I'm really surprised to see an instruction about sextant now. It reminds me of my celestian navigation I took at school in the early 70's and our long navigations when we used celestial navigation extensively until 20 + years ago … and then we became stupidly lazy. There is nothing more satisfying to make a right course thanks to celestial navigation, there is no more satisfying thing to know where you are relative to the land / continents and to the celestial bodies… I do miss that a lot (along with the rest of sailing of course…).
@Lelz Rofl Dude ! You made the best response in YT since a very long time. Yes it is 5 000% more interesting than GPS and more … Cheers, Happy New Year and best of luck !…
My father was a master mariner/marine surveyor in the early '70s. I am only now at the age of 64 learning to use this instrument in spite of his eagerness to teach me because in those days motor cycles, horses and girls were far more important. It does give one peace of mind.
Outstanding series Chris. I did a tour on the carrier Carl Vinson CVN-70 in the 1990's. The navigator did his sextant readings daily, morning, noon and evening. I asked him why he bothered since he had GPS etc. His reply was that if there was a war (nuclear), GPS and all of that stuff would be gone and he would be back to navigating with the sextant. Convinced me to learn this skill. Glad I did!
The Communist Chinese have been frequently JAMMING all GPS reception over vast areas of the south China sea and South Pacific ocean! And we're not even at war with these bastards!
Excellent teaching video! Your presentation style is outstanding, the use of video close ups on the micrometer, the use of the laser pointer, and the thought the glass views are all very well done. I wish I had seen this video 26 years ago when I was learning how to use my sextant before a voyage. Your video clearly explains things. Fair winds sailor!
Great video! I've never understood how it was possible to measure such angles to such high resolution while sitting or standing on a moving object. Obvious when you know how. Thank-you!
Hi Chris! I very much like the smooth and veracity of your material. I am in the process of getting my first sextant and I hope some day I could shoot at the stars and put in practice what I have learned. Thank you for your kindness and for sharing your knowledge with others. May the Lord who created the heavens and know all the stars by its own name keep you safe out in the ocean by having always a heavenly body over your vessel.
Being a new Merchant Mariner/Seafarer I am very interested in learning the old school navigation methods and tools. This is very interesting and informative indeed! Thanks for sharing!! 🇺🇸⚓️🌊⛴
A sextant (and any protractor, but with varying degrees of accuracy) can also be used to do a lot of other nifty things. You could, for example, measure the angle between two or more landmarks (usually on the coast), trace the lines/angles on the chart, and triangulate your position.
Several years ago while my wife and I were taking a cruise, we had the opportunity to join a group tour of the bridge. After the Captain finished describing the advanced satellite navigation systems and sophisticated displays, one of our group (sarcastically in my opinion) asked where they kept the sextant. An officer walked over to one of the desks, opened a drawer and pulled out, with a subtle smirk, a sextant and paper map . He never asked another question. It was great to see.
Thank you most sincerely, sir! A fellow boater and friend of mine recently gifted me with a sextant! (I was, like, "A 'sex' what?!)... So, now, very cool! My eternal appreciation for your excellent lesson. Godspeed!
Third video I've watched on the sextant so far and the best. I like how it gets to the basic idea of what you do and what you see etc. I knew nothing about it 10 minutes ago now I got a rough idea. I wanted to research after seeing Robert Redford use one in All is Lost. Next thing I wanna look up is, how do you take those measurements and apply them to a map? I guess there is a video on that also. I will look.
Hi Mark, I know many sextants have removable telescopes (mine included) - however most are not very powerful, only a few times magnification. As far as spyglass with sextant attachment, I can't recall seeing anything like that, but that doesn't mean it doesn't exist!
Nice intro and well spoken for a beginner like myself interested in the likes of David Thompson explorer map maker. Seems though, it would be well to do with having a lanyard for this device especially around water.
Hi Chris, Thanks so much for your video's I have been trying to learn Celestial Navagation on my own for some time using a Davis Mark 25. One question....you reference "notes below" at the end of most of your videos. How does one access those notes? Thanks again, you make this seem more understandable than most.
Thanks Pat, glad to hear it! If you look just a few lines up from this comment, to the "Published on April 5, 2013" section, click on the "show more" button and it should give you all the references. Good luck! - Chris
I was curious how this is done. This is the 3rd and easiest, although not easy, instruction I’ve watched. It is not clear to me after you take this measurement - how do you know where you are?
AlanBoatyman Hi Alan, I do recommend it, however I would say that pretty much any sextant is good enough for the job...if you buy new, great, but if you buy used, just be sure to check the motion of the arm, and also that you can see through the telescope clearly. Plastic sextants are perfectly good as well, especially for starting out...but if you are looking for a lifelong partner, the IIIB is a good investment - good luck!
Hello Prem, I use the altitude intercept method at all times of the day to find lines of position. You need a chronometer (time) to use the method to maximum accuracy. At noon, you don't need the chronometer to calculate a line of latitude from the sun. Hope that helps!
Hello! Usually in rough weather your first concern is bracing yourself somewhere. Then, I usually take the average altitude measurement when I can actually see the horizon over the waves. It is beneficial to take a bunch of measurements and average them for height and time. Thanks!
I am new to this - one wonders whether there is a calculator or similar to give position once angle is found? There is a French computer sextant that seems much safer than looking at the sun through a telescope!
"StarPilot" sells a TI-89 with built in CelNav software. www.starpilotllc.com/ I highly recommend these android apps: "Celestial" by Navimatics play.google.com/store/apps/details?id=com.navimatics.app.celnav "Sight Reduction" by Navigational Algorithms play.google.com/store/apps/details?id=com.Sightreduction "Nautical Astronomy" by Navigational Algorithms play.google.com/store/apps/details?id=com.AstroNavigation "Nautical Almanac" by Navigational Algorithms play.google.com/store/apps/details?id=com.NauticalAlmanac Navigational Algorithms also makes some great free PC software. There are also fomulae in the "explanation" section of the Nautical Almanac which can be used with any calculator and/or spreadsheet/program capable of trig functions.
Hello Toni, Celestaire is the manufacturer and it is also available on Amazon, but don't feel like you have to start with a metal sextant, plastic ones are good too.
Hi Chris, Alidades measure horizontal angles (parallel to the sea) and the sextant can do both horiztonal (if you hold it sideways) and vertical (if you hold it normally). You would use an alidade for taking bearings from objects to plot on a chart or maybe to do some celestial nav when the object is close to the horizon. Thanks!
Though i wonder, you sextant isnt stable it lifted by human which is also rocking. How can you properly measure something which so much things in motion?
That is a good point Rombout, depending on the sea conditions, you sometimes need to average your height between the peaks and troughs of the waves. If you get a chance to look through one, it might clarify your point, for the most part if you assume you use a sextant to navigate on the open sea, an error of a mile or so isn't catastrophic. So a combination of knowing your height (or averaging it) and keeping yourself as steady as possible does the trick. Thanks!
Also as low as possible on the ship than, that means the least amount of motion or rocking. My father had one, but i havent touched that thing in 20 years orso.
Because the two mirrors on the sextant are consistently relative to each other without regard for the movement of the operator, it is actually much more stable than you would think. I can do deep knee bends while taking a shot and the horizon and sun do not jump around but stay right in view in a very stable manner as I screw them down to just touching.
Dude, this is the third video about the sextant I've seen, and it blows the other two to bits. It's some of the same material, but presented in a way that a complete novice (me) understands every concept presented. You're the rare combination of a subject master and an effective teacher -- well done!
Thanks! This is easily the clearest, best presented, and most comprehensible explanation of how to use a sextant that I've ever seen...and at a total length of 7:51, well within the attention span of at least some RU-vid viewers. :-)
Wow, I always thought using a sextant would be crazy complicated... You made this piece of metal that does magic into something logical that actually makes sense.
I was a navigator in the merchant navy before the GPS system. I`ve made thousands of these calculations using HO 211 and HO 249. The stars in the morning and the evning made the best fix. Six or seven stars within five minuts. I did`nt like when the D.R. became older than 24 hours because of overcast. Navigating through The Red Sea was horrible because of extensive refraction. You could not thrust the horizon like you can not thrust anything else in that eryea.
hans klint: Noticed your comment that cites two sources, 1-HO 211 and HO 249, for determining calculations. Why use two different methods ? Is one more accurate or faster ?
hans klint I'm Portuguese and my uncle works as a first year professor at the Lisbon school of navigation but is from the Azores. I try using their facts to prove a globe (flat earthers) but they don't listen. They only use aviation not maritime navigation.
Roger Baker - Sorry to have to correct you - but Level is NOT the same as Flat. Level is a plane at right angles to a line from your position to the centre of the Earth. Flat means there is no hollows or humps. Look up your dictionary. Celestial Navigation DOES use SPHERICAL TRIGONOMETRY math to calculate a position line - so where you get the idea spherical trig has no practical application suggests you have never done an ocean passage where you are out of sight of land for days on end - never used a sextant and never done the calculations for yourself - never plotted a Celestial Sight calculation on a chart. I have sailed about 5000 nautical miles on offshore passages - some legs more than 1000 nautical miles like Auckland to Savu Savu, Fiji - and Auckland to Nukulofa, Tonga a couple of times in small yachts.
Excellent videos, by far the best I've found in the web (and I've seen quite a few). One question about the noon sight... I'm doing fairly well on latitude but my longitude is consistently off by 20+ miles. I've read the challenge is that the sun's path flattens near the top of the arc so it's hard to tell accurately exactly when it occurs. I've read that this is an inherent limitation of this technique and that even "shooting the arc" (before and after local noon, and averaging to find the midpoint) is not very accurate. Is this true and if so, can you explain why shooting the arc is not so accurate (it seems mathematically sound)? And thanks again for the videos.
Chris Doubleday Hi Chris, great questions. Congratulations on the noon latitude sights, I'm happy you are having success! Everything you said is true - longitude at noon is possible, but a bit hard. The strategy is mathematically sound: in broad strokes what you need to do is measure the sun a bit before noon and note the sextant reading and exact (and I mean exact) time. Let the sun go up, then down again. When it reaches the exact (again, I mean exact :)) height as before, note the exact time. Average the times and you have the exact time of meridian passage. The reason for exactness is the sun moves "over" the surface of the earth at about 1 mile every four seconds...so you need to be precise. Once you know the exact time, calculate how many hours, minutes, and seconds you are late on Greenwhich time...convert that time to arc (using the nautical almanac 'conversion of arc to time') and you should be about as close as you can get. Watch for common errors in math, make sure watch is synched to correct time, and also be careful with time zones and daylight saving time. Just personally, if I were to rank order the steps I would want to learn celestial navigation, I would put longitude at noon towards the end...it is a more complex topic. Another cool trick you can do for longitude is use the horizon as a sextant...around sunrise and sunset, the sextant height would be zero...no sextant required. There are a bunch more corrections for atmospheric refraction, though. But it should give you a longitude line. All that said, for primary means of determining longitude, I recommend doing morning and afternoon lines of position (later videos in the series) and then getting a running fix (or use multiple bodies like a sun/moon fix). Hope that helps and good luck! - Chris
Nice video. I am going to to learn this. It got me thinking how the sentiment these days is that we've left the entire past in the dust with the computer age. I can rarely get someone under 35 or so to be interested in anything not "techy". But can you imagine the minds the developed a technology like this. If I understand correctly it is accurate to within 1nm. The first sextant dates to around 1759. what is that, 264 years? I find that just amazing. No batteries or connection required. A beautiful, to me, tool and a book. And a brain.
Nice video. I am going to to learn this. It got me thinking how the sentiment these days is that we've left the entire past in the dust with the computer age. I can rarely get someone under 35 or so to be interested in anything not "techy". But can you imagine the minds the developed a technology like this. If I understand correctly it is accurate to within 1nm. The first sextant dates to around 1759. what is that, 264 years? I find that just amazing. No batteries or connection required. A beautiful, to me, tool and a book. And a brain.
Hey thanks! I actually learned how to get bearing from a Croatian Navy navigator a few years ago, he was so nice and our families bonded over the internet. He died right before covid unexpectedly, have been sad about it for a long time. So videos like this mean alot to me on another level. I built my own device to get angle since I could not afford a good sextant and was able to go thru the calculations for good practice. This video took the mystery out of how the device works, super appreciate it!
Start with this tutorial , I just watched four others made by unprepared babbling and stuttering showoff's who for same reason decide to waste everyone's time .
The sextant has two mirrors and the two images of the sun and horizon are somewhat mutually compensated. It's easier than you might imagine, the problem is holding on without both hands being free!
Level follows the curvature of the earth. Celestial navigation is created with the earth being a sphere. Celestial navigation wouldnt work if the eath was flat. Celestial navigation works, therefore the earth is a sphere. Your comment is meaningless, but if you want to understand the error of your ways i can help you.
'...a lot of straight lines...' Only two. The curved line to the horizon, the dip correction takes care of that and the curved line to the celestial body that is being observed. The altitude correction takes care of that. None of you 'tards can demonstrate celestial navigation on a notional flat earth. Why is that?
What a godsend of tuition. Also, what a piece of kit. I'd assume that captain Bligh's sextant was a little more primative than this piece of cutting edge technology 🤔
I have finished watching this video completely. (我看完這部影片了) I am a Taiwanese who cares about the global affairs. (我是一個關心全球事務的台灣人) And, sadly, most of my fellow Taiwanese don't really care about the world. (但是，很不幸地，我大部分的台灣同胞不那麼在意世界。) Hopefully Taiwan can become increasingly globally-aware and globally-competitive. (希望台灣可以越來越有全球意識與全球競爭力。) God bless Taiwan. (天佑台灣。)
Really enjoying your videos and the illustrations are helpful. I am a toolmaker so I need to use trig a fair amount, so celestial is becoming more clear to me. Already purchased a slightly used Weems and Plath sextant. Now for my next sailboat. You cant spend all your time working!
Ryan B My reply to Charles is that all is lost is the worst movie I have ever seen demonstrated absolutely no sea knowledge or boating knowledge whatsoever
Another sextant video said that this is the reason sailors centuries ago had eye patches, because they burned their eyes using sextants. I guess the irony is, if you have no eyes, you don't really care where you are. Time for pirate rum and let someone else figure it out.
If you found this interesting, you can buy a very basic sextant for less than $50: the Davis Mk 3, which is a plastic version of the WWII lifeboat sextant. There are also patterns available on the Web for making your own sextant out of wood or cardboard. (Probably for using a 3D printer, too, but I haven't researched that.) It's fun to actually put the skills shown to use; better than just reading/watching about them.
when I was in the Navy we were transiting from the Panama Canal to San Diego. We lost our Loran and couldn't get a good idea where we were. We surfaced and our Navigator went to the bridge shot the stars and got our position. Once they fixed our navigation systems it was determined he was correct within 100 yards. Not bad!
Hi, I'm new to navigating. Can you explain how in 2:39 is it 31'40" (31.4'?)? I'm confused as to what line I should be reading from. Is it because the decimals "start" just after the first short line after 30' and the .4 matches a line? Thanks!
excellant video, eager to watch them all. Thank you for taking the time, and providing great teaching/film skills. Is there a Sextant you recommend? We have not purchased one yet. Should we start with a plastic one to learn on, or just save up for a nicer one?
Hi Michelle, thanks! If you are fitting out a boat, as much as I enjoy celestial nav, I would probably recommend getting an inexpensive sextant to start with…in my opinion there are lots of higher priority places to spend money on a boat like food or lifejackets. If you are buying used, just be sure the arm swings smoothly without binding, that the telescope is clear, and that if you set the sextant to 0 degrees, 0 minutes, distant objects are fairly "together." If there is a huge jagged edge in the image (reference "index error" on wikipedia or in the video), the sextant needs calibration and will be a pain in the butt for you over time. Basically you want to be able to clearly see the sun and the horizon for practice. The other benefit to an inexpensive sextant is that in an emergency, it will do the job just fine (noon sights and such), and honestly, that's why we carry one anyway. You can always upgrade later if it proves to be an enjoyable hobby. Good luck!
NavigationTraining Whoa, sorry, I like the vid and what you're doing, but I have to comment on the quality of the sextant. I've worked with astro-nav since I went to sea in 1977, and my experience of cheap sextants is that the results are mediocre, and that discourages learners. 'Cheap' usually means 'plastic', and those things are not consistent... sure, you can navigate with them, but significant errors result from environmental changes, and you need a profound knowledge of sextant errors and a lot of attention to get consistent results. As I have often said, you need to be a very good navigator to use a plastic 'sun-gun'! Now, once you get to the metal sextants, then I agree with you; there's not such an issue and in terms of quality an economy Zeiss or Chinese model will probably serve a beginner as well as a top-end Plath... but again I'd add that, for small-boat astro-nav, one of the most critical factors for a beginner is the stability of the sextant, which means you want something fairly heavy. This damps out motion and reduces shake in the optics from wind, sea, engine vibration, etc. The cheaper models, like Tamaya, Astra, Zeiss weigh about 2lb; my Cooke-Kingston weighs just over 4lb, and a Plath about the same... and these are much steadier, and thus easier for a beginner to get the accurate readings which will translate to sharper navigation and thus encourage further learning. And finally... yes, I am the Old Man Of The Sea, but not all harking-back is unwarranted. Astro-nav is not quite only a hobby yet. We live in very uncertain times, and GPS or GLONASS can easily be switched off or coded. The time will come when astro-nav is merely a historical interest, but it is not yet! Anyway, have fun!
On land where the horizon is hard to decipher like in the mountains...........a puddle or container rolled with water can be used. You can make a very basic version of this sextant with string and a semi circle with degrees written on the convex side. Aim the flat line at the celestial body and the string will stop at the correct angle with a weight on the end. It can be done in many ways without a sextant and is still very accurate except in rough seas but then a extant isn't that great on a rough sea.
how Automatic astrotrackers such as, MD-1 Automatic Astro navigation system, work? how it know about which star it measuring (without image processing)?
Thanks for the Fantastic video. Can this method be used at land? Mountains etc can interfere and make false readings was my thought,can it be used on mountain ranges or flat desert?? And it seems quality is very important as you don't want to get blind by the sun.
Hi Chris, Just found your videos and Santa gave me a Davis 25 for Christmas and am now keen on learning how to use it. Very good and easily digestible sound bites. I have a question for you. When taking the sight and bringing the view down how do you know when you are parallel to the surface of the sea? Is this not a potential error if just slightly out? Hope this makes sense. Mike
Hi Mike, good question. When the sun is on the horizon, rock the sextant back and forth so that the sun appears to make an arc, just touching the horizon at the bottom of the arc. almost like a pirate ship ride at the amusement park. If you record the measurement at the lowest point, you know you are parallel to the horizon and that is maximum accuracy. Hope that helps!
Oh yeh. Same reaction here. Navy instructor did a terrible job of explaining celestial navigation (particularly spherical globe). I had to drop the program for a year and when I got back in I had to accept a one year longer contract. But in the end I did really enjoy the time.
'He invites anyone near the sea, and above all on a boat to turn away from their screens & look around.’ David Barrie's #sextant The Halli Casser-Jayne show 5/28 3 pm ET bit.ly/WtMJzD
