Good beginners guide to celestial navigation

[TQA]

I have reservations about blindly following the 'recipe' as a navigation tool. Although I did use a small programmable calculator when I was taking sights for real and just entered the numbers as directed and relied on the figures it produced. However I had taken the trouble to make sure I understood the principles behind what I was doing and could at a push do it long hand if needs be.

I was haunted by the story of a single hander who had set off across the Atlantic aiming for an island in the Caribbean and on making landfall found out he was in South America because he had not understood that there was a point at which a correction was added and not subtracted. [ Purves maybe ? ]

 

[alant]

I have reservations about blindly following the 'recipe' as a navigation tool. Although I did use a small programmable calculator when I was taking sights for real and just entered the numbers as directed and relied on the figures it produced. However I had taken the trouble to make sure I understood the principles behind what I was doing and could at a push do it long hand if needs be.

I was haunted by the story of a single hander who had set off across the Atlantic aiming for an island in the Caribbean and on making landfall found out he was in South America because he had not understood that there was a point at which a correction was added and not subtracted. [ Purves maybe ? ]

Well, the position line derived, is just part of a large circle, the trick being to decide where on that circle you might be.
Obviously if your feet get wet when you dangle them over your threshold, you can eliminate the green bits on your chart.

 

[capnsensible]

Well, the position line derived, is just part of a large circle, the trick being to decide where on that circle you might be.
Obviously if your feet get wet when you dangle them over your threshold, you can eliminate the green bits on your chart.

Surprisingly true about overlooking the obvious. I think that's the practical side that doesn't get mentioned. Someone on here, Mebbe Uricanejack? Said that yer first thousand sights aren't as good as yer second.

I did the course but didn't really understand til I went and did them.....only in me hundreds! Lots of them were total pants. That's when, I reckon, you start to learn. Grab a quick sun on a cloudy day, bit knackered from watch keeping, position line all wrong, puts you the other side of planet Zog. Do you give up, chase it through, what?

Have you used wrong lat, contrary rather than same, wrong Lha? Just been daft with adding up?

The main things I learnt was the earth stands still, the rest of the stuff goes round and you only get good with practice. And when you get that fix from something a gazillion miles away, it's like winning the cup final.

There again, have eleven teen gps things on board and be bored......

 

[Barnacle Bill]

Surprisingly true about overlooking the obvious. I think that's the practical side that doesn't get mentioned. Someone on here, Mebbe Uricanejack? Said that yer first thousand sights aren't as good as yer second.

I did the course but didn't really understand til I went and did them.....only in me hundreds! Lots of them were total pants. That's when, I reckon, you start to learn. Grab a quick sun on a cloudy day, bit knackered from watch keeping, position line all wrong, puts you the other side of planet Zog. Do you give up, chase it through, what?

Have you used wrong lat, contrary rather than same, wrong Lha? Just been daft with adding up?

The main things I learnt was the earth stands still, the rest of the stuff goes round and you only get good with practice. And when you get that fix from something a gazillion miles away, it's like winning the cup final.

There again, have eleven teen gps things on board and be bored......

If you do the sight reduction using a form, and the result comes out mad, you (or someone else) can check it. Don't throw it away - check through it, find out where you went wrong, and you have learned something. After a few goes, the form will guide you through the process.

 

[alant]

Surprisingly true about overlooking the obvious. I think that's the practical side that doesn't get mentioned. Someone on here, Mebbe Uricanejack? Said that yer first thousand sights aren't as good as yer second.

I did the course but didn't really understand til I went and did them.....only in me hundreds! Lots of them were total pants. That's when, I reckon, you start to learn. Grab a quick sun on a cloudy day, bit knackered from watch keeping, position line all wrong, puts you the other side of planet Zog. Do you give up, chase it through, what?

Have you used wrong lat, contrary rather than same, wrong Lha? Just been daft with adding up?

The main things I learnt was the earth stands still, the rest of the stuff goes round and you only get good with practice. And when you get that fix from something a gazillion miles away, it's like winning the cup final.

There again, have eleven teen gps things on board and be bored......

If you need reassurance, I'm quite happy to take you through the RYA course again, mates rates/expenses in the Canaries, my suntan needs a top up.
We can get confused together.

 

[capnsensible]

If you do the sight reduction using a form, and the result comes out mad, you (or someone else) can check it. Don't throw it away - check through it, find out where you went wrong, and you have learned something. After a few goes, the form will guide you through the process.

I fear you and alan may have missed the point......

I'm pointing out the bits they don't teach in a normal course. Having a nice comfortable ten transats under me belt with hundreds of sights, My post was to warn people of what it's like when reductions go wrong, you are tired, mis add up and the many other things that put your position line somewhere beyond Pluto.

It's quite common foreople to simply read the sextant angle wrongly or something that seems simple in the classroom. Don't worry alan, I've passed this sort of stuff on to all the students on ally the astro courses I've taught over the last fifteen years......

My best student at sea is my wife. She is an Ocean Yachtmaster too! :encouragement:

Oh yeah, alan, if you do make it to the Canaries I can show you how to dock a yacht too!

 

[alant]

I fear you and alan may have missed the point......

I'm pointing out the bits they don't teach in a normal course. Having a nice comfortable ten transats under me belt with hundreds of sights, My post was to warn people of what it's like when reductions go wrong, you are tired, mis add up and the many other things that put your position line somewhere beyond Pluto.

It's quite common foreople to simply read the sextant angle wrongly or something that seems simple in the classroom. Don't worry alan, I've passed this sort of stuff on to all the students on ally the astro courses I've taught over the last fifteen years......

My best student at sea is my wife. She is an Ocean Yachtmaster too! :encouragement:

Oh yeah, alan, if you do make it to the Canaries I can show you how to dock a yacht too!

Why do I need to be shown how to dock a yacht, I, know how to use springs.

 

[KellysEye]

Mary Blewitt's instructions are much clearer than Tom Cunliffe's who tend to complicate things to make taking a sight look difficult. Two tips it's much easier to take a sight by turning the sextant upside down then find the sun and then bring the horizion up to the sun, make sure the shades are set right. Also we did carry astro tables but it is much easier to use a progam http://www.astrocalc.com/ 32 and 64 bit, make sure that it works on the software you have Widows 8 software normally works on Windowss 10 but do check with them.

 

[AHoy2]

..........
I was haunted by the story of a single hander who had set off across the Atlantic aiming for an island in the Caribbean and on making landfall found out he was in South America because he had not understood that there was a point at which a correction was added and not subtracted. [ Purves maybe ? ]

You are probably refering to Les Powles on his first circumnavigation aboard Solitaire. Les mentions this and his novice approach to navigation in his book Solitaire Spirit (available on Kindle).

 

[janyon]

I cant recommend a simple book mainly because I'd not found one, most seem to want to teach at least some of the spherical trig that underlies astro nav. Having got, in the first ten minutes or so, that astro relies on a variant of the running fix what I really wanted was a set of steps to work up that fix. Sure, there are a lot of variables and getting them in the right order is vital but with a decent proforma, or a spreadsheet, its not especially difficult - but it does require concentration. Foolish Muse's stuff looks pretty good on a swift scan

I might just take a look... Thank you

I want to buy a sextant for my husband who has become interested in sailing and need advice. cost is a concern but I don't want to buy a useless instrument. I am at sea here. Can anyone provide some purchasing guidance?

 

[Mark-1]

Another vote for Tim Bartlett's book from me. Can't see how he could have made it any simpler. Two evenings and I was able to calculate the position of my back garden. (I was miles out but that was shakey hands and a home made sextant, not the maths!)

RYA Astro Navigation Handbook: Amazon.co.uk: Bartlett, Tim: 9781906435097: Books

 

[Barnacle Bill]

Have a look at Reeds Ocean Handbook. There is a step-by-step guide, aimed at people who would normally rely on GPS but want to have access to pencil-and-paper astro method for an emergency.

Reeds Ocean Handbook
Reeds Ocean Handbook: Amazon.co.uk: Bill Johnson: 9781472913067: Books

 

[Humblebee]

Thanks to all who have posted links to online resources, as well as the book recommendations. I'm a novice and found much that is helpful in this thread.
Just one other observation, I sometimes find that if one person's explanation doesn't make a thing clear, try another author. It is as if one person's style of writing doesn't suit us but someone else's does. Comparing different explanations from different sources can be helpful too.

 

[jdc]

I want to buy a sextant for my husband who has become interested in sailing and need advice. cost is a concern but I don't want to buy a useless instrument. I am at sea here. Can anyone provide some purchasing guidance?

I take this to mean the sextant itself rather than a book telling how to use it (which is the main subject of this thread).

Almost any sextant can be used given an absolute need, but here are some I know about.

For my first ocean voyage in 1991 I had to use a sextant (pre GPS) and could only afford a plastic one (an Ebco Special). It worked, and I've still got it, but one has to get used to not gripping too hard lest it distort, and star-sights are not that easy. Davies plastic sextants are apparently a bit better and still available from Amazon.

However if you are getting it for the satisfaction of the thing rather than through desperate need, it's much nicer to use and own a good one! Plastic is still ok to reasonable quality - the Davies mk 25 is quite a sophisticated beast but is £270 odd from new.

You will almost certainly be buying second-hand - nothing wrong with that at all - but it is essential to get one made for navigation use rather than an 'objet'. Words in the listing to avoid are 'brass', 'antique', 'vintage' or 'Russian'. You want something made post WW2, and probably it will be grey painted aluminium. It must have a proper telescope and drum micrometer. Excellent makes are Freiberger, Tamaya and Plath. They come up on eBay from time to time (this one for instance: Freiberger Drum Sextant With Detachable Telescope | eBay) but note the price - not a lot of change (if any) from £500. A few days ago on the ybw for sale forum there was a decent, albeit a bit low-end model, Freiberger for £220 iirc.

Doubtless others will chip in with their favourite makes and models (mine's a Freiberger with proper telescope and full-horizon viewer which I got on eBay in 2007 for about £500). No brass visible, and I want none.

Edit: added Plath

 

[DownWest]

I want to buy a sextant for my husband who has become interested in sailing and need advice. cost is a concern but I don't want to buy a useless instrument. I am at sea here. Can anyone provide some purchasing guidance?

Interesting you bought this thread up to date.. If hubby is interested in sailing, then Astro Nav is slightly in the future for him. Not so many people use it now, just buy spare SatNavs at little money..Learning to sail is covered frequently on this site, and does not include looking at the sun and stars to find your way. Coastal navigation is different and much more down to earth with lights and bouys, tides and depths. Better start there.

Edit, missed the post above. Just depends if hubby wants to actually sail, or just think about it.

 

[Sharky34]

Hi

I am going to be doing my first ocean passage in January, across the Atlantic, and I'm keen to use the opportunity to get some experience at celestial navigation. However, I am an absolute beginner in the subject and would be grateful for any suggestions for good beginner and introductory guides.

Also, apart from a sextant and a copy of Reeds Astro Navigation Tables for 2017, will I need anything else?

Thanks for any suggestions

Some idea how to reduce your sights from the tables (include an almanac)