The basics of the sextant explained by Tom Cunliffe. ©Tom Cunliffe

A quick look at the basics of Tom Cunliffe's sextant from his boat on the Beaulieu River.

[@robinj.9329]

The "Marine Sexant" is both simple and wonderful. Using only some basic principles of optics, physics and mechanics, we have an instrument that has been used by Mariners, merchants and Explorese to navigate the world since the 1700's. From Captains Cook and Blye. To my Grandfather in the 1960's and 70's. And is still used today by "Real" sailors and Mariners. If you don't fully trust GPS, you need to understand Celestial Navigation.

[@theartfulbodger]

Nearly 40 years ago I met Tom when I tied up on a visit to the Beaulieu river. After years of reading his articles in the mags. I was pleased to have a chat with him and found him a very friendly fella! When I saw his book on astro in a bookshop I bought it because I liked him, and I was struggling with Mary Blewitt's very good book on the subject. Tom's book should be called "Astro for dummies" because it taught this dummy well enough to cross the Atlantic and the Pacific purely with a sextant and tables and compass. Once I was "hands on" with using my sextant and finding a position, Mary Blewitt's book made more sense to me and filled in more detail. Very pleased that a chance meeting with a very nice guy led to solving my navigational learning issues. Thanks Tom

[@TomCunliffeYachtsandYarns]

Hi Colin. Good to hear from you after all these years. Thanks for your kind remarks. I'd like to put your words up on my website in the book section. OK with you? All the best Tom

[@theartfulbodger]

@@TomCunliffeYachtsandYarns By all means Tom, I hope it brings in a few more sales. Your book was a game changer for me with astro, many thanks for writing it. All the best Colin

[@TomCunliffeYachtsandYarns]

Many thanks! It's up on my site now. Tom

[@aljotock]

I could listen to you for hours! So relaxed because you’re so knowledgeable!

[@oldsailor5711]

Everybody in the Netherlands declared I was nuts with my walker and sextant and up to date navigation tables, they say that it's useless nowadays, it maybe is until the battery quits in the middle off an ocean. I still use it regularly just for fun and it keep u up to date with it

[@TomCunliffeYachtsandYarns]

So do I, Old Sailor. It's fun too and it's good to see a growing number of young sailors taking an interest - at least in the English-speaking world

[@grafitember]

@@TomCunliffeYachtsandYarns Not only in the English-speaking world! We don't have seas and coasts, but curiosity here, in Hungary. Cheers from here! I love your work.

[@suzyqplacet]

In a perfect nutshell! This subject always makes me chuckle. In our travels we have come across private gin-palaces and other such floating temples to technology, absolutely laden down with more electronic equipment than they can use or need and yet, these monsters have been stuck in port because they have some sort of ill-function! In our old 1912 floating home we had what I feel was the basics: a sextant, a Walker's Log, a lead-line with chewing gum on the bottom, a WW2 Spitfire compass and a 1946 Dorman diesel engine , a large whale-gusher hand pump, some sturdy sails and ... that was IT! No radio, no depth-sounder, no GPS, just good charts, plenty of time , common sense, a hammer and screwdriver and we NEVER ONCE got stuck in port by anything other than a howling gale. I'm really happy that someone has seen sense - not having the basic "old-fashioned" material could cost lives. Well done U.S. Navy!

[@750count]

I absolutely applaud your style

[@TomCunliffeYachtsandYarns]

Suzy. You've said it all, really. So many people fall into the trap you mention. I've got one foot in it myself these days and I often remember with deep happiness the days when we sailed the seas exactly as you have described. Thanks for taking the trouble to remind us all of what matters. All the best Tom

[@suzysaudiostorycorner1366]

@@TomCunliffeYachtsandYarns Hi there, Tom! How lovely to hear from you. Yes, as time goes on we seem to be more and more dependent on electronics and the cyber life - quite frightening! But, comforting to know that in the maritime domaine one can chuck it all overboard where it belongs and still be safely independent. I hope you and your wife are in fine form and that you are still happily sailing the seven seas. All the best, as ever, Suzy

[@AfricanFlightStar]

Always wanted to learn how to use a sextant, now you've convinced me to do it! Was going to make one using my 3D printer (many plans avail online) but I also love a tool with history attached to it, so will see if I can find a genuine WWII era sextant out there. Thanks for sharing that 👍🏼☺️

[@TomCunliffeYachtsandYarns]

Hoping to make a series of videos about sextant use in the next year which will be up on my website. Those old sextants are lovely, but beware - some of them have been too highly polished and you can't read the figures. Tom

[@Ploddingalong67]

Shakespeare and sextant, a cultural hit rare and exciting. Great to have a basic explanation of this art. Yet to be learned by yours truly but looking forward to doing so. Thanks for the post.

[@sailingluckybear1045]

This is a Skill I do need to learn, Thank you for this video, I cant wait to get a Sextant and start practicing :)

[@TomCunliffeYachtsandYarns]

You won't be sorry. Buy the book 'Celestial Navigation' from my website and I'll sign it for you.

[@sailingluckybear1045]

that would be great, thank you! I need a month or so (been unemployed for 3 months) need to stabalise alittle then I will grab it for sure.

[@c5back9]

Well, I hope things have improved for you since last year, but given all this COVID, I wouldn’t be surprised to hear that times are still tough. How about an update though? Have you been able to get Tom’s Celestial Navigation book?

[@sailingluckybear1045]

@@c5back9 Hi there, Things have been not great the year started good with more work then the last 3 years.... but March all my contracts and jobs got cancelled and back to no work since the lockdown.... I am living at the house where will build the boat, and have cleared the land and did everything can do that does not include a big expense.... just need some work again and moving forward.... hope by November something may come up..... 8 months with no work as an expat is very hard.... no work means 0 money.... if was in Canada at least have unemployment insurance and welfare, here I have what is in the bank..... and thankful a low cost of living (about $300 a month all in)... wow long reply :)

[@maxflight777]

Clearly, before inertial navigation was adopted, this was the only method of navigation for aircraft out of range of ground nav aids. For example, when crossing oceans. If you look at the flight deck on an any 747, a sextant could be installed into a hole in the ceiling, just aft of where the flight engineer used to be seated. An adjacent lever is pulled to open the outside end of the hole. The snug fitting sextant was then pushed a few inches further into the port so as to protrude outside the cockpit roof.

[@seanmulligan1339]

Well their warships keep colliding with folk🐳there is also the equation of time that should be mentioned perhaps we should have sundials aboard🐳🐳🐳

[@alwynjones7218]

As always Tom, a very interesting and Informative post, time I added it to my skills.

[@Blastfence1]

Tom’s book 📖 on celestial navigation 🧭 arrived today just got it out of the mailbox 📬 looks wonderful can’t wait to dig in! The entire book 📕 is full of wonderful color illustrations. I highly recommend buying Tom’s book 📖!

[@garygerard4290]

best 5 minutes on U Tube, thank you

[@reloadncharge9907]

Good one.....my old Heath sits proudly in its box onboard my cat...ready for the day, charts and almanacs at hand! Thanks, Andrew

[@ximono]

0:33 "But anyone with any brains at all takes one with him, and he knows how to use it." A brain, you mean?

[@blik2108]

Excellent. I hadn't thought about plotting 2 latitude lines a few hours apart. Much easier than timing the highest point and then working out longitude I guess. realistically how accurate have you found it over the years

[@karlsmith5935]

another fine little video tom keep up the good work kind regards Karl

[@tincoffin]

I remember my dad learning how to use one . He was sitting on the shore at Lymington not far from where Tom is now and found himself in the middle of Worcestershire . It takes practice.

[@TomCunliffeYachtsandYarns]

I often take my students down to Barton on Sea as you get a good southern horizon from there. In fact, I have a pupil coming tomorrow, so let's hope the fog doesn't roll in. Tom

[@tincoffin]

@@TomCunliffeYachtsandYarns Many thanks for your reply. Just to warn you - they now charge for the car parks which used to be free from October to March . There is usually a space on the sea front at Barton .

[@Inkling777]

In Sailing Alone Around the World Joshua Slocum mentions navigating with an old alarm clock that had only a minute hand. I've heard that can be done using sightings of the moon. If you get a chance, you might explain how that is done. I assume that's the same two-sighting trick with the minute hand telling the time between.

[@TermiteUSA]

Joshua was amazing. Maybe he was really Spock in the holodeck.

[@williamturner1517]

March, 1986, I was super cargo on a freighter from Germany to Texas. Mid way across the Atlantic, I ask the 2nd mate, Do you have a sextant ? "I'm sure we do, somewhere."

[@Dj1deck]

Hi Tom, if we’re using the horizon to establish horizontal on the surface of earth in order to obtain an elevation angle, then the sea in this case must be horizontal and not curved, would you agree ?

[@robertlafleur5179]

Would Tom agree? Short answer: No. Long answer: NO. Celestial Navigation is done with Spherical Trigonometry, that's SPHERICAL as in SPHERE. Spherical trig does NOT work on flat surfaces hence Earth is a sphere. Could you solve this Celestial Navigation problem using ''flat earth science'' only since you seem to think that seas are flat and not curved? Here are 3 star sextant's sights: The date is July 6, 1993. Time UTC Star Sextant height 14:38:33 Fomalhaut Hs = 20°52.0' 14:41:37 Capella Hs = 26°01.0' 14:43:05 Vega Hs = 38°47.7' Height of eye = 9 feet. Sextant index error = 1.5' on the arc. Where was the observer? Remember, you can only use ''flat earth science''. Show all your ''flat earth science'' calculations, you can't cheat by using globe science. No flat earther has ever demonstrated flat earth Celestial Navigation. Good luck!

[@Dj1deck]

@@robertlafleur5179 Tom would be incorrect then

[@robertlafleur5179]

@@Dj1deck Why would Tom be incorrect? Oceans do curve.

[@Dj1deck]

@@robertlafleur5179 incorrect sea level is a mean sea level

[@robertlafleur5179]

@@Dj1deckMean sea level is the average height of the sea between high tide and low tide. It does not mean that oceans are not curved.

[@PrinceKlutz]

As always another fine vid, Tom!

[@guillermogouldburn763]

I'm bald at 30 and look at you.

[@TermiteUSA]

On the Chesapeake as a kid I watched my pops practice for his USPS Navigation class. The sky now has about 30% of the stars visible with night city lights over the horizon from the WNW thru the NNW. Still love it when anchored up though.

[@abidelao9221]

This video is great!!

[@pdczrwnskz]

Neat.

[@captainheather]

Oh how I’d love to see you do a whole class on Astro navigation online!

[@TomCunliffeYachtsandYarns]

Well, I have plans to do some Masterclasses on my website www.tomcunliffe.com. At present, I'm expanding it, but watch this space. Tom

[@AndyUK-Corrival]

I bought a Heath Sextant a couple of years back but it needs calibrating so need to get it to Mr Robinson in Hamble to look at. Mirrors are a bit crusty too but should be ok. Then I need to get to work as I have not had a good crack at mastering the Sextant but it is something I want to do. Thanks for this as it has prompted me to get on to it. Andy UK

[@LeonardSkinnerOfficial]

Only Tom Cunliffe could sum it up so perfectly :-) Now, if only the boat would let me afford a sextant, it's one or the other, I can't have both!

[@sailingcorribeemwera]

Great little vid, thanks, think if I went across the oceans I'd get into this

[@nickwebb9290]

Having a sextant and being able to use it makes serious sense, who wouldn’t not have one or the lanyard to go with it

[@mikedale6783]

Great lessons ! Thanks ! What size boats do you use to cross the Atlantic ? Keel stepped mast ? Also, what type keel, if you would ,please ! Thanks.

[@TomCunliffeYachtsandYarns]

Hi Mike. Pleased you are enjoying the vids. There's no straight answer to your question, but for me it's a keel-stepped mast and a full keel. You can read more about hull forms etc in my book, 'The Complete Ocean Skipper'. It's available from my website www.tomcunliffe.com. I'll even sign it for you! Tom

[@redjacc7581]

always learn the fundamentals, you just never know when tech will fail.

[@TomCunliffeYachtsandYarns]

Well said. Tom

[@williewonka6694]

Excellent lesson in a nut shell from a man of greT experience, Thanks Tom

[@TomCunliffeYachtsandYarns]

So pleased you enjoyed it John.

[@VGrillone]

Wonderful Tom!

[@jonelliott9157]

You’ve just inspired me to get a sextant, learn it and put it to work. Thank you, Sir!

[@TomCunliffeYachtsandYarns]

That's great news Jon. Do buy my book 'Celestial Navigation' which will help you get to grips with it. It doesn't cost much and it's available on my website www.tomcunliffe.com I'll even sign it for you! Tom

[@jonelliott9157]

I’m on it! Thank you, Sir!

[@gurglejug627]

Astro Nav is back on the curriculum not least because the Russians can jam GPS signals

[@DaveWatts_ejectamenta]

Jamming the entire ocean would be quite difficult I think, a bigger problem is if they decide to turn GPS off altogether for non-military people.

[@karhukivi]

@@DaveWatts_ejectamenta They don't need to jam the entire ocean, have a listen to what this navigation officer says: kzbin.info/www/bejne/b3qsfqWhZbalf7s

[@jimkobe64]

Fascinating!!

[@MrFergus53]

Tom I maybe late with this comment but in a nut shell thanks for the quick understanding of why the sextant is used, Having spent my youth in the Navy until I finished up I was in the Nave Dept. as a Radar Plotter and even though I saw it being used a lot by the young snottys learning their seamanship I didn't know how too use one even though I could have to round out my education in navigation at sea. now mostly I watch you tube channels of other SVs only one of them I have seen (though they have all the Nav aids) they still use the sextant (a Canadian Cpl)so not all is lost as most channels that I watch all use the nav aid they have and astonishing enough they don't possess a sextant....

[@TomCunliffeYachtsandYarns]

Hi Mr F. I believe that the US Navy have brought celestial navigation back into their syllabus. Certainly over here in UK a rudimentary knowledge is required for the RYA Ocean Yachtmaster.

[@iainlyall6475]

@@TomCunliffeYachtsandYarns ryan on sailing kittiwake is practicing with a sextant for navigation. nobody else that i'm aware off.

[@rocketspushoffair]

It's not 93 million miles away. A sextant is "an instrument used to measure the altitude of any object above the surface of the earth" and that includes the sun. Great video by the way. But you and I both know, you are not using 93 million miles away in any calculation, let's be honest here. :)

[@TomCunliffeYachtsandYarns]

Thanks for this. You're right of course, but the scale of the Universe serves to explain the sheer wonder of all this to people unused to thinking in these terms. Astro navigation relies, of course, on angular distance not linear., but if one says, do you know that the sun's declination varies though 46 degrees from summer to winter, they'd probably blank you. Mention the in-line distance and we all sit up.

[@jonnypatwilkinson173]

Works on a plane note a globe though, right.

[@iveneverseensuchbehaviorin5367]

doesn't work on a flat earth. go find a flat earther that can explain how celestial navigation works. you cant because there are zero flerfa who know how celestial navigation works.

[@entangledmindcells9359]

Nice try Jonny, So tell us how this is possible. Its all based on Celestial Navigation. Two people on opposite sides of the flat earth with their backs to each other look south and see the same stars. They head further South meaning they are heading away from each other. The same stars they see, get higher in the Sky meaning they are getting closer to the GP. So how can two people heading away from each other can at the same time be getting closer to each other.. I can explain it on a Globe. Can you explain it on your Flat earth?