for those longer 5000 mile passages.

Maybe a digital micrometer in a backstaff or something as a cheapo version

Originally Posted by woodguy

I've wondered the same thing especially considering the density of pixels in cameras these days, measuring angles should be quite precise,

I tried to take a few pics of the Sun. Far too bright need some sort of good filter, a pair of sunnies held over the lens doesn't cut it!

The Bris sextant is a great bit of kit, very clever and lightweight.

[vtomanov]

there should be a app for ios or android

[Reefmagnet]

Originally Posted by Snowpetrel

ha, got within thirty miles of my position once with a bit of string and a plastic ruler. These thing work, not maybe as well as boatmans DR but good for those longer 5000 mile passages.

Maybe a digital micrometer in a backstaff or something as a cheapo version






I tried to take a few pics of the Sun. Far too bright need some sort of good filter, a pair of sunnies held over the lens doesn't cut it!

The Bris sextant is a great bit of kit, very clever and lightweight.

[Snowpetrel]

Ha , yes got to dig out my welding helmet next :thumbup:

[Adelie]

Originally Posted by Lepke

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.

Digital sextants would suffer from two problems:
A. Cost
B. If it's a lightning strike that does in you electronics, it will do in you sextant too.


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[Adelie]

Originally Posted by Snowpetrel

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.

Yes they can. There's a whole long discussion of various aspects of this on the NavList forum I'm also part of. The bit trick is prevail rating the camera so you know how many pixels per minute of arc. In use the photo is exported to Paint or any thing that will give you x,y coordinates in the photo.


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[captlloyd]

Originally Posted by hamburking

I think I'm in the minority, but I think a digital blue tooth sextant is a great idea. It combines the power of computing with the raw data of the stars...a great application of hardware and software.

I have to wonder how reliable the GPS satellite system would be in case of a terror attack or war. Although there are many satellites, they work in concert. Any error would cause havoc with so many devices. I wonder if this is a possibility and what sort of reliability the system really has? Attack on the system could be via "hacker" into the system, or a more conventional physical attack on the satellites themselves.

Take a picture of the sky (stars) and get your position....that would be awesome.

No, you are not alone. I think the OP has some good ideas.

[Adelie]

Originally Posted by Snowpetrel

. . . I tried to take a few pics of the Sun. Far too bright need some sort of good filter, a pair of sunnies held over the lens doesn't cut it!

Welding shade from a welding supply shop, shade 11 or 12.


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[Olddave]

Originally Posted by Snowpetrel

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.

Snowpetrel, that is clever. I want one.