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El Pinguino · 11-10-2022, 06:29

Quote:

Originally Posted by Benz

^^I'm not getting the same denigration-of-apps vibe that you are; but I do see that some value celestial nav as an electronics-free method of navigating, as much as is possible in these days when wind-up chronometers are expensive antiques and can't be easily serviced.
While I see no shame in using spreadsheets or apps to reduce a sight, I find doing the entire process on paper extremely satisfying. And since I usually draw plotting sheets and keep a running fix on those, of which my celestial LOPS are just a part, using an app would only remove a small portion of the pencilwork and break up my rhythm.
You mention a chartplotter, but surely no one is trying to plot celestial LOPs on a plotter? How is that even done? It would take me longer to input a lat/long derived from my plotting sheet into a chartplotter (which I don't have on my boat) than to simply plot it on my paper chart. Do chartplotters have an azimuth/intercept function?

Easy peasy. Knocked this up on OPCN while waiting for the kettle to boil.
First leg is my track, second leg from my DR is the intercept, p/l laid off at right angles, followed by run from ITP to noon. Latitude derived from Mer Alt laid off as a new route. N/N posn lifted off from where they intersect. Just the same as I would do it on paper.
Back to my coffee which is getting cold.

Icarus · 11-10-2022, 17:14

Quote:

Originally Posted by Idaho

Is there an android app where you input the observed sextant angle and the time, then the app outputs the lat/long?

To calculate the solution, it needs no Internet, no cell tower, no GPS sats. Just the app, the sextant, and the time.

There are hand held nav computers on the market.
TAMAYA is a good one..About 1500$
Makes taking sights easy.

Icarus · 11-10-2022, 17:24

Quote:

Originally Posted by ItDepends

Unless you have a particular type of paranoia, the failure of the satellites is not the issue. Failure of electronics aboard from a lightening strick most certainly IS.

Every sailboat on the ocean is one lightening strike away from the 19th century. If you were 1000 NM from land at that point what would YOU do???

Been there...lost the GPS after a near lightening strike on my way to New Caledonia...
That was before the days when one could buy a GPS for 200$.
Saying that, a 3 way position line position can be very accurate.
Even a simple noon sight Lat can be very useful.

wholybee · 11-10-2022, 17:41

Quote:

Originally Posted by Idaho

Thank you, everyone.

I learned celestial navigation in 1983, then sailed as crew from Panama to Noumea on a boat with only a shortwave receiver for the time signal and a sextant. No fancy Satnav or LORAN.

We typically did noon sights for position. Strangely, we arrived to every island we planned to visit without difficulty locating them.

Now I am making ready for another Pacific crossing, I bought a book to relearn the math, and my crew noticed my sextant and now want to learn how to use it.

I showed them how to shoot the sun at noon, but teaching them the math is a bit daunting. I told them there is an app for that in this more modern age.

So now I am looking for that app.

My suggesting, given your goal, is to buy the workforms for 229 or 249 whatever tables you are using. The back of the book has example sights filled out, along with instructions. It isn't a substitute for a course, but given you have done it before, and that the forms are well laid out and guided with instructions, you should be able to re-learn and teach someone else. You won't have any idea why or how it works, but you will be able to find your location.

https://www.celestaire.com/product/d...-ho-249-vol-1/

The few apps I have looked at, I can't recommend. They are very pretty, plot nice lines and all, and will tell you where you are. But don't do anything for learning, and since they are on a phone with a GPS, wouldn't every be used for navigation, only a toy.

Benz · 12-10-2022, 03:27

Quote:

Originally Posted by El Pinguino

Easy peasy. Knocked this up on OPCN while waiting for the kettle to boil.
First leg is my track, second leg from my DR is the intercept, p/l laid off at right angles, followed by run from ITP to noon. Latitude derived from Mer Alt laid off as a new route. N/N posn lifted off from where they intersect. Just the same as I would do it on paper.
Back to my coffee which is getting cold.

Interesting. Does it take longer than it would on paper? I don't use chartplotters usually, but that's a neat trick.

El Pinguino · 12-10-2022, 05:34

Quote:

Originally Posted by Benz

Interesting. Does it take longer than it would on paper? I don't use chartplotters usually, but that's a neat trick.

I put my noon position on oPCN each day when on passage so that I have an electronic record of the voyage. I don't think plotting P/Ls in this way would take any longer than plotting on paper.

When I first went to sea we had to do everything in our sight books - no plotting sheets. In latter years I was using the big US plotting sheets that you could - depending on how fast you were going - get up to a week's work on from one side to the other.

Sailor Sailor · 12-10-2022, 06:41

Quote:

Originally Posted by wholybee

My suggesting, given your goal, is to buy the workforms for 229 or 249 whatever tables you are using. The back of the book has example sights filled out, along with instructions. It isn't a substitute for a course, but given you have done it before, and that the forms are well laid out and guided with instructions, you should be able to re-learn and teach someone else. You won't have any idea why or how it works, but you will be able to find your location...

I second the recommendation of the Davis 249 worksheets with comprehensive instructions inside the front cover, and would also recommend the Weems & Plath plotting sheets.

ClarkW · 12-10-2022, 17:59

Quote:

Originally Posted by Idaho

Is there an android app where you input the observed sextant angle and the time, then the app outputs the lat/long?

To calculate the solution, it needs no Internet, no cell tower, no GPS sats. Just the app, the sextant, and the time.

I programmed some site reduction routines along with other related useful routines that will run on most capable web browsers including those on an Ipad or an Android. Although you will need internet access to access and download them, you can do a "Save As" or use wget to save the pages to almost any device or computer. You can then load and run them in your browser offline. (Look ma, no new devices to buy, no new software to buy!) This is because they are written in java script language which runs in almost all browsers in the local machine. Do view source to see the calculations. Visit:

The Navigation Page

The 5th link in this page provides some documentation on the inputs and outputs with links to the sight reduction calculators. Or go direct to:

USPS Sight Reduction Form SR 96a Help Page

You will need the current almanac because the tables are too big to store and change from year to year. The SR96 is a form used in the US Power Squadron navigation class for reducing sights. The newest calculator does all the bodies. The calculations for stars are designed to round and exactly match the USPS method. Some of the other bodies do a closest lookup in internal tables rather than interpolating the entries as required in the USPS method. Nevertheless, the answers should be very close to the official method and general use. YMMV. I suggest reviewing or testing the code and double checking it against other position finding sources especially for entries south of the equator.

Clark

billdomb · 13-10-2022, 19:05

Realize this doesn't answer your question, but is somewhat related.

Every 3 square meters on the entire globe has been identified by three randomly selected words.

You can find me at mascot.widget.hours or maybe explorer.ballots.tech

Find yours at what3words.com

a whole Ted talk: https://www.ted.com/talks/chris_shel...place_on_earth

Uh, it takes 57 billion 3-meter squares to do it.
But it only takes 40K words to name them.

Also in a bunch of different languages.

GrowleyMonster · 13-10-2022, 20:04

Quote:

Originally Posted by billdomb

Realize this doesn't answer your question, but is somewhat related.

Every 3 square meters on the entire globe has been identified by three randomly selected words.

You can find me at mascot.widget.hours or maybe explorer.ballots.tech

Find yours at what3words.com

a whole Ted talk: https://www.ted.com/talks/chris_shel...place_on_earth

Uh, it takes 57 billion 3-meter squares to do it.
But it only takes 40K words to name them.

Also in a bunch of different languages.

That should simplify navigation. You only need to remember two words to make a perfect landfall.

SeanPatrick · 13-10-2022, 21:03

What Three Words has been around for quite a while now. Most people have never heard of What Three Words.

Those two facts should tell you something.

goboatingnow · 14-10-2022, 02:30

Quote:

Originally Posted by GrowleyMonster

That should simplify navigation. You only need to remember two words to make a perfect landfall.

Loads of gps coordinates have been mapped to this type of representation. It’s largely superfluous

Benz · 14-10-2022, 03:26

But the three words only describes a place, like Anvil Rock. It doesn't tell you how to get there nor how to avoid it. What three words could describe the passage from Key West to Isla Mujeres? How do you know which direction one square of words is from another?
Lat/long cordinates can pinpoint a place far more accurately than 3 meters square, with far less palaver, and gives you its relation to every other place.