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.
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.
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!
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!
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 UA-cam viewers. :-)
Went through about seven other videos on the sextant in attempts to try and teach my sons. Most videos taught vocally using just words and maybe a few complicated drawings. Was losing my sons interest when they kept asking what they meant by bring the sun down to the horizon. Your video not only explained everything, but you showed my sons the actual image of what they would see through the sextant sighting glass as well as the micro adjustments. Your video was greatly superior to other teaching videos in regards to budding young sailors. I smiled when they got that "Oh! That's what it's supposed to look like" look on their face and went straight to their sextants to get the same image. Watching their arms rock back and forth and coming back to your video for reference told me this is the video to bookmark and save. Thank you so much for a wonderful teaching video.
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.
As a new Merchant Mariner/Seafarer I love videos like this that teach the traditional ways of navigation and the old tools like the sextant! Thanks so much for sharing! This is very interesting and informative! I want me one now! 🇺🇸⚓️🌊⛴
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.
I was a USAF RC-135 navigator back in the 80-90s. We used to shoot cell every 20 mintes for up to 12 hours on a flight going 450 kts. Works pretty well in a stable platform if you do your calculations and plotting correctly. Thanks for sharing.
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.
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!
Excellent presentation Chris. I taught day and night time navigation in the Army. We used lensatic compasses and maps but shot angles to landmarks. We had little training on celestial nav except the location of Polaris. (TN) My cousin is the navigator I really admire. He shot stars in the P-3 Orion. (What a name huh?) He was in the Navy back in the late 60's, early 70's. I admire those who can navigate the great oceans and bodies of water her on this earth. I'll be joining you on future lessons. Anchors Aweigh!
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.
My dad flew for the Army Air Force and the USAF for some 33 years starting in ‘36. He taught navigation, communication and was a whiz at keying Morse code right up to when he died. He said the stars were a superior reference. I don’t know that he ever used a sextant but he would have loved playing with one of he had had a chance.
Kim Horton : yes of course he used a sextant to navigate with, from the Navigators bubble canopy atop the larger Aircraft, transports and bombers. He also used Radio directional antennas to fix location and course. What a wealth of information, and history, he had !
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.
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!
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!! 🇺🇸⚓️🌊⛴
I've always been a pasionate for astronomy and naval history, the only thing I never ever touched in my lectures is how to navigate. Such a nice tutorial!! :D
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!
Excellent explanation of reading the Vernier Will. This is something I've never felt comfortable with until this point and that explanation made it crystal clear very well done video
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!
Hi Chris, We are a homeschoolin' family and just read "Carry On Mr. Bowditch" by Jean Lee Latham. I wanted to learn more about reading a sexton and found your YT. You are a modern day Nathaniel Bowditch! It is children's literature but an excellent book to read-consider it. Thank you.
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.
Chris, I have to say that I have reviewed a lot of videos about Celestial Navigation and yours by far are the most comprehensive ones out there. Your teaching methods and video techniques have exceeded my expectations. If you have a moment I would like your thoughts on a question I have about the possibility of eye injury risks involved with using a Sextant. Do you think the constant use of taking shots with the proper shades in place could cause short term or longer term eye injuries. Even with all of the shades in place I am not sure what damage is being done to the eyes looking at the sun on a continual basis. I would like to purchase a Davis Mark 25 but the only thing holding me back are the risks associated with possible eye injury. Thank you very much for your videos and time.
Hi Flying, sure thing - the sextant shades are of similar quality to what welders or astronomers use for their work. If you use the appropriate amount of shades you should have no problem. Thanks!
@@NavigationTraining Chris. Thank you very much for the information. I greatly appreciate it. I have learned so much from your videos and the information on your website. Thank you so much for sharing your knowledge and experience with us.
Great video thank you! Can you please explain how they navigate at the South Pole, back in the day how did they found exact location of the south pole! Thank you!
Using the star, a sextant and a bowl of water (or mercury) like they did on the Lewis and Clark expedition in 1803 . Not as easy as at the North Pole with Polaris almost overhead.
I love your style of teaching. I always wanted to learn how to use a sextant and ive been looking at so many different videos but they just confused the hell out of me and didn’t give me an idea of what to look for. This gave me way too much confidence that I’m ready to go right now 😅 even though idk the equations or anything lmao I’m just excited I finally know what to look for an how to work it and what each dial means lol
It makes sense as explained. Question: How does one determine their position when he does not know the date or time? If one started with a sundial and a compass, he might be able to establish local time, but not a NIST-defined time zone to correct to GMT.
Hello Jack, a great reference for you is "Emergency Navigation" by David Burch, in which they describe how to navigate with what you've got. For example if you have time but no sextant, or sextant but no time etc. But to answer your specific question, you can get an approximate latitude if you at least know the season but not the date. The methods described in the video series date from about the mid 1700s to present and navigators would keep careful track of their past positions (date, time, course, speed, etc.). As far as an emergency tool, generally if you were thrust in an emergency like that you would at least know the approximate date and position - and hopefully you have the tables to go with it!
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
Very engaging presentation. You sir are a talented teacher, not to mention, I am sure, a capable sailer & skipper. A very relaxed, easy to understand presentation style! Obviously, I have a history with teaching in various environments. Teaching is like sailing, some talent is good, but more importantly is a lot of practice & commitment to quality results. Good Job!
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.
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!
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?
Thank you for watching. Part 3 and 4 should be posted by May 5th. I highly recommend the program called Lapware. It costs $100 per month - so use it wisely, but it has every type of problem you could be asked, and allows you to take practice exams. Most people take a course for celestial - depending on your timeline I will have a few more training resources available in the next 2 months that I can pass along. Thanks again!
Odd although I have not searched or spoken of Martinique in the presence of any of my devices it has been on my mind for the past week because of an old movie that came to mind. You're talking about something outward a refresher on. Some people call it Serendipity some people call it Kismet. I'm just happy that it came up.
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.
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.
Great video, couple of points missed. As the sextant is a very accurate instrument, it also needs to be allowed to warmed up to ambient temp prior to use as metals expand and contract, giving you a error. Also prior to use you must check the sextants index error, this is done by having the sextant at zero, no shades, and compare the difference in horizon. If error is small you can move the vernier and note the difference. This will be applied during the calculations. If the difference is too large. More than a degree. Then you need to adjust your mirrors before using
Hi Cole, this is done to make sure that you aren't looking at the sun in a cockeyed position. It helps make sure that everything is lined up correctly. For instance if you hold the sextant slightly tilted, the sun appears to rise or set. Swinging just makes sure it is as accurate as possible. Thanks!
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
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 🤔
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 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 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!
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.
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!
1. Could you average out the upper and lower limb of the sun to get an exact middle? 2. Is minute of arc the same as minute of angle? I'm not really a gun expert but I have heard this term before.
Hi Peter, the semi-diamter of the sun is about 30 arc minutes. It's apparent "thickness" changes a bit over time/season. So you're really better off shooting the lower or upper limb and applying the correction. See later videos in the series for more on that. It looks like Aaron covered the second question, thanks Aaron!
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.
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!
Hi,Chris,best regards from Bulgaria,from a future Navigator. Great movies great knowledge,everything perfect!!! I would like to ask about the sextant you are using in those videos.What Celestaire model exactly it is?...as I am planning on buying one of these.Is it the Astra III with Trad mirror or the one with WH mirror? Love Celestial navigation. Thank you in advance ,take care. Rosen
Hi Rosen, thanks for writing. This particular sextant is the traditional split mirror. If you get a chance to use a whole horizon mirror, many people like them better. However anything will do the job. Good luck! - Chris
I do appreciate your answer, Chris. Once I bought it,I will send a photo !......can't wait. Thanks again for answering,and I wish 7 foot under the keel,and God Bless!
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 !…
Lelz Rofl it’s wild how some of us are drawn to the sea... and then boring people like you are scared of water
@@stuarthiggerson5846 Your response is so predictable : who's boring ?
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.
Thumbs up.
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.
Every Captain worth their salt would have one on their ship. Early Boeing 747 even had a sextant.
man your way of explaining is so simple and up to point even a small child will grasp this easily ..much blessing to you mate ..
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!
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!
Grandpa Jones
Better to have and not need then need and not have
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!
@@pemaangya5830 Pema Angya
Grandpa Jones
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!
Thanks for the kind words, all the best to you.
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 for the kind words Dave, enjoy your journey in celestial navigation!
Spot on mate
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 UA-cam viewers. :-)
Went through about seven other videos on the sextant in attempts to try and teach my sons. Most videos taught vocally using just words and maybe a few complicated drawings. Was losing my sons interest when they kept asking what they meant by bring the sun down to the horizon. Your video not only explained everything, but you showed my sons the actual image of what they would see through the sextant sighting glass as well as the micro adjustments. Your video was greatly superior to other teaching videos in regards to budding young sailors. I smiled when they got that "Oh! That's what it's supposed to look like" look on their face and went straight to their sextants to get the same image. Watching their arms rock back and forth and coming back to your video for reference told me this is the video to bookmark and save. Thank you so much for a wonderful teaching video.
Thanks for the kind words, good luck!
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.
Thank you for watching and for the feedback. I hope future episodes are useful!
As a new Merchant Mariner/Seafarer I love videos like this that teach the traditional ways of navigation and the old tools like the sextant! Thanks so much for sharing! This is very interesting and informative! I want me one now! 🇺🇸⚓️🌊⛴
Glad it was helpful!
Hi sir
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.
An excellent video for learning the basics of a sextant. The setting gave me chills from great memories!
Glad you enjoyed it!
I was a USAF RC-135 navigator back in the 80-90s. We used to shoot cell every 20 mintes for up to 12 hours on a flight going 450 kts. Works pretty well in a stable platform if you do your calculations and plotting correctly. Thanks for sharing.
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.
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!
I would like to thank you for the videos...I am sitting for Exams and I found them very helpful. All the best to you. Thank you again
I showed this to my kids today. We are studying inventions and the compass and sextant. Very interesting video. Thank you.
Excellent presentation Chris. I taught day and night time navigation in the Army. We used lensatic compasses and maps but shot angles to landmarks. We had little training on celestial nav except the location of Polaris. (TN) My cousin is the navigator I really admire. He shot stars in the P-3 Orion. (What a name huh?) He was in the Navy back in the late 60's, early 70's. I admire those who can navigate the great oceans and bodies of water her on this earth. I'll be joining you on future lessons. Anchors Aweigh!
Sir, I am a nautical science student and its for the first time I am understanding how to use sextant.. well taught sir
Great, well thought out video. The dual view shots during adjustment are perfect. Thanks!
Glad it was helpful!
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.
Thanks Hans, I can imagine the Red Sea must have been a difficult place to navigate! Thanks for sharing your story!
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.
+Larry Medina
Actually Flat earthers will deny even the very nose on their face if they think it's being used to prove them wrong.
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.
My dad flew for the Army Air Force and the USAF for some 33 years starting in ‘36. He taught navigation, communication and was a whiz at keying Morse code right up to when he died. He said the stars were a superior reference. I don’t know that he ever used a sextant but he would have loved playing with one of he had had a chance.
Kim Horton : yes of course he used a sextant to navigate with, from the Navigators bubble canopy atop the larger Aircraft, transports and bombers. He also used Radio directional antennas to fix location and course. What a wealth of information, and history, he had !
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.
Very Good Video for beginners to try and take hold of this most difficult subject, Thanks!
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!
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!! 🇺🇸⚓️🌊⛴
If you are shooting a sighting in the hood, do you hold the sextant sideways?
LOL. That's a crappy way to hold a pistol too.
Too funny...
lolz
Only a gangsta pirate would do navigate the high seas that way!
Of(f) course.
I've always been a pasionate for astronomy and naval history, the only thing I never ever touched in my lectures is how to navigate. Such a nice tutorial!! :D
Thank you for sharing your knowledge, very much appreciated. You are a good teacher.
Very well explained, all that we need now is the formula to get the answer that we are looking for, thanks.
Hi thank you Alan, the next videos in the series start to talk about the formulae for the process, thank you!
Thanks for watching, I wish you good luck in your learning!
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!
Excellent explanation of reading the Vernier Will. This is something I've never felt comfortable with until this point and that explanation made it crystal clear very well done video
Thanks for the video I'm not a navigation person but have always been interested in sextants. I understand how useful they can be.👍👍👍
a well spoken young man and very good presentation
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!
Quick, clear, simple. Well informed video.
Excellent...clear and concise. Oh, to be in the summer sun again. It's the middle of February here in New Jersey.
Just found these videos. You're a very good instructor - thank you for making these!
Do the flame stickers on your sextant make your boat go faster?
Chief, Indeed, I have the fastest sextant on the seven seas. It gives my students a laugh when I open the box after much drama :)
Hi Chris, We are a homeschoolin' family and just read "Carry On Mr. Bowditch" by Jean Lee Latham. I wanted to learn more about reading a sexton and found your YT. You are a modern day Nathaniel Bowditch! It is children's literature but an excellent book to read-consider it. Thank you.
Outstanding work, Christopher!
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.
Chris, I have to say that I have reviewed a lot of videos about Celestial Navigation and yours by far are the most comprehensive ones out there. Your teaching methods and video techniques have exceeded my expectations. If you have a moment I would like your thoughts on a question I have about the possibility of eye injury risks involved with using a Sextant. Do you think the constant use of taking shots with the proper shades in place could cause short term or longer term eye injuries. Even with all of the shades in place I am not sure what damage is being done to the eyes looking at the sun on a continual basis. I would like to purchase a Davis Mark 25 but the only thing holding me back are the risks associated with possible eye injury. Thank you very much for your videos and time.
Hi Flying, sure thing - the sextant shades are of similar quality to what welders or astronomers use for their work. If you use the appropriate amount of shades you should have no problem. Thanks!
@@NavigationTraining Chris. Thank you very much for the information. I greatly appreciate it. I have learned so much from your videos and the information on your website. Thank you so much for sharing your knowledge and experience with us.
Great video thank you! Can you please explain how they navigate at the South Pole, back in the day how did they found exact location of the south pole! Thank you!
Using the star, a sextant and a bowl of water (or mercury) like they did on the Lewis and Clark expedition in 1803 . Not as easy as at the North Pole with Polaris almost overhead.
Hi. Great video. nicely pitched ...not too in depth but very informative. I'll be checking out your other vids and thanks for posting...
Thanks! Yep it's a Astra 3B. The flame job is custom :)
I love your style of teaching. I always wanted to learn how to use a sextant and ive been looking at so many different videos but they just confused the hell out of me and didn’t give me an idea of what to look for. This gave me way too much confidence that I’m ready to go right now 😅 even though idk the equations or anything lmao I’m just excited I finally know what to look for an how to work it and what each dial means lol
You are so welcome!
It makes sense as explained.
Question: How does one determine their position when he does not know the date or time? If one started with a sundial and a compass, he might be able to establish local time, but not a NIST-defined time zone to correct to GMT.
Hello Jack, a great reference for you is "Emergency Navigation" by David Burch, in which they describe how to navigate with what you've got. For example if you have time but no sextant, or sextant but no time etc. But to answer your specific question, you can get an approximate latitude if you at least know the season but not the date. The methods described in the video series date from about the mid 1700s to present and navigators would keep careful track of their past positions (date, time, course, speed, etc.). As far as an emergency tool, generally if you were thrust in an emergency like that you would at least know the approximate date and position - and hopefully you have the tables to go with it!
@@NavigationTraining I really appreciate your response. I will check out the reference you provided.
i would like to see you do a video showing how to practice taking sites with an artificial horizon
Sex
Great tutorial and facinated to know how this device (sextant) works. (thanks)
Does it matter to you if you use a split horizon or a full horizon sextant ?
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
What kind of sextant is that ? I want one that is not a Davis plastic sextant. I like your style of explanation , thorough and fast
This is an Astra IIIB, thanks for watching!
You have produced excellent videos. It would be nice to add, how to calibrate a sextant, (the mirrors) before taking a shot.
Thanks for the feedback, I'll look at that topic for the next video series in the spring. Thanks again!
Great explanation. Thanks for all the links to resources.
But how far are u away from the "horizon" ? I dont understand this. What exactly are u trying to measure with the sextant.
The sextant measures the angle from the horizon to the star.
Very engaging presentation. You sir are a talented teacher, not to mention, I am sure, a capable sailer & skipper. A very relaxed, easy to understand presentation style! Obviously, I have a history with teaching in various environments. Teaching is like sailing, some talent is good, but more importantly is a lot of practice & commitment to quality results. Good Job!
Thanks for the videos What model sextant is yours?
Excellent. Thanks. Always been interested in this. Thanks for explaining so well.
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.
The technique works on land if you use an artificial horizon and make some adjustments. Thanks!
How in the world can you take these measurements WHILE YOU ARE ROCKING ON A BOAT?!
How did / do sailors on the open ocean do it?
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!
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?
Just starting to learn and this video is excellent and so well presented.
Thank you extremely helpful and informative
Thank you for watching. Part 3 and 4 should be posted by May 5th. I highly recommend the program called Lapware. It costs $100 per month - so use it wisely, but it has every type of problem you could be asked, and allows you to take practice exams. Most people take a course for celestial - depending on your timeline I will have a few more training resources available in the next 2 months that I can pass along. Thanks again!
Odd although I have not searched or spoken of Martinique in the presence of any of my devices it has been on my mind for the past week because of an old movie that came to mind. You're talking about something outward a refresher on. Some people call it Serendipity some people call it Kismet. I'm just happy that it came up.
that was great...first time I've ever looked at a sextant..better late than never...
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.
Brilliant! I am just doing a course on Celestial Navigation, and this is a wonderful explanation on how to take the measurement. Thanks heaps :)
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!
Damn, I wish I had you as my celestial navigation instructor in the navy. " Rock the sun"
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.
Great video, couple of points missed. As the sextant is a very accurate instrument, it also needs to be allowed to warmed up to ambient temp prior to use as metals expand and contract, giving you a error. Also prior to use you must check the sextants index error, this is done by having the sextant at zero, no shades, and compare the difference in horizon. If error is small you can move the vernier and note the difference. This will be applied during the calculations. If the difference is too large. More than a degree. Then you need to adjust your mirrors before using
Hello Aaren, thanks for the comments, this video is the first of an 11-part series, and those concepts are covered later. Thank you! -Chris
Thank you Chris. Great work
Excellent tutorial and links. Keep up the good work!!!
Great video! What is the reasoning for swinging the sextant and making sure the sun forms an arc with the bottom touching the horizon?
Hi Cole, this is done to make sure that you aren't looking at the sun in a cockeyed position. It helps make sure that everything is lined up correctly. For instance if you hold the sextant slightly tilted, the sun appears to rise or set. Swinging just makes sure it is as accurate as possible. Thanks!
Nice learning with you, I have one and studying trigonometria
How does the second matter when it takes several seconds from when you are done with the reading and have written it down after looking at your watch?
You look at your watch first. The reading stays on the sextant if you don't move the arm.
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
How did I get here?
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 🤔
Could u explain y we prefer long by chron in morning and intercept in evening?
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!
great vid and gorgeous gorgeous footage.
Hi my friend, where can to buy any sextant like this? Link store ? Thank you!
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.
@@NavigationTraining thank you!
Take care!
Where can I get a sextant like the one you are using in your video? I am enjoying your videos.
Excellent video. Thank you
This is great, very instructive and well presented. I like how you start simple, with basic concepts, and add layers of accuracy and detail later.
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!
*Astra III Professional Sextant* - ISS just got one for testing deep space navigation.
Where can I buy one?
Text256
Then 404
85.
Seventy nine
Ive got a Tamaya Jupiter MS 833.
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.
What an awesome explanation. Keep pumping out these videos. Great job man.
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!
Wow! Thank you for the info!
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!
1. Could you average out the upper and lower limb of the sun to get an exact middle?
2. Is minute of arc the same as minute of angle? I'm not really a gun expert but I have heard this term before.
A minute of arc is one 60th of a degree
Hi Peter, the semi-diamter of the sun is about 30 arc minutes. It's apparent "thickness" changes a bit over time/season. So you're really better off shooting the lower or upper limb and applying the correction. See later videos in the series for more on that. It looks like Aaron covered the second question, thanks Aaron!
Thanks Aaron, yes indeed.
are you using an Astra 3B? btw, i like the flames!
loving this series. where are the notes though
Hi Jane, they are just below the video in the UA-cam screen. They contain some links of interest. Thanks!
Hi Jane, if you click on the area in UA-cam just below the video, there are a bunch of links and notes about the video. Good luck!
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.
Chris has a video where he demonstrates the process of converting an observed altitude into an intercept.
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!
Hi,Chris,best regards from Bulgaria,from a future Navigator. Great movies great knowledge,everything perfect!!!
I would like to ask about the sextant you are using in those videos.What Celestaire model exactly it is?...as I am planning on buying one of these.Is it the Astra III with Trad mirror or the one with WH mirror? Love Celestial navigation. Thank you in advance ,take care. Rosen
Hi Rosen, thanks for writing. This particular sextant is the traditional split mirror. If you get a chance to use a whole horizon mirror, many people like them better. However anything will do the job. Good luck! - Chris
I do appreciate your answer, Chris.
Once I bought it,I will send a photo !......can't wait.
Thanks again for answering,and I wish 7 foot under the keel,and God Bless!
Dude's got flames on his sextant. Freakin' LEGEND!!!!!!!!!!!!