Navigational calculator / celestial navigation

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Larida

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Hi, I just registered to this forum and already have a question ;)

I just started to learn a bit about celestial navigation, read a variety of books which describe confusingly different methods and tables - I guess it takes some time and practice to get along with all that.

Nevertheless, I plan to buy a calculator that can help me checking some exercise calculations and maybe lateron also be of some practical help.

So it should be able to calculate with degrees and minutes, do all this sight reduction stuff and also calculate sailings and so on. In some books, the NC-77 is recommended - but I think it belongs more or less to a museum by now... Quite popular is also the TI-89 and some modifications with the "astrosail" software.

But are there always all the (usually tabulated) data included one needs - or otherwise where do you get them from?

My hope is that someone here in the forum can recommend me some good calculator - not too expensive if possible:) - and tell me where I can get it.
 
There's some software you can get to do this for you I believe. I'm not sure what it's called but someone here will know. Handy if you have a notebook aboard.

Any decent programmable scientific calculator will do what you're asking. Personally I prefer Casio but I do own a Texas Instrument's one and it was easy enough to program.
 
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Larida said:
Hi, I just registered to this forum and already have a question ;)

I just started to learn a bit about celestial navigation, read a variety of books which describe confusingly different methods and tables - I guess it takes some time and practice to get along with all that.

Nevertheless, I plan to buy a calculator that can help me checking some exercise calculations and maybe lateron also be of some practical help.

So it should be able to calculate with degrees and minutes, do all this sight reduction stuff and also calculate sailings and so on. In some books, the NC-77 is recommended - but I think it belongs more or less to a museum by now... Quite popular is also the TI-89 and some modifications with the "astrosail" software.

But are there always all the (usually tabulated) data included one needs - or otherwise where do you get them from?

My hope is that someone here in the forum can recommend me some good calculator - not too expensive if possible:) - and tell me where I can get it.
Click to expand...

Paper and pencil, possibly with some printed sight forms to use till you get up to speed. Celestial is now strictly a last-ditch backup, when all else has stopped working (as it can, given enough water chucked at it).
 
Another vote for paper and pencil. Suggest that you start with a sun sight and become reasonably proficient. Sun meridian passage, moon, polaris, planets and stars are all slight derivates of reducing the sun sight.

It really is not that difficult. If you're struggling with long-hand maths of adding and substracting in degrees, minutes and decimal, most cheap scientific calculators can be made to do this for you.

I don't subscribe to astro being consigned to a "last resort". Even as a recreational sailor, it's fun and there is huge satisfaction in fixing the position.

A cheap, plastic sextant will give reasonable sun position lines and they will improve with practice. You'll need much better optics by the time you've used AP3270 Vol 1 to set-up a twilight 3-point fix on the stars....but by then you'll be hooked!

Good luck
 
Hello, 'Larida'

This question comes up fairly regularly, and lots of peeps offer the stuff they happen to use. The same applies to 'how to do it' books - there are many of them, and only a handful are first-rate. The rest - the majority - are 'me too'.....

I've been doing this stuff over 30 years - The Queen paid for me to learn - and more recently I've taught it. My 'astro' bookshelf has more than a score of 'how to do it' books, and I've binned perhaps another score of 'em along the way.

The difficulty is due to the process requiring some capability with manipulating spherical trigonometry to 'reduce' ( resolve ) a sight into a usable Line of Position. As few of us are entirely comfortable with doing that from first principles, scores of shortcut methods have been suggested over the years. My old copy of 'Bowditch' ( American Practical Navigator ) lists nearly 60....

Most pro navigators ( a dying breed ) would agree it matters that you 'n I should have some degree of understanding of what we're trying to do when we reach for a set of 'look up' tables and/or a nav calculator, so we can understand/identify/correct some of the many little errors of procedure that bedevil our workings.

For my money ( literally ), I'd encourage anyone starting down this path to invest in several documents/books:


A: RYA Astro Navigation Handbook ( Bartlett ) for a lucid explanation of what one is trying to do.

LatestScans-1.jpg



C. Reeds Astro Navigation Tables 2012 ( Cdr Baker ) - including the year's tables-information, explanations, and a straightforward method of working out your sights both with and without a calculator. This is the route I take on a small sailing craft.


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C. Selected 'Laminated Sight Reduction Forms' from here


There are dozens of sight reduction forms, most of them confusing and likely to lead astray everyone but their inventors. The laminated ones - I use 'em - are clear, robust and can be copied.

The other most useful resource is a mentor or coach. Everyone makes mistooks in their astro. The most frequently-heard call is not 'Where am I' but 'What have I done wrong now...?' and one's tutor/coach is invaluable in keeping the frustration at bay. ;)
 
Thank you for so many answers - I didn't expect that...:)

Well, personally I agree with those of you who prefer a pencil+paper solution... (maybe because I am working with computers...). I am currently reading 3 books about celestial navigation and have one more on the shelf - not the RYA book you recommended, though. The different techniques described there are surely very interesting, and I will use the winter months to get some practice in using some of them.

However, after hopefully having collected some of the remaining miles next spring, I plan to prepare for the next and last sailing exam, which in my case is the german SHS (Sporthochseeschifferschein). Unfortunately, it was decided last year that a calculator has to be used for this part of the exam in navigation instead of the tables. So, if I want to do this, I have to buy a calculator, and it may not be a PDA or laptop or iphone... So even if I learned to be as fast with the tables as a calculator, I would not be allowed to do the calculations like this. Therefore my question.

The TI-89 is used by most of the schools, also the professional ones, but I thought there could be an alternative.
By the way, how do they do this in the RYA courses - I was told that they also changed to the calculator-solution?!
 
davidjackson said:
............. I don't subscribe to astro being consigned to a "last resort". Even as a recreational sailor, it's fun and there is huge satisfaction in fixing the position.
Click to expand...

Nor do I, it gives you something interesting to do on a long passage, and it remains a useful skill to be able to work out that you are within a mile or two of the GPS position!!

Mind you the last time I brought my sextant aboard a yacht when going as navigator on a long race there were complaints that it was the heaviest thing on board except the anchor.

I still do carry a sextant and tables etc on the rare occasions now I go offshore, as I have more than once been on boats with all electronics dead.
 
jwilson said:
I still do carry a sextant and tables etc on the rare occasions now I go offshore, as I have more than once been on boats with all electronics dead.
Click to expand...

Yes, I just experienced this again some weeks ago in Norway, where the GPS sometimes was unavailable (e.g. due to the fjords).... some days later stopped working - at least much later than the chart plotter, but why do people have to install such things in the cockpit of charter boats?!

So - I did not want to start a discussion about whether it is useful to navigate without electronics, but I explained in my last post why I probably have to buy another electronic device...
 
There are Javascript sight reduction systems; these should run perfectly happily in the built in browser on a smart phone. If you download the web page and the Javascript, they should run without web access. All you need for those is an ephemeris for the celestial bodies you intend to observe. There are others; the one I linked to happens to be the first on Mr Google gave me!

By the way, there is little or no mystique about spherical trigonometry; there are only two basic relationships you need to know; the Sine Rule and the Cosine Rule. I admit that applying them isn't always straightforward, and you need an appreciation of when the naive use of them can go wrong! But your "position line" is simply a small circle centred on the nadir point of the celestial body you observed, with an angular radius equal to the complement of the observed (and corrected) altitude.
 
 
A TI-89 loaded with Starpilot software has a built in almanac for all celestial bodies and will do everything you are ever likely to need in astro-nav with an absolute minimum of effort. It is quite expensive, but useful for very quick results and for checking solutions arrived at by other means. It is unlikely to be allowed in exam situations.
A much simpler, low cost and non-programmable calculator is the TI-30XA, with just three memories. A few key presses will solve the cosine formula. You will need an almanac and if you don't want to rely on the internet for this or don't want to buy a new one each year, I would recommend Geoffrey Kolbe's Long Term Almanac, which is simple to use and good until at least 2050.
No connection with Texas Instruments or Dr Kolbe! Google will quickly supply links to the above.
I would also recommend Navlist at www.fer3.com for anyone interested in astro navigation. There have been many discussions on Navlist on suitable calculators, other methods of sight reduction and much else.
Good luck.
 
Lady Campanula said:
. . . For my money ( literally ), I'd encourage anyone starting down this path to invest in several documents/books:


A: RYA Astro Navigation Handbook ( Bartlett ) for a lucid explanation of what one is trying to do.

LatestScans-1.jpg

. . . . . .
Click to expand...

Do you think that if I spoke very, very nicely to the author chappy, Tim, he might send me a free copy? :D
 
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