Astro Navigation & Sextant

No one book covers everything -

Start with :
Tom Cunliffe - Ocean Sailing - Fernhurst ( good teacher )

then :
Kenneth Wilkes - Ocean Navigator - Adlard Coles ( more comprehensive - also good teacher)

and only then :
Mary Blewitt - Celestial Navigation ( assumes you know more than the basics )

most of the other books mentioned are too dry, for me a sense of humour is a very important part of teaching.

Get used to AP 3270 tables before you move on to NP 401 ( more confusing)

Dag Pikes book on the sextant is invaluable.

You might try those friendly people in Hull ( is it Henry Cooke ?) - I think they still make / repair sextants and they sometimes have 2nd hand refurbished ones for sale.
Make sure it's a micrometer one !!

good luck

Stephen


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Thanks for the advise Tony. Yup I was intending to do a course at some point, after a bit of background reading and playing.

I have in the back of my mind that there is a chap thats runs courses on sextants on the Brittany Ferry from Portsmouth to Bilbao (spain) ? Giving you experience at sea of taking sightings and plotting positions.

Good Luck with your RYA Yachtmaster Ocean Theory.




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Celestial Navigation Form

Back in '77 I bought a yacht in Sydney and, after preparation, spent a dream year cruising the Great Barrier Reef before selling the boat in Cairns. All this before GPS. I taught myself navigation before setting out - in doing so I was confused by the many different forms (in books) for the different sights and workings. I used my computer skills - in particular form design - to design a single 8" x 4" form (could be blown up) that literally coped with everything. I used it successfully all that year and never had to change a thing - got it right first time although I did put a lot of time and effort into it (learning nav at the same time). Other cruisers that saw the form were very impressed and I had lots of requests for a copy. I guarded it jealously as I could see that it had some monetary value and I had used skills - that took years to develop - to design it. For my own use I had made up pads of the forms. A lot - both good and bad - has happened in my life since and I lost track of my form. Going through all boxes of paperwork I have just today found a pad of the forms. Promptly scanned a copy for posterity and now seek to have others use it - without some sleazebag copyrighting my work. Advice anyone? I believe it to be a masterpiece of design but of course, with the GPS of today, may be of less value / use.
 
The Jester Forum on this site may be able to help. They ran a pre-Azores race celestial course a couple of years ago - cost £40, included a 4 year almanac, site reduction tables, star chart and site chronometer.
 
There are encapsulated pro-formas for sight reduction on www.cockpitcards.co.uk, one side is a completed example with notes indicating where the information is obtained, the other side is a blank form. Sights include Sun, Sun Meridian Passage, Planets, Star, Selected Stars, Polaris, Moon, Compass Deviation Check.

As a text book I would recommend 'Navigation for Offshore and Ocean Sailors' by David Derrick. Easy reading with good examples and enough table extracts for useful exercises. Out of print but does come up secondhand sometimes.
 
mineja said:
Back in '77 I bought a yacht in Sydney and, after preparation, spent a dream year cruising the Great Barrier Reef before selling the boat in Cairns. All this before GPS. I taught myself navigation before setting out - in doing so I was confused by the many different forms (in books) for the different sights and workings. I used my computer skills - in particular form design - to design a single 8" x 4" form (could be blown up) that literally coped with everything. I used it successfully all that year and never had to change a thing - got it right first time although I did put a lot of time and effort into it (learning nav at the same time). Other cruisers that saw the form were very impressed and I had lots of requests for a copy. I guarded it jealously as I could see that it had some monetary value and I had used skills - that took years to develop - to design it. For my own use I had made up pads of the forms. A lot - both good and bad - has happened in my life since and I lost track of my form. Going through all boxes of paperwork I have just today found a pad of the forms. Promptly scanned a copy for posterity and now seek to have others use it - without some sleazebag copyrighting my work. Advice anyone? I believe it to be a masterpiece of design but of course, with the GPS of today, may be of less value / use.
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They can't copyright your form - in designing and committing to paper your form.

I would create a document which contained:
* Cover page, title, author, date
* A page listing a Creative Commons licence for your work
* A page or more explaining how to use your form
* Your form

Post it on the internet (e.g. at ScribD or Lulu) and tell people how to get it.

Have a look at: http://wiki.creativecommons.org/images/c/cb/Ccplus-general.pdf and http://creativecommons.org/choose/
 
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Another vote for Tom Cunliffe! Concise and easy to use. My favourite.

Have used the Davies plastic sextant a lot. Not so good for stars, but great for learning and tolerates a bit of abuse. General snag is the mirrors tend to deteriorate a bit.

Got a metal Celestaire, dogs doodahs for stars. To find stars, try a look at Celestron Skyscout. Telescope with built in gps and Planetarium. Easiest way ever to identify stars.

All personal opinions only!!!!
 
My view is that the Adlard Coles Ocean Yachtmaster text book is heavy going but if you can stick with it and systematically work through each chapter you'll emerge with a great deal of knowledge.

I'm normally a big fan of Sir Tom but his book, IMHO, is perfect as a refrsher but lacking in detail to help you grasp the first principles.

The Mary Blewit book is, in turn, a refresher of the Tom Cunliffe offering, again, IMHO.

I may be dreaming but I think that I recall that the RYA has recently published a course workbook. May be worth adding to your library.

One post mentioned Smith. His coastal navigation book is brilliant so I suspect his astro version will be, too, albeit I've not seen it. Follows a similar learning process to that of the Adlard Coles but less heavy going.

I'd definitely stick with the AP3270 Vol 1-3 Air Tables "method". Please don't buy software to spoil half the enjoyment!

If you get hooked, which of of course we all know that you will, then buy American Practical Navigator by Nathaniel Bowditch.

A decent plastic sextant will suffice for a while until the lure of owning a piece of engineering excellence becomes to much to bear.

It's all about practice! On a reasonably clear day when the sun is visible, from, say, 10h00 to 16h00 local, you can take a forenoon, meridian passage and afternoon sight. Then have fun working out their respective position lines and the latitude of the MP. All the better if you were steaming for those 6 hours, you could then plot a sun-run-sun fix! You should use the sights to check the calibration of your compass at the same time.

Taking a night ferry is not necessary. This would be to shoot, say, 3 stars or plannets at civil twilight to derive a fix. Better to learn the skill using the sun first and practice twilight fixes later, at your leisure.

Just do it!
 
AIDY said:
Can anyone recommend any good books for a beginner to learn astro Navigation and using a sextant.

TIA

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On my Pacific trip I took a set of noon sights with one of these:

Davis Plastic Sextant

and found the Ed induced errors were an order of magnitude more than the intrument error.

The skipper had a much more expensive plastic sextant and we swapped sometimes but there wasn't much in it.

We didn't manage to get a star sight with either - you need a decent instrument with proper glass optics and front silvered mirrors etc. We found the stars would rack about half way down then disappear.

For working through the sight I followed the instructions in Tom Cunliffes book but I had to read it about 20 times for it to make sense - plenty of time in an ocean trip though.

For working it all out you will need some plotting sheets, an almanac and some navigators sight reduction tables.

On a good day I could get a position within a mile or so of the GPS. Certainly good enough to find a continent but I wouldn't like to have find the Marquesas.
 
AndrewB said:
Sextants are delicate instruments - you've probably heard that if a sextant is dropped its little more than heap of scrap metal. While sextants allow for certain adjustments and corrections to be made, some things like a warped or bent frame are uncorrectable.

Many of those for sale on Ebay sound useless except as ornaments. You might get lucky but unless the seller can definitely confirm it is fully serviceable or better still it is recently certificated, it probably won't be much use. What's more the genuine working ones command high prices, little cheaper than a brand new sextant. You'd be safer to go for a cheap(ish) plastic one from your chandler if you want proper results, something to learn with or as an emergency backup. An expensive metal one is for if you want to cross oceans without a GPS - or for those who wish to give the impression of doing so!

PS Another book is David Derrick "Navigation for offshore and ocean sailors", once the RYA recommended course book on astro-navigation, now long out of print but frequently available secondhand. I thought it good, avoids a cook-book approach.
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Well, disregarding the obviously ornamental brass sextants and the specialised sextants such as bubble or pocket sextants etc which make up 2/3rds of the eBay listings, I'd have no worries buying a sextant on eBay. Proper C-Plath, Freiberger and Tamaya (plus others) sextants show up from time to time, most people who own sextants really cherish them and I can't believe people go dropping them all over the place! Over the years, I've bought several sextants, mostly via eBay though some from Boat jumbles, and I've never been sold a dud! I'm sure there are some around but eBays not going to be full of duds I'm certain of that! Incidentally, one of the better Davis or Ebbco plastic sextants can provide very good results. Even the cheapo plastic models can provide reasonable results.

Cheers, Brian.
 
Astro Forms

I have devised a set of forms for all sights:

Mk l Beginners guides which spell out step by step what you have to do to complete the form.

Mk ll for those who do not need the guides.

Anyone interested, send me a pm.

Sticky
 
flobbergob said:
Well, disregarding the obviously ornamental brass sextants and the specialised sextants such as bubble or pocket sextants etc which make up 2/3rds of the eBay listings, I'd have no worries buying a sextant on eBay. Proper C-Plath, Freiberger and Tamaya (plus others) sextants show up from time to time, most people who own sextants really cherish them and I can't believe people go dropping them all over the place! Over the years, I've bought several sextants, mostly via eBay though some from Boat jumbles, and I've never been sold a dud! I'm sure there are some around but eBays not going to be full of duds I'm certain of that! Incidentally, one of the better Davis or Ebbco plastic sextants can provide very good results. Even the cheapo plastic models can provide reasonable results.

Cheers, Brian.
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I agree - no problem with lots of the 'proper' sextants on e-bay, and the one I bought isn't a dud and was a bargain.

Admittedly, I used a plastic Ebco special which was £5-00 at a jumble sale for years...
 
EdBeynon said:
On a good day I could get a position within a mile or so of the GPS. Certainly good enough to find a continent but I wouldn't like to have find the Marquesas.
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A mile or two is good with a sextant - great in the atlantic and brings you close enough for the radar to sort out. Not so good in the pacific if you are trying to avoid reefs, and some of the islands are so low that they dont really show on the radar.
 
Budgie said:
Around 30 years ago I bought a second hand bubble sextant, and with the aid of the book listed below, an almanac and some tables I was able to fix the position of Basingstoke to within 5 miles. I considered this to be an excellent achievement!

The very readable book, I have it still, is Little Ship Astro-Navigation by M.J. Rantzen, second edition, published by Herbert Jenkins in 1969, SBN257 65031 8, price 30s.

Much to my surprise I find that there is a second-hand one for sail on Amazon zshops for £4.00 +p&p!

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I also found the Rantzen book excellent: I preferred it to Blewitt. That was back in the mid-1970s, so Cunliffe's book was not written.
 
chart5011 said:
There are encapsulated pro-formas for sight reduction on www.cockpitcards.co.uk, one side is a completed example with notes indicating where the information is obtained, the other side is a blank form. Sights include Sun, Sun Meridian Passage, Planets, Star, Selected Stars, Polaris, Moon, Compass Deviation Check.

As a text book I would recommend 'Navigation for Offshore and Ocean Sailors' by David Derrick. Easy reading with good examples and enough table extracts for useful exercises. Out of print but does come up secondhand sometimes.
Click to expand...

Another vote for cockpitcards. I tried designing my own proformas and gave up when i saw these. Brilliant.
 
capnsensible said:
Another vote for Tom Cunliffe! Concise and easy to use. My favourite.

Have used the Davies plastic sextant a lot. Not so good for stars, but great for learning and tolerates a bit of abuse. General snag is the mirrors tend to deteriorate a bit.

Got a metal Celestaire, dogs doodahs for stars. To find stars, try a look at Celestron Skyscout. Telescope with built in gps and Planetarium. Easiest way ever to identify stars.

All personal opinions only!!!!
Click to expand...

Sorry but no. The easiest way to identify stars is to hold up your ipad with Star Walk in front of your face.
 
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