Sextant and astro/nav

cagey

cagey

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20+ years ago I did shore based astro/nav course to get my Y/M Ocean cert. needless to say I’ve forgotten everything. Ive just bought frieburger sextant with the idea of relearning Astro both to fend off boredom and stimulate ageing brain bits. Could anyone please recommend an easy to understand book that will cover the maths and the practical sextant bits.
I'm looking for the impossible an easy to read and assimilate book that is both interesting, easy to read but not intimidating.
If it takes 2 books then that’s what it is. Did I say the books need to be cheap.
An online course would be ok.
Thanks everyone
Keith
 
Hi Keith .. surely it has to be Mary Blewitts ' Celestial Navigation for Yachtsmen ' ! My 4th edition is 1964 but have a look on Amazon for the 13th edition. 10 quidish. Cheers Phil
 
There are many text books available suitable for different needs and learning abilities.

The Mary Blewitt book is very brief but intense, it’s all there but not necessarily and easy read. It’s very good as a revision document, imho.

Tom Cunliffe is always an easy and informative read.

I don’t have the RYA book so can’t comment.

I did the course (about 15 years ago) as a 5 day, one to one intensive. I got through it but didn’t fully understand so I bought a few text books and repeated the coursework by myself until the proverbial penny dropped. The best book, by far, for me was Adlard Coles Ocean Yachtmaster.

These days, I now teach the course ?
 
Look at www.backbearing.com - you will find almanac and sight reduction tables for the Sun and in the 'Links' page, Andrew Evans' Sextant user's guide which will tell you all you need for Sun sights. I'm envious of your Frieburger - I have an Ebbco plastic. Am getting position lines within a couple of miles, though!
 
Celestial Navigation in a nutshell by Hewitt Schlereth. Quite the most user-friendly of them all. Problem with Mary Blewitt etc is that they are all locked into the stone age sight reduction tables. "chosen positions" and rounding up/down to the nearest degree are history. Strongly recommend that you look on line for advice on how to resolve the PZX triangle by using a very basic calculator (cost about £5) and the sine and cosine formulae. As well as online advice the trig. method is also explained in the back of the nautical almanac. Dragging along weighty and expensive tomes is a thing of the past.
 
john_morris_uk said:
FWIW, I find Mary Blewitt’s books much less of an easy read to Tom Cunliffe.
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Totally agree. I think it was probably good in its era but its very heavy on theoretical detail. Most of the Ocean students we have had over the years find it just too much hard yakka.

The two short books our guys n girls have got on best with over the years have been the Tom Cunliffe one mentioned and Tim Bartletts RYA book. I like to use a combination of both to get the best bits. Quick and concise on the background theory but great for the practical application of fixing which is what most people want to know.

For self study there is now masses on youtube to help.

Its not the black art most people worry about. But very satisfying once you get the hang of it. Very popular at the moment with online distance learning too.

Enjoy your refresher!
 
Malabar said:
Celestial Navigation in a nutshell by Hewitt Schlereth. Quite the most user-friendly of them all. Problem with Mary Blewitt etc is that they are all locked into the stone age sight reduction tables. "chosen positions" and rounding up/down to the nearest degree are history. Strongly recommend that you look on line for advice on how to resolve the PZX triangle by using a very basic calculator (cost about £5) and the sine and cosine formulae. As well as online advice the trig. method is also explained in the back of the nautical almanac. Dragging along weighty and expensive tomes is a thing of the past.
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I'm all for people solving the PZX triangle by whatever means they have available, but to dismiss AP3270 as Stone Age is a bit OTT IMHO. (No complaints about the TLA's please because one is a FLA...)

Astro can be a seen as a get you home of last resort and to surmise that you're going to have a working calculator might be an assumption too far. On a boat sailing across an ocean you'd still need a Nautical Almanac and the bare minimum after that would be the one set of AP3270 for the latitudes you're in. Not such a big ask.

Whether they are expensive is another matter. I got mine second hand on eBay years ago. There's a set on offer for £39 on eBay at the moment (although you can sling the 'Selected Stars' as the epoch is way out of date...). A complete set (again with the wrong epoch for selected stars) sold for £15 a little while ago.
 
Re using a calculator or computer: I can see it's real advantages as a fast method of checking how accurate your sights are when in a near exactly known position, but a very bad idea to rely on it in earnest, when you are mid-ocean, and all your electronics are out including the supposedly "waterproof" handheld GPS. I was once there, took the Garmin handheld to bits and dried it out in the oven. It worked again afterwards, but it might not have. That was the second time in my life that a well-found yacht had a serious excess of salt water below deep-sea and lost most electronics: I did have sextant and tables aboard. Doesn't help if skies obscured, but sooner or later they will clear.

I don't totally rely on non-electronics, two cheap 200 metre waterproof Casio watches really do seem to be genuinely waterproof, but even if they both died you can still easily get latitude, which is a lot better than nothing.

Sextant now is for two things: last ditch "break glass in emergency" navigation, and avoiding boredom on long passages so you can say your sights say the GPS is 1.6 miles out!
 
john_morris_uk said:
Astro can be a seen as a get you home of last resort and to surmise that you're going to have a working calculator might be an assumption too far. On a boat sailing across an ocean you'd still need a Nautical Almanac and the bare minimum after that would be the one set of AP3270 for the latitudes you're in. Not such a big ask.
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Just the one pair of rarely used esoteric volumes?
 
neil_s said:
Look at www.backbearing.com - you will find almanac and sight reduction tables for the Sun and in the 'Links' page, Andrew Evans' Sextant user's guide which will tell you all you need for Sun sights.
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Not only is it absolutely free, its also the very simplest and easiest to understand approach to navigating by the sun. I wrote it because I read 5 other books and still could not understand what the heck they were talking about.
 
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