This video deserves a 'part B' where you work through an actual example. Good work on part A, best description I've found so far.
@roohif2 жыл бұрын
The line you draw from the observer to the GP of the star at 4:53 is *INCORRECT.* The line of sight between the observer and the star, and the line between the GP and the star are *PARALLEL* - it's not a triangle. The reason you see the star at 50 degrees elevation is because you are 40 degrees of a sphere away from the GP of the star. At 69 miles per degree, that makes the distance to the GP equal to 2760 miles.
@sleepingwarrior46182 жыл бұрын
Roohif, is that line of sight a straight line? Or is it subjected to 7/6r? It's subjected to 7/6r isn't it.....so that means to can't get a 90° anywhere as well.....funny looking triangle that.
@golfkilo62272 жыл бұрын
@@sleepingwarrior4618 There is no need for a triangle, actually.
@roohif2 жыл бұрын
@@sleepingwarrior4618 The line of sight is curved in reality. The whole idea behind 7/6r is to make it straight so the geometry is easier, you frikkin numpty. Watch my recent JTolan video and you’ll see how it works.
@marcg16862 ай бұрын
@@sleepingwarrior4618 The line of sight is refracted, hence the altitude correction table in the Nautical Almanac.
@edshannon44268 жыл бұрын
Kudos to you sir! Most explanations of this process bury the pupil in jargon without first giving a simple conceptual explanation. I for one, thank you very much.
@johnlbales27737 жыл бұрын
Ed Shannon Agree 100%. Thank you. Great job.
@castaway12310010 жыл бұрын
Thanks! This is the best overview I've seen so far. I watched a few other videos that went into great detail, but, they NEVER illustrated what those details were accomplishing. The drawing and simple explanation create context for the detailed math involved.
@DD-lr6ne5 жыл бұрын
Acreedores, excelente descripción
@raymondlowry85644 жыл бұрын
I was also in the Navy ( in the early ‘70’s) as a Quartermaster. Your presentation brought back some fond memories, for instance how satisfied we would get achieving a pinwheel fix when shooting stars. Not always easy when your vessel is rolling and pitching. I wonder if ships still carry Chronometers? In any case, nice job Sir.
@TNEWHAT2 жыл бұрын
Negative, am a quartermaster currently and mostly everything is based on VMS better known as electronic navigation.
@DivergentDroid Жыл бұрын
You claim: " The thing is, it is very easy to prove that cel nav requires the globe. The single fact that no flat earther has ever accomplished cel nav without the globe is proof." - NO Not gonna cut it son! You just used a strawman fallacy which is also begging the question to back your claim instead of actual evidence. I'm sure you meant it as a red herring too! 3 fallacies! Look them up son. Show me you taking an elevation angle without a straight horizontal baseline. You Cannot do it!
@robertlafleur51795 ай бұрын
@@DivergentDroid_’’No flat earther has ever accomplished cel nav without the globe…’’_ I’m sure you won’t let this be and will do a Flat Earth CN demonstration right now, right? I wonder why no flat earther has ever done it? Don’t tell me that Earth being a globe is stopping you. When has facts ever stopped a flerf making a fool of himself?
@MyNameIsNobody579 жыл бұрын
In case anyone is wondering what "H0229" is, it's a Nautical Almanac. "A nautical almanac is a publication describing the positions of a selection of celestial bodies for the purpose of enabling navigators to use celestial navigation to determine the position of their ship while at sea. Wikipedia"
@albertsarigumba47066 жыл бұрын
Table 249 not, HO 229 Sir!!!..
@seankivler19576 жыл бұрын
By the previous comments in response to your 'H0229', Its' a wonder any of you found your way back to shore!... So, dare I ask this 'confused' bunch, how this differs from an Ephemeris?...
@seikibrian86416 жыл бұрын
Sean Kivler -- There are many ephemerides, with different formats and layouts. H.O. 229 and H.O. 249 are particular publications designed specifically for navigation.
@tortillafilms6 жыл бұрын
Those Manuals ,are correct : 229 & 249 Sight reduction Tables/air nav.
@TheHarshRealm5 жыл бұрын
229 is sight reduction tables. The air, or nautical almanac is a book reproduced yearly. I have a set of 229 onboard that was printed in the 70’s and they are still correct.
@davecorley55144 ай бұрын
Good first-order explanation. Fifty three years ago I took two, three-hour classes on navigation over two semesters. One semester was devoted to celestial navigation. It was a part of my training as a midshipman at the US Naval Academy. Forty years ago, I served as Navigator on two nuclear submarines. To take celestial observations, we had to attach a specialized sextant to the bottom of our periscope and be at periscope depth for the duration of the observation at nearly constant course and speed. The fixes we obtained were usually very inaccurate when compared to modern electronic navigation fixes - errors of +/- 5 miles or more were common. Modern gps fixes with errors less than six feet are quicker and don’t require extended time at periscope depth. But, we’d take celestial fixes through the scope every year just to stay in practice. An operational difficulty for submarines is that celestial fixes are best taken near twilight (near sunrise or sunset) to be able to view both stars/moon and horizon at the same time. That meant that bad guys would know when a sub had to be at periscope depth to take these observations. Not good. So, we avoided celestial navigation in favor of electronic navigation fixes - GPS, NAVSAT, LORAN-C, OMEGA, bottom contour fixes. We also had two inertial navigation systems that maintained estimated position of the sub using gyroscopes and accelerometers. The more accurate explanation is that the LOP of a celestial observation represents the intersection of a cone extending from the star towards the earth that intersects with the surface of the ocean’s surface. In the open ocean that intersection describes a circle. And that circle is the LOP. Observation of the altitude of at least two other celestial objects, corrected to the time of the first observation, yields two more circular lines of position. With no measurement or instrument errors, these three LOPs intersect at a point on the ocean’s surface. The point is the fix position at the time of the first observation. Because the surface of the ocean is spherical, then linear geometry will not yield an accurate enough fix. Instead, spherical geometry is used to generate the tables in H. O. Pub 229. The navigator/quartermaster does not have to know spherical geometry, but they must know how to look up the star’s parameters for the time nearest the observation. And several corrections must be made in order to optimize the accuracy of the celestial fix.
@surveyore72 жыл бұрын
Good 'general' explanation. As a surveyor and one who did astronomic observations for nuclear weapon delivery systems, we used this technique primarily to establish direction. We also used it to establish and or verify our location against predetermined markers on the ground (called trigstones). This method whereby you use two or more astronomic observations to locate your position in marine navigation, we also call 'resection'. Other points that have 'known' data sets could be church steeples for instance. I spent 12yrs in Europe doing exactly that, most of which was before 'GPS'. I 'trig traversed many kilometers, bringing directional and coordinate control to where I anticipated a 'firing point would be needed. Mostly this trig traverse occurred in winter where trig stones were covered in over 3ft of snow. Later as technology became more 'developed' they brought a navigation system (gyros and accelerometers) through my points previously established with trig traverse, and found my data to agree with a 1:50,000 Accuracy ratio. Yes we used T2 theodolites and 'math' as well as star finders, and emphemiris.
@Sharkman62758 жыл бұрын
That was most simple explanation for celestial navigation I have ever heard! Thank you!
@Uhlan_10 жыл бұрын
Armed only with a sextant, a book, some math, AND A CLOCK!
@hunterplayshd382010 жыл бұрын
Right, that's what was weird to me. What if you don't know what time it is?
@Rebius10 жыл бұрын
HunterPlaysHD in the old times, when sailors didn't had a watch on board were perfectly fine just by guessing the time and were pretty good at that, didn't had as much nonsence to care about like our modern culture and it was also extremely important and useful as you can see ;)
@wuteverfloatsurkayak9 жыл бұрын
Rebius They also used the stars to tell time.
@2adamast8 жыл бұрын
+leigh tyrrell An astrolabe can tell time with stars. But local time only, no way to know if 3 a.m. is New York local time or a local time 300 miles more east.
@zengerz7 жыл бұрын
astrolabes prove geocentric universe too :)
@michaeldowning15332 жыл бұрын
Hello, I know absolutely nothing about navigation. Isaw this film"Adrift" a true story about a Couple (man and women) who were given the Job of sailing this well equipped yacht across the Pacific. Sadly they ran into a fierce storm, the boat got completely wrecked, the man (an English guy) was thrown overboard and sadly died and the American lady came to to find all navigation equipment completely destroyed except a sextant.She is seen looking through this sextant to try and find her position and it was the vastness of the sea that she was in that made me realise the importance of knowing something about knowing where you are and which direction to want to go. Your simple but clear description of finding our roughly where you are at sea was great. Thank you. I'll have to get that book with the funny title..
@TheJarhead7011 жыл бұрын
Thank you for your service. I was a Marine NCO and later in my career an Army Officer. I did operate a pair of LPC's (leather personnel carriers). I am new to sailing and will use D.R. plots with running fixes to support electronic navigation. Great information. Regards Jarhead 66
@hughheron45329 жыл бұрын
Finally someone xplained this in a way that the average joe can understand.Hats off to you sir.
@poly_hexamethyl3 жыл бұрын
5:00 Isn't this pretty misleading? I mean, the base of that triangle isn't a straight line, but follows the curvature of the earth. And the horizons at the observation point and the point underneath the star aren't parallel. I think it would make more sense to draw the earth as a circle and then you can see that the observed angle of the star above the horizon will be 90 degrees minus the angle at the center of the earth between the two points, which is how you get the distance. Another misleading feature of the diagram in the video is that the star is in reality essentially infinitely far away (compared to distances on earth), so the light from the star hitting the two points on earth is essentially parallel, which is important for the geometry to work.
@thesextantthesunandtheholy42742 жыл бұрын
Earth radius value has been debunked with footage of the horizon beyond 9.41 miles away from a one foot eye height. The sextant works only on a flat surface. The radius for the circles of equal altitude can not be curved as a curved line does not provide a vertex for the 90° angle. This instructions given here, in this video are redundant if spherical trigonometry is to be usef. This dude is a religious, globe believing, fundamentalist moron.
@wattdaflat52862 жыл бұрын
@@thesextantthesunandtheholy4274 Wow, very interesting. How does the sextant work on a flat earth, then?
@wattdaflat52862 жыл бұрын
@flatearthlogic dot net Ok, you have an angle to a star of 45 degrees with a bubble sextant (no need for dip correction), how do you calculate your distance to the GP??
@Rick-tb4so2 жыл бұрын
I have tried to learn celestial navigation for years reading books ...failed..videos...failed and then you came along, Your video is OUTSTANDING and easy to follow and I finally get it.........THANK YOU.....
@tabletclass11 жыл бұрын
Thank you for that wonderful comment. Clearly you know what you are talking about and bring back a lot of "rusty" memories for me when I was a Navy Navigator. The goal of my video was to give students a general sense of the mathematics that go into celestial navigation. Of course I find it amazing that we can use the starts to locate our location on earth so I try to motivate students by using real life examples of math to become more interested in the subject.
@frankmiller954 жыл бұрын
From personal experience, the sight reduction tables are a massive time saver. Unless there's a dog on board, who eats them, they're preferable to Ageton, which l, ah, never learned. .
@alexxchavezee9 жыл бұрын
@1:45 skip to
@baubljos1033 жыл бұрын
I watched your video to educate myself about sextant use and celestial navigation because it relates to the controversy about whether the oceans are curved - or flat. Based on your video, I'm inclined to infer that the LOP (line of position) and the 900 mile leg of your triangle - are flat. In addition, based on your video illustrations I infer that the ocean must be flat in order for the sextant/navigation method to be effective.
@iveneverseensuchbehaviorin53673 жыл бұрын
the stars are in a celestial sphere. i know you dont understand what that means but it means the earth isnt flat
@baubljos1033 жыл бұрын
@@iveneverseensuchbehaviorin5367 Rather doubtful that you could possibly know what another person "understands", because you can't read minds. So the basis of your claim is bogus. As to the flat/curve hypothesis, the sextant presumes that the measured distances are flat. Similarly, engineers presume that earth is flat when they design bridges and other structures, and airlines fly flat over the flat earth.
@iveneverseensuchbehaviorin53673 жыл бұрын
@@baubljos103 you say my claim is bogus but yet dont say why. makes me think you dont understand it. a sextant gives you the angle something is off the horizon, nothing to do with flat or curved.
@baubljos1033 жыл бұрын
@@iveneverseensuchbehaviorin5367 Well technically I wrote the "BASIS of your claim is bogus" and I explained why. It's bogus because it's impossible for you to know what other people "understand". That's not knowable because you cannot read minds. As to the sextant angles - they are all flat , ie horizontal - and perpendicular. Not curved. You know the word "horizon"??? You know what it means? It mean horizontal - flat at zero degrees.
@iveneverseensuchbehaviorin53673 жыл бұрын
@@baubljos103 okay so you dont understand why a celestial sphere debunks the flat earth, youre just upset i called you out on it. so are you saying the horizon rises to eye level? Because the tons of evidence saying the horizon doesnt rise to eye level would debunk your claim about the sextant correct?
@armedmariner2 жыл бұрын
I like idea of part B - an example. I want to see how you look stuff up in the book. I want to know how to derive the “900mi” LOP circle. Having said all that - BRAVO to you for making this easy to understand. I love navigation. Always have. Always will. My dad once took me for a ride in a heavy snowstorm in NH. He pulls off a dirt road and parks. He shows me on a topo map roughly where on that road we were. He then showed me a roughly parallel road a few miles distant from the one we were on. He produced a compass. Oriented it to the map. Showed me how to find a heading. He said “you think you can walk that heading and come out on that other road?” I mean SURE - it was a long way away but if I could come close to following that heading it was gonna be as easy as shooting fish in a barrel. Out I went into the woods all alone with that compass. Heart beating. Sweating too. But I followed that heading. I came out on that road probably 3 hours later. It was getting dark in the sky and I just waited. I heard a car coming. It was dad in the old Chrysler Newport. He pulls up and rolls the window down and says “I think you know how to keep from getting lost now right?” YUP. Every kid should be given that experience. I loved him for that. What a great thing to build confidence. Thanks Dad!!
@twocyclediesel1280 Жыл бұрын
It’s a great experience to navigate through the woods like that. I hiked way back in the Adirondacks once. Simple heading in, I came back out on a 180 degree opposite bearing. I was deer hunting so I was meandering a little as I walked. After all, the road I was parked on ran east / west, and I was heading south. Couldn’t be easier. I got to the road at dusk...where’s my car? I walked east to the first bend in the road, no car. Walked back the other way to the next bend, no car 😆 I was getting very cold and anytime I was walking in one direction, I’m thinking that I could be walking the wrong way! It was a bad feeling. I obviously found it eventually and that heat felt so good. I learned from that. Always add a little intentional error into the bearing so when you get to the road, you definitely know, “OK, I hit the road, now I have to go east (or west) to find my car”. I think the official term is “aiming off” in the “BEMAC” book. “Be expert with a map and compass” I do love working with a topo map and compass, good times.
@armedmariner Жыл бұрын
@@twocyclediesel1280 when sailing, common practice is to “pinch to windward” - you can’t sail directly into the wind but you go as close as you can. You try to navigate so that as you approach your destination harbor or anchorage you only need to steer downwind to get where you are going. Easier than fighting upwind tacking one side then the other. It’s common to say “keep steering high” up into the wind - as high as possible. I absolutely love navigation. There is a book I have that I treasure called We The Navigators. About Polynesian sailors who could sail hundreds of miles between islands with NO navigation instruments. Those guys are a dead breed now. The book was written by a scholar who studied their last generation. He unfolds a ton of stuff that was revealed to him in the course of sailing with those guys. Phenomenal what navigation THINKING can do for you if you keep your senses about you.
@twocyclediesel1280 Жыл бұрын
@@armedmariner That’s very interesting, I’m going to get that book. Thank you! I live on a huge river in the SE near the sound and would love to get into sailing. Unfortunately I’ve seen, and worked on a few too many boats that have sunk. I’ve decided I don’t want the hassle of owning one. It must be a great feeling tho. My grandparents lived on a lake in the already mentioned Adirondacks. They had a “mini fish” sailboat and I had so much fun with that as a kid. A bigger boat, and all the skills involved in sailing and navigating...must be a blast! Thinking about how ppl, like the Polynesians, did what they did is truly amazing.
@tabletclass11 жыл бұрын
Thanks for the great feedback. I agree with your comments. When I made the video I just kind of created it as I was think about it. Nevertheless the topic of navigation and teaching the mathematics around the subject is huge and offers several approaches. Thanks for watching!
@MISHA123147 жыл бұрын
It's easy to measure "altitude" of a celestial body, correct according to height above horizon, upper or lower limb, etc. Subtract from 90 degrees. This is your distance from the body in nautical miles. Best to shoot body's that are due north or south for latitude, and due east or west for longitude. Position of bodies are listed in the "nautical almanac" in longitude and latitude according to date and time. Each "fix" results in a triange on the map, or a distance in nautical miles when subtracted from 90 degrees, to the body. Problems develop because maps are not true d/t curvature of the earth. The map triangle can have three 90 degree angles which is 270 degrees (or more!), so conventional trig is worthless except for figuring the distance to the body with your calculated position on a distance line from the GP (geographical position, aka long. and lat.). Also, you must assume longitude to get latitude, and vice versa. So, at best, especially with a time that is off (one second = 1 nautical mile), problems develop regarding actual position vs. calculated position. Also, arcs drawn on a map are not true circles (grid lines on the map do not make a true square). There are "cheat sheets" that can be used for celestial navigation, which seem more accurate than the actual hand computed fixes. Corrections are often made using a "trafrail log" which measures distance covered (not corrected for current!). In short, oh brave explorer, be sure to have a modern system such as GPS to guarantee accuracy of your navigational skill and provide information when the weather is bad to keep you out of trouble!. There's a reason celestial navigation has taken a back burner. It's fun to play with to see the difficulties, but that's about it. Thanks for the site!
@peterbeefchicken52377 жыл бұрын
Thanks a lot for the details! It may even save someone from big troubles.
@seikibrian86416 жыл бұрын
+ Thomas Dobyns "It's easy to measure "altitude" of a celestial body, correct according to height above horizon, upper or lower limb, etc. Subtract from 90 degrees. This is your distance from the body in nautical miles." To be precise, it's your distance from the point ON EARTH that the body is directly overhead of, not the distance FROM THE CELESTIAL BODY...which would be 207,560 (moon), 80,776,388 (sun), or more nautical miles away.
@seankivler19576 жыл бұрын
... and how, pray tell, will we EVER measure and compute the 'PZS' triangle?
@iveneverseensuchbehaviorin53672 жыл бұрын
flat earthers sure talk big when they dont even have a map yet
@AlexZander688 Жыл бұрын
Read the description for the video: "SPECIAL NOTE: The earth is round/oval, so my use of right triangles is a simple math model to explain the basic concepts of navigating by the stars. However, the actual math needed to perform celestial navigation involves trigonometry on a sphere- which is very advance math- as such you should watch the video knowing that right angle trigonometry is not actually used in navigation because the earth is a sphere."
@tabletclass11 жыл бұрын
Hello and Thank you for your service as well. Before I was a Navy Officer I was in the Marine Corps (enlisted 87 -91) - Semper Fi. As you stated navigation uses several skills and methods. Knowing how to DR is key as it's too difficult to update your position with celestial nav only.
@tabletclass11 жыл бұрын
Hi Ken- thanks for watching the video I'm glad you enjoyed it. I'm a math teacher however I love engineering and other science topics as well....
@rawnukles9 жыл бұрын
The two LOP circles would intersect at two points, two fixes. I guess I third star would tell you which fix was the right one.
@wuteverfloatsurkayak9 жыл бұрын
rawnukles I thought of the same thing. If you are alert and knowedgable enough to calculate this, you could probably estimate where you're at based on velocity and your previous known position and thus you would probably already know which of the two points was accurate; but the third LOP would eliminate the wrong position with certainty.
@Argos100i8 жыл бұрын
+rawnukles The second intersection is probably in some other ocean, so the navigator does have a clue.
@rawnukles8 жыл бұрын
Of course common sense rules out the second intercept.
@user-pf2hv8qw1s6 жыл бұрын
Yes you could rule out the second fix unless the two circles were tangential to each other. In that case they will only intersect at one point.
@garychap83846 жыл бұрын
rawnuckles, in practice the error margin takes care of that, also... as wuteverfloatsurkayak said ... you have other techniques such as the running fix... one LOP+DR gives you an EP (Estimated Position) In actual fact, it's typically less important to know where you ARE than where you're NOT ... so, you'd typically be more concerned with best avoidance than perfect position. In practice, trying to be too accurate is very dangerous. For example, when you take three bearings and transfer these to a chart you typically get a triangle, not a point. It is so tempting to say "I am within this triangle" ... but to be inside of the triangle you'd need all bearings to be off in the same direction ... all bearings, however tight, will be off to one side or the other with near equal probability - so there is actually more chance that you are NOT inside the triangle! Technically, your actual position would map as a blurry donut, with an area of decreased likelihood inside. So, always accept the error margins with dignity! Never try to convince yourself of where you ARE ... but simply seek to be damned sure about where you're absolutely NOT (rocks, wrecks, windfarms, coastlines, busy TSS's, etc) ... and keep checking to make sure you remain 'NOT THERE' during your passage. Having even had my chart-plotters GPS throw me a silly offset now and then, I'm far less concerned about where I truly am these days ; ) I know, that sounds weird, but it's a fact we sailors all have to accept sooner or later : )
@TacMind2 жыл бұрын
Flat Earth brought me here. Thank you for your video
@flat4life6 ай бұрын
This would be impossible to do on a globe. Sextants prove flat earth.
@marcg16862 ай бұрын
@@flat4life Why would this be impossible on a globe?
@flat4life2 ай бұрын
@@marcg1686 How do you get a 90° triangle on a curved surface? Not to mention, this 90° triangle spins around in a circle… It only works on a flat surface, it can’t work on a globe.
@marcg16862 ай бұрын
@@flat4life We don't use 90° triangles when conducting celestial navigation.
@flat4life2 ай бұрын
@@marcg1686 Yes you do, you use 90° right triangles it’s right there in the very video that we just watched. He actually shows a graphic.
@bababoombaboom24656 жыл бұрын
I think for what you're trying to show here it would have made more sense to take the simplest case so the principles are apparent, and then show how the more difficult cases relate to the simple main idea. As the earth rotates, there is one line of longitude that is closest to the sun, halfway between the dark edges where night begins. This is local noon and in theory it is a razor-sharp line, zipping along about 1000mph near the equator. Everything on the 'morning' side of it is seeing the sun rising, everything on the 'afternoon' side of it sees the sun going down. Since the earth is turning at a steady rate, if you know the clock-time difference between your noon locally, and a reference longitude - Greenwich, by convention - then you know your longitude. Measuring the highest point of the sun's arc in your sky gives you your local noon. The other even more simple case is your latitude, from Polaris. Since Polaris is above the north pole, it is straight overhead at the pole (90 degrees) - and just on the horizon at the equator (0 degrees). All the time. And everything in between follows perfectly. At 37N latitude, Polaris is at a 37 degree angle. Once you understand these basic ideas, their more complicated manifestations relate back to something pretty intuitive. The sun moves up and down in the sky according to season, so you need to add or subtract declination if you use it for latitude. Sounds a bit weird, but when you see that you're just trying to measure an angle, the fact that the angle shifts because the earth tilts relative to the sun, isn't so hard to come to terms with. Starting right in with random stars and charts and almanacs and trig is too much for a beginner. In my humble opinion.
@petersushkin5 жыл бұрын
Hi! Listen, I am from Ukraine, and my native language is Russian. I just wanted to thank you and tell that I couldn’t find more simple and obvious explanation for this topic on my native language! You are awesome, thanks again mate! :)
@richardcranium84084 жыл бұрын
5:05 “I’m not going to get into the math because that’s not the purpose of the video.”. Huh? Why title your video like that then?
@Somethingisntright642 жыл бұрын
The radius of your “Circle of Equal Altitude” for star A would be 2400 NM, not 900 NM. ZD = 90* - Ho x 60NM/*
@davesantiago18272 жыл бұрын
Yes and what does this prove? It proves the earth is FLAT. Cant have 90 degrees on a sphere thats dropping away from you at 8 inches per mile squared. Im not trying to be condescending. Im just trying to make people see the truth.
@Somethingisntright642 жыл бұрын
@@davesantiago1827 90 degrees to the subpoint of the body. Your position is somewhere other than the subpoint which allows you to derive the zenith distance.
@davesantiago18272 жыл бұрын
@@Somethingisntright64 sorry for the aggression. I thought you were in another thread I was arguing with someone
@davesantiago18272 жыл бұрын
@@Somethingisntright64 yes so you have your zenith pulled from a celestial object then to horizon to you. 90 degrees every which way on a circle of equal elevation. Proves the earth is a flat plane. Its a fact that cannot be denied.
@TheIsmaelIsaac2 жыл бұрын
Just checking to see where the 60 nm to get 900 or 2400 miles came from??
@deaconallan2 жыл бұрын
As a former ships captain (merchant), and a navigator for many years, before the advent of GPS, although we did have DECCA and in the western hemisphere LORAN, these did not reach out to sea, and were only useful near land. Thus, celestial navigation at sea. Basically, three items are needed: a quality sextant, a good accurate timepiece (Chronometer), and sight tables, I prefer to use the Air Almanac because it was much simpler than HO229 and sights can be worked out much faster. A stopwatch is also helpful. Although I have been retired for 14 years, my sextant and stopwatch reside on a shelf in my study.
@marcg1686 Жыл бұрын
Did you ever try to determine Hc using a calculator? I also started with HO249 but I only use a calculator now. Way easier.
@tabletclass11 жыл бұрын
Hi Bruce. Thanks for watching the video. Yes indeed I think you should study the process more and it's really a joy to be able to navigate by the stars. I wish you all the best and thanks once more for watching my video... John
@Frups123456782 жыл бұрын
Congratulations TabletClass Math, you have now become a flat earth poster boy! I understand that it was never your intention and you tried to prevent it by writing: "SPECIAL NOTE: The earth is round/oval, so my use of right triangles is a simple math model to explain the basic concepts of navigating by the stars. However, the actual math needed to perform celestial navigation involves trigonometry on a sphere- which is very advance math- as such you should watch the video knowing that right angle trigonometry is not actually used in navigation because the earth is a sphere.". This however is of no relevance in the flat earth cult, so congratulations to your new found fame!
@johnx93188 жыл бұрын
minute and a half in - still waiting for some information. any more waffle?
@mikenaugz886 жыл бұрын
John X welcome to KZfaq, just click 5 or 10 min in and rewind till it starts to make sence.... like i do lol
@reginaldwigglebottom47316 жыл бұрын
No shit! I left during the 3rd minute of disclaimers. Fuck it, I’d rather be lost
@JamieSmith-fz2mz2 жыл бұрын
A very simple conceptual explanation. As a sailor, I love it. I also like that it works if I don't have a phone or a GPS or any other technology. Except I need a sextant, and a timepiece, and knowledge of stars, and a book (H0229), and a pen. The lesson I'm taking from this is to keep my Garmin charged and drop it in the water. Just giving you grief. Your explanation is great.
@jochenludewig88577 жыл бұрын
Very well done!! Being a total novice with this skill I have been looking for some decent & basic information re positioning/sextant use for a while.....I found your KZfaq clip and now understand the principles involved. You ARE a legend. Thank you from a layman in Australia
@dbeierl7 жыл бұрын
Unfortunately he neglected the basic principle that a difference in observed angle to something as far away as a star can only arise by your own self being aligned in a different direction because you're standing on a sphere. The actual divergence of angle of light rays falling from a star onto any point on earth is far too small to measure with a handheld instrument.
@alfaproximacentauri53359 жыл бұрын
I think this is completly wrong.... how can you calculate this '900' miles having ONLY three angles? Please note the distance to any star is -comparing to the size of the Earth- practically infinite. So I think the author of this video is showing wrong triangle.
@alfaproximacentauri53359 жыл бұрын
***** I am not saying the celestial navigation method is wrong. I am saying the explanation provided by post author is wrong. Look at the triangle he shows: first of all if you have only angles, then you can not say anything about lengths of triangle sides. In addition, assuming the distance of 900 NM is correct: the angle is 50deg, tan(50 deg ) = 1.2, so the distance to the star would be 900 NM * 1.2 = 1080 NM. Not so far, really.....
@19Koty966 жыл бұрын
eh, nautical mile is not a unit of distance, it's a unit of angle ;)
@duane8166 жыл бұрын
wouldn't a nautical mile be a measurement of distance (6076 feet) and latitude and longitude be a measurement of angle (degrees)?
@19Koty966 жыл бұрын
nautical mile is angular distance ))) go figure nautical mile is a section of arc (on a "spherical" surface) defined by its angle
@denisrogers45433 жыл бұрын
nautical miles are units of distance. one degree at the center of the earth represents a distance of 60 nautical miles on the surface of the earth. There are 5,400 nautical miles between the equator and either pole.
@solahudinudin9068 жыл бұрын
hi you use flat earth model. Interesting.
@carl203crazy28 жыл бұрын
Sorry, he is using a bad example that means nothing. And celestial math is sphere based.. NOT flat.
@dejanhaskovic52047 жыл бұрын
WHAT AN IDIOT YOU ARE!
@carl203crazy27 жыл бұрын
Really? I think teaching celestial math for over twenty years contradicts your immature response.
@garychap83846 жыл бұрын
Solahudin ... yes, I laughed at that too : ) There's _"simplifying"_ ... and then there's _"playing into the hands of the flat-earth idiots"_ and, however well intentioned, this is definitely achieving the latter ; )
@19Koty966 жыл бұрын
The funniest part about trigonometry is, that it works regardless of what you take as base.
@tabletclass10 жыл бұрын
Hi Brian- I agree with your comments; finding your position using a sextant really is an amazing feeling as it connects you with so much history of how people navigated in the past
@flattenthecurve86232 жыл бұрын
It only works on a Flat Earth.
@tabletclass11 жыл бұрын
hello demmy- maybe sometime in the future I can put together a video on various coordinate systems. Thanks for the suggestion and feedback- keep learning!
@jackiechan36912 жыл бұрын
Erm ....please explain why You fix Ya spot by using a refracted horizon (so no straight line for an angle) then Ya use 3 stars n with triangulation... giving You a massive massive area of Ya position of equal altitude.. but then comment we live on a sphere? After jus using a tool to debunk the sphere!! What Ya been smoking? You can not get a right angle on a globe n no plumb lines hang down vertical perpendicular to horizontal wherever Ya are on earth .. forget pre supposing balls n molten iron cores, Ya jus destroyed Your entire presentation lol
@certified_boogeyman Жыл бұрын
Proof the earth is flat
@iveneverseensuchbehaviorin5367 Жыл бұрын
not one flerf knows how celestial navigation works. proof flat earth is a scam
@iveneverseensuchbehaviorin5367 Жыл бұрын
proof flerfs cant defend their claims
@DivergentDroid Жыл бұрын
@@iveneverseensuchbehaviorin5367 A sextant is an angle measuring device. Angles are defined as two straight lines meeting at a vertex. It is impossible in math to take an angle from the surface of a sphere as any Cad program will tell you. The celestial navigation books and this video shows you taking an angle from the flat horizontal plane. The books call this the equatorial plane. They also state cel nav uses the horizontal coordinate system. They tell you at sea level you do Not need to correct for height of eye or dip as some call it. The sea level itself is considered the flat horizontal plane cel nav uses to take the angle from as shown in this video. Nothing you do in the tables after that angle is taken will negate the fact you used a flat horizontal plane to obtain the angle. Earth measured Flat by way of elevation angles. No way you can get out of this.
@iveneverseensuchbehaviorin5367 Жыл бұрын
@@DivergentDroid the line from the sextant to the horizon is a straight line, destroyed your huge paragraph in an instant
@DivergentDroid Жыл бұрын
@@iveneverseensuchbehaviorin5367 Are you Daft? It didn't destroy my position, it agreed with it. Don't you understand you cannot have ANY straight lines on a sphere? If that's the best you can do to rebut my paragraph then I say Welcome to Flat Earth!
@sakichatzichristidis89328 жыл бұрын
need to be more to the point too long intro
@larryhansen2474 жыл бұрын
if indeed you saw a star at 50 degrees above the horizon you would be 2400 nm from its ground point, not 900 miles
@tabletclass11 жыл бұрын
On your question about the use of a sextant at night. It's easy to use a sextant however it takes alot of skill to take accurate "shots" of the stars/moon at night especially when your ship is rolling and pitching ; I was never that good as it takes YEARS to develop the skills of master navigators.
@FTFEOfficial2 жыл бұрын
Uh...that's all wrong...there are NO triangles in celestial navigation...
@paulwielgosz60469 ай бұрын
Unless you are directly under the celestial reference the triangle is a result of the elevation
@stellerpolaris9 ай бұрын
@paulwielgosz6046 idk why people fight so hard about the gp of the elevation angle making a right angle triangle from the gp at the horizon to your location in the boat.
@stellerpolaris9 ай бұрын
Ohh what are you talking about?
@iveneverseensuchbehaviorin53679 ай бұрын
@@stellerpolaris There is no triangles in celestial navigation, how hard is that to understand?
@dqf98307 ай бұрын
There are spherical triangles
@tabletclass11 жыл бұрын
Hello, QM rate is excellent! You will be on the bridge (pilot house) of the ship and see all the action; also you wont feel trapped inside the ship. As to the math I would get really good at working with decimals. Also you could learn how about angle measurement in terms of degrees-minutes-seconds. However the post important thing is to learn from those senior QM; listen to what they say. It will take a few deployments but you will master all the critical skills of nav at sea-good luck!
@tabletclass11 жыл бұрын
Celestial navigation was developed over 1000s of years. At first navigators used more basic methods before developing the sextant, book or clock. However these methods could not produce a fix so navigators never knew their exact position. It was not until the 1600s where accurate clocks where made to handle the rough movements for ships at sea that navigators could determine longitude - then the art of celestial navigation became more like what the video described.
@hillside64012 жыл бұрын
Proving earth is flat earth. Very nice 👍🏻
@mactallica92932 жыл бұрын
You clearly don't understand navigation. Or trigonometry
@hillside64012 жыл бұрын
@@mactallica9293 o nice why don’t you explain why I don’t. Oh yeah I actually do and you don’t. That’s why you don’t elaborate sphere boy. Gtfoh
@iveneverseensuchbehaviorin53672 жыл бұрын
@@hillside6401 flat earthers dont know how to celestial navigate, you cant find one who can do it
@hillside64012 жыл бұрын
@@iveneverseensuchbehaviorin5367 I have several times with my grandpa. Have you? We even used our sextants upside down. Great proof of flat earth. You don’t have to like it. 😁
@iveneverseensuchbehaviorin53672 жыл бұрын
@@hillside6401 you can say anything you want, you wont demonstrate how to use a sextant to find your location because no flerf ever has. They couldnt explain how to do it because that requires saying the earth is a sphere. so all you flerfs do is lie lie lie.
@carl203crazy28 жыл бұрын
John.. Please delete this video. You are embarrassing the rest of us who know how this is done. Your use of 'thing' and the totally wrong distance in your example is just poor. If you are going to reference an example, use the proper terms and correct information. 50 deg observed altitude equates to 2400 nm from the stars geographic position. Which is tabulated in a book by-the-way. And, You do not need a major in mathematical study to determine this fact. It's simple multiplication. Oh.. I think it's HO pub 229? really? maybe it's something else. Maybe a Nautical Almanac? Maybe Sight Reduction Table? Sorry, I couldn't watch past the 900 mile thing... 17yrs ocean navigation, U.S. Navy Instructor (Celestial Navigation) Good luck
@postholedigger87265 жыл бұрын
Where does your radial distance from the GP come from? You take a sextant reading of 50 degrees and you know that you are 900 miles from the geographical position. How do you know this? david
@kr97358 жыл бұрын
Sod sitting in this fella's class all day.....zzz
@kamisview4 жыл бұрын
Best explanation I've heard wasn't even looking for this but I just got hooked.
@southerntexashomestead50284 жыл бұрын
Awesome class. If current teachers would use this method of teaching more students would grasp the skills of mathematics and value it's usefulness. Great job!
@RobinMsPkBlog11 жыл бұрын
hi there, nice introduction to celestial navigation but i think it could be improved by using a model of a round earth where all rays coming from a star are parallel due to the infinite distance he's away. Then you could simply show that you get different angles on different positions due to the bend of the earth's surface and as a little supplémentaire you then could show that the difference in degrees you obtain can directly be converted in nautical miles and everybody would be satisfied ;)
@tabletclass11 жыл бұрын
Oh wow MoBoards- maybe I will do a video. MoBoards are a great way to show how vectors in math are used in navigation. I know what you mean being fast- if you do MoBoards as part of your job you end up being good. I actually used to work my MoBoard problems right on the radar screen using a marker pencil- could do all CPA problems that way; only used actual MoBoard for formations, Screen Kilo, Form 1, etc. Thanks for watching!
@tabletclass11 жыл бұрын
navigating by the stars has evolved over 1000s of years; some of the ancient methods used basic tools just to hold study the latitude of the north start; this keep navigators on a one Lat. until they reached the coast; at which time they switched to piloting along the coast; the use of a sextant was introduced much later on as science and math evolved as well..
@tabletclass11 жыл бұрын
Thanks for your comments. During the day you can use the sun to get LAN (local apparent noon) which gives you a LOP (line of position). Celestial navigation is part of the overall navigation effort on board ships. Navigators also need to DR (dead reckon) which is updating your position by using your course, speed and last fix. Of course the more you estimate a your position using DR the less accurate your position; hence using the sun during the day can help update your fix;
@HOOOLD_ON2 жыл бұрын
Hi TableClass Math. Are you aware this video has been copied, cut in half and used as proof of celestial navigation on a flat earth by a KZfaq channel named "Flatzoid FE" ? Question: Did you allow him to use your material, or did he just steal it? If he didnt ask for permission, I see it as a clear breach of copyright rules. Here's the link to his video kzfaq.info/get/bejne/fJucnbebzbfMiqs.html
@phileasfogg31074 жыл бұрын
If you measure a star at a height of 50 °, it means that you are on a circle whose center is vertical to the star and whose radius is exactly 2400 nautical miles, not 900 .... Because Zenith distance = 90°-50° = 40° and 40° = 2400' (=2400 NM)
@CuckOmelette2 жыл бұрын
900 was a random number. He said that.....
@Ratlins95 жыл бұрын
Superb video, the ability to break down a sophisticated method of navigation for laymen to understand shows high intelligence. Thank you!
@chrismoller887210 жыл бұрын
Hi A nice explanation. One comment. You describe that with two stars you get a fix. Technically, this is not true. Two stars will give two possible location points because the circles of equal altitude intersect at two points not one. It takes three stars to uniquely determine a position. In practise, you have been keeping track of approximately where you are (dead reckoned position) so for practical purposes you can pick out the correct point with two stars.
@branni65384 жыл бұрын
These arcs of reference is how the Astrolabes and chronometers came about. The polynesians were very accurate and they used memory, songs, stories and 3d stick charts to remember star nav. In fact all the accounts I've read of early western mariners meeting the south seas people were blown away by their level and ability of natural navigation, their culture and deep connection with the stars far surpassing our mariners and their scientific gadgets and gizmos and charts and books. Sadly most of that knowledge is gone.................... A simple quick arc reference for latitude would be 90* minus 50* gives you 40*. 40* can then be used to calculate distance etc away from point A and the celestial sphere rotation plus the location of star A will give you an accurate reference for direction. This can be done super quick with outstretched hands and is very accurate. My location here in the UK is 55.5* which is 5 and a half hands up from the horizon or down from the pole star. It's accurate too if you know the suns arc for the four seasons too. But it's better to learn it as the Polynesian and the desert Bedouins did by memory. Never rely on kit.....................
@justinwilliam56938 ай бұрын
do you have any resources you recommend?
@9642710 ай бұрын
If the earth is flat, explain hemispheres. Why can't New Zealand see the big dipper? Why is it summer in the northern hem but winter in the southern?
@MoosesValley4 жыл бұрын
I used to be able to do Celestial Navigation with a Sextant, a clock, and a current Nautical Almanac - the book of tables for the positions of the closest stars, our solar system's other planets, and our sun during the day. The math wasn't hard. The more difficult math was in the construction of the tables for each celestial object for the coming year. I'm pretty rusty now, but it wasn't hard. Using a Sextant requires some practice to get good readings, and is especially difficult on rough seas, in windy conditions, and/or in small boats. Get regular practice, take readings for 3 stars, and you will soon get your position amazingly accurately.
@shahzalak6504 жыл бұрын
best explanation so far for this topic found on this platform
@khairilimam2654 жыл бұрын
How did you define the 900 mi distance?
@fyoung4610 жыл бұрын
Very nice illustration! I see your example is on the TIGHAR article abouit searching for Amelia Earhart In one of their articles they have suggested that FN was confused and was reading the wrong dated charts and instead of using Jul 3 data he may have been using Jul 2 data or vice versa. In fact one person goes into a very long dissertation, which is almost convincing, until you realize he fails to mention one very important detail, which would have been quite obvious with the use of the naked eye alone. (the MOON was available that night) The argument has also been supposedly confirmed by some navigator and that these chart errors could have put them 59.14 nm farther east or west of where they actually were. That may be OK for star error, however the MOON behaves quite differently as it cycles is every 28 days. The stars only vary a few minutes from day to day.. As example lets just say near the IDL where they would have been the coordinates are Latitude S0* 06.1’ Longitude E 179* 56.1’ If FN had been reading the wrong day's charts the MOON would have shown them to be over a thousand miles off course The Moon From July 2 and July 3rd 1937 shows a difference in Hc as 14* 40’ and Dec 14* 14’. This difference is at total of 28 degrees 54 minutes and error of 1734 nm.
@dataderivations27373 жыл бұрын
I'm studying the "Sextant Crop CIrcle" and this information exchange was most helpful for the linguistic studies being performed.
@tabletclass11 жыл бұрын
I know what you mean- MoBoard problems were great especially when doing things like winds for a helo. A radar screen can be used as a MoBoard so you can plot contacts on your screen and get a CPA; then determine what course correction is needed to open up a safe distance; this stuff is really important for large vessels as you need lots of time and distance to manuver
@tabletclass11 жыл бұрын
hello- I have not anymore videos however I may look into creating more- I love navigation and find it very interesting to see how math is used to find your location
@arturocubria93983 жыл бұрын
First time I watch a video about navigation that I actually understand. Thanks
@tabletclass11 жыл бұрын
Hi Eric, Yes indeed you are correct; thanks for watching the video and it's great getting feedback from people the understand the skill involved to celestial navigate
@flattenthecurve86232 жыл бұрын
Excellent Flat Earth Proof. As a surveyor, I can also verify that every survey of every piece of property on earth is measured using horizontal distances.
@tabletclass11 жыл бұрын
I'm the same way- more data the better. Thanks for the great input on the videos, I think I might brush up on MoBoards and do a intro video; all the best! John
@seanpatrick7811 жыл бұрын
Nice work! I've been studying cel. nav. for a couple of years now and as you say, it's a great way to learn about trigonometry, history and other subjects. Everything in the video is essentially correct. I heard you say you weren't sure about a couple of things, so here's some very minor corrections: The book you were referring to is actually the Nautical Almanac. The circles of possible positions are called "circles of equal altitude", but when plotting them on a chart, only a small...(cont.)
@EDFETHER11 жыл бұрын
You reference Ho229 as the book containing the celestial data. That is incorrect. The book you are attempting to reference is the Nautical Almanac. Ho229 is the book (actually a series of books) for the Sight Reduction tables, so you can do the math without a calculator.
@ushoys6 жыл бұрын
In addition to a sextant, the book and some math you also need CHARTS and an accurate CLOCK to plot where you are.
@flattenthecurve86232 жыл бұрын
Yes, and it only works on a Flat Earth.
@TheJarhead7011 жыл бұрын
Take care. I'm an old Jarhead that went through ITR with an M1 and used an M14 before the Matty Matel special was forced on us. Best regards and thanks Jarhead
@tabletclass11 жыл бұрын
indeed; 2 LOPs are not enough; 3 LOPs are the min to have a basic idea of your location; also to your point navigators need to know how to DR using estimated speed and direction- all skills navigators need to really find an accurate fix
@CaptDenis7 жыл бұрын
Very good basic explanation. However, you would use a nautical almanac to find the present position of the celestial body for the date and time, new is issued each year. Then go to the HO 229 to get for lat and long variation or declination. Also, the Bowditch tables will quickly simplify the math for finding the angles. The mariner needs to understand that this is a very simplified explanation due to the exactness of time and high of eye, etc.
@strannick22125 жыл бұрын
At 3.32 in the video, he mentions a book,-- Ho 229,-- that navigators use to find the ground position of a star. Actually the book used to find the ground position of a star is not Ho 229 but either The Nautical Almanac or the Air Almanac. Ho 229 (sight reduction tables that precompute the complicated math) are other tables that are used to find the altitude of that same star from an assumed position. The star's attitude from this assumed position is then compared with the altitude as found on the sextant. The adoption of an assumed position is a contrivance used in order to be able to plot a position line on a chart. Otherwise the intercepting arcs (lines of position) cover such vast areas that they are not amenable to be plotted other than on a globe. For instance for a sextant altitude of 50 degrees the line of position (arc of the circle) would have a radius of 2400 nautical miles.
@billycox7925 жыл бұрын
Shoot, not going to go into the math, eh? The math is why I'm here.
@foster37again11 жыл бұрын
Where, on the surface of the Earth, do I place that first 900 mile circle?
@steinrich562 жыл бұрын
Brilliant little vid..! You explained it so well. Greetings, and many thanks, from Australia.
@some-other-time7 ай бұрын
This is so concise -- a perfect refresher!
@tabletclass11 жыл бұрын
to actually plot a fix on a map/chart it rather involved; my goal was to give a general understanding of the process but in actual practice it takes training to develop ad transfer fix data onto a chart
@jorgepinal36218 жыл бұрын
Great starting point, thanks ! So to cap it off celestial map to know one or two stars sextant the HO-229 Accurate time (know what time zone) What would it happen if I want to take the measurement during the day? Again Thanks,
@EDFETHER11 жыл бұрын
I really enjoyed your video. I liked the way you drew it out on an actual picture of a horizon. I recently went on a cruise, and I took my sextant with me. I shot star fixes that were within .75 of a nm of the GPS fix. I commented this to the Captain of the ship, and he called it a fluke; that Sextants were inaccurate; and that he hasn't touched one in 20 years. I think he just stinks at Celestial Navigation and discounts it out of hand. Its sad he's grown lazy because of GPS.
@antoniothales47219 жыл бұрын
Congratulations!!! Your video is a lot easy to understand and well explained. Please keep with the classes, I am learning a lot. Thank you
@rolanddutton70597 жыл бұрын
The reference to the circle drawn as an LOP isn't correct. It's a "circle of equal altitude". Using Pub. No. 229 or Pub. No. 249 (which has the more common and useful navigational stars) alone will not provide you with anything useful unless you have an Ap. Latitude and LHA. based, of course, on GMT/UT1 time. And without The Nautical Almanac you can't know much of anything position wise except a rough approximation of Latitude (so long as you know the sun's declination for the day and time of the sight). You only can obtain an LOP once the sight reduction is accomplished and Hc is compared to Ho and plotted on a UPS. The video, while nice, overly simplifies celestial navigation.
@garycherwonick8429 Жыл бұрын
Some important steps missing: Then calc the Zenith Distance based on Sextant Altitude (Hs), 90-Hs: 90-50= 40 deg. For the Northern Hemisphere, in your example, the Zenith Distance is 40 degrees, which converts to 2,400 NM (40 deg x 60). [1 degree of arc on a Great Circle is 60 NM]. This means that if you suddenly went 2,400 NM toward the Star you’d be at the ZENITH (Star directly above or Hs = 90 deg). From the Almanac at the Fix Time: 1) Obtain the Star’s DECLINATION - equivalent to LATITUDE AND obtain the Star’s Greenwich Hour Angle (GHA) from the Almanac - equivalent to LONGITUDE measured Westward from the Greenwich Meridian (Zero Deg Long) from 0- 360 (No East or West). To plot the curved LOP you’d have to draw an arc 2,400 NM Radius from Star’s ZENITH position (Declination and GHA). As you discuss another separate observation with another Star can determine your FIX with a second (and third) curved position line. Although tricky, due to Convergence (of Longitude), and depending upon the type of projection of the plotting chart you could take a True Bearing TO the Star at Fix time, then back-plot a Great Circle line FROM the star, compensating for longitudinal difference from the Star and your approximate Longitude? That way you’d have a Curved LOP and an Azimuthal (straight) LOP for a 2-position line FIX My background: I was an Air Navigator in the Canadian Forces on C-130 Hercules. We did 3-Star Fixes with a Periscopic Sextant using the INTERCEPT METHOD of plotting whilst travelling at 330 Knots to HOPEFULLY obtain a small “Cocked Hat” from 3 LOPs! My $0.02 worth.
@marcg1686 Жыл бұрын
Did you use Ho249?
@garycherwonick8429 Жыл бұрын
@@marcg1686 I’m familiar with AP 3270, Sight Reduction Tables for Air Navigation (3 Volume set) - essentially simplifies Spherical Trig into a tabular format without having to apply Cosine Law for Sides and Angles. I reckon HO 249 accomplishes the same task? The SIMPLEST observation is at Local Noon or Meridian Passage to avoid NOT using Sight Reduction Tables - for sailors the “Noon” sextant reading gave them THREE important pieces of Navigation. 1) LATITUDE: At local noon or Meridian Passage the Sun is at its highest point of its apparent motion of and path from East- South- West. At its highest point determined by sextant readings to obtain the GMT of the Sun’s highest angle above the horizon, at that moment the Sun and observer are at the same Longitude and the Sun due South (180 deg True). This means that the geometry is a straight line - i.e. no triangles. In the Northern Hemisphere LATITUDE = 90 deg minus the Sextant Altitude (Hs). 2) LONGITUDE: By noting the GMT of Mer Pass and comparing it when Mer Pass occurred at Greenwich, UK, the time difference can be converted to an angle or Longitude, based on 1 hr (60 min) EQUALS 15 Degrees of Longitude or 4 minutes time = 1 degree Long. Note: It is essential to determine the GMT of Mer Pass at Greenwich, which for any given day will var by up to 30 minutes. This is due to the Equation of Time, which compensates/ corrects for Earth’s OBLIQUITY (due to the 23.5 deg tilt of the axis from the vertical as it orbits the Sun, AND ECCENTRICITY, which is the variation in orbital speed as the orbit is an Ellipse, not a Circle. Two ways to obtain Equation of Time: 1) consult the chart or table to obtain the day’s correction - e.g “Sun Fast (or Slow) from Zone Time”; 2) in the lower right corner of the Nautical Almanac the MER PASS time is shown for noon (e.g. 1214 means that when the Sun was at its highest point the GMT was 14 minutes ahead of the Sun’s Local Noon. By comparing the GMT of Mer Pass at Greenwich and the GMT of Mer Pass at the Observer’s location (“apples to apples”) convert the time difference to Longitude. In the 18th Century the invention of extremely accurate CHRONOGRAPHS enabled sailors to determine their Longitude with time pieces that were diligently adjusted and monitored at the Greenwich Observatory as ships could be away for up to TWO YEARS. A faulty or damaged Chronograph was a serious problem and it was kept in the Captain’s Cabin flat in a gyro-type box that kept it level despite pitch and rolling. Ironically, GPS also uses TIME to determine position! 3) Compass correction/ variation determination: As stated above, at MER PASS the Sun is due South (180 deg True). Simply note the Sun’s MAGNETIC heading/ bearing. The difference is the local MAGNETIC VARIATION. e.g. if the Sun’s heading is 195 MAG the local variation is 15 Deg WEST, so if your planned track on your chart is 240 Deg TRUE, you have to steer 255 Deg MAG. Slightly more than $0.02 worth. Cheers!
@marcg1686 Жыл бұрын
@@garycherwonick8429 They are one and the same. I prefer to do the direct calculation.
@marcg1686 Жыл бұрын
@@garycherwonick8429 I do have to ask you something. Did you ever correct for dome refraction? HO249 does have a table for that.
@garycherwonick8429 Жыл бұрын
@@marcg1686 Dome correction would be applicable to hand-held sextants used in earlier aviation to correct for refraction. When I was a Navigator in the RCAF we used a Periscopic Sextant that “peeked out” just above the fuselage. The Air Almanac published by the US Naval Observatory contains corrections for Atmospheric Refraction, which is greater for low altitude observations - the celestial object appears higher than actual resulting in reducing the Height Observed (Ho). As the sextants were calibrated in Avionics Labs annually each sextant had a mechanical correction to determine Height Corrected (Hc) based on the Ho. e.g. 0- 30 deg,subt 2 mins; >30 - 45 deg, subt 1 min; > 45 deg, 0 corr. The periscopic sextant has a mechanical AVERAGER (ticks like a clock) that takes an average over 2 mins (120 secs) to minimize the subtle roll/ pitch of the aircraft with a thumb-wheel for the Nav to keep the celestial body in the centre of the circular bubble (corresponds to the “horizon”) in the viewfinder as any roll or pitch will make the body depart from the center, so the quicker the body is returned to the center the more accurate the position line/ fix. Therefore the Nav starts his/her shot exactly 60 secs prior to the pre-computed time to 60 secs beyond. The averaged Height Sextant (Hs) in Deg and Mins is displayed in a window. As there is some technique and skill required some Navs would apply a “Personal Correction” based on numerous comparisons of their position lines against an independent, and accurate fixing aid. On the Internet you can search for the USN’s Air Almanac in PDF - free for 1-2 years back to see the info on Periscopic sextants regrading Refraction and more. Cheers!
@nickmerix29004 жыл бұрын
According to your example. The height of the star is about 1073 miles? If you can use trigonometry to find your distance from the 90 degree point you can also use it to find the distance to the star.
@saishyamnilgiri110 жыл бұрын
Thank you! I enjoyed this video. You taught me some thing very important on Astro Navigation. I has got me closer to my goal. Thanks once again and God bless you.
@templetopics10 ай бұрын
GP of stars gives latitude but you have to consider GMT and time zones to figure longitude. Great starter video.
@johnsherwin1104 Жыл бұрын
FYI I have determined from history that 360° 60' 60" DMS latitude and longitude was a prehistorical invention. It ivented hexidecimals for a pragmatic, angular ratio grid on the the stars that also made a standard radian Nautical Miles each minute of latitude (of 1000 standard fathoms or 6000 original feet) at sea level. Fathoms being the familly set of measurements including 2 yards, 4 cubits, 6 feet, and inches used since sailors started using boats instead of everyone walking. That star grid also creates an angular grid on the earth. As a Radian distance, spherical Nautical Mile calculation in a quadrant are greatly simplified by reducing converging longitude distance to true distance multiplied with the ratio cosine of latitude midpoint. The resulting true longitude "distance^ can be used with the direct true latitude distance simply as a flat right angle triangle to have an adequate course forecast. The original ancient foot, in the ancient sailors fathom familly set of 1fathom/2 yards/4 cubits/6 feet/inches, are longer than the yard/foot introduced by English King Edward 1st after 1275 CE used with a 5280 foot Statute mile in a failed attempt to create a 24,000 Mile Equator for a 24 hour day. Typing 1 fathom into ConverPad app shows that the ancient standard fathom was the basis for over Twenty ancient measurements including cubits (Ancient Sumariansand Egyptians), 10 Stadia (Ancient Greeks) per Nautical Mile etc. An English scientist commented after the Edward foot was introduced that there was 6068 of them in a Natical Mile. (About 1.15% different in length.). This DMS ratio is inherently future proofed by providing a 6000 foot Nautical Mile giving an arc second (") of100 feet, a "ten"th if a second of "ten" feet and a hundredth of a second of one foot. Pragmatically, either (foot) distance still works for navigation distance calculations and provides simplistic mathematical navigation - between angular latitude and longitude positions determined without distance - on a line between the centre of the Earth and a DMS grid on the stars. GPS, Immortalising latitude and longitude used on all maps and charts, is accurate to 6 metres or 20 feet (0° 00' 00".20 DMS) or DDD 0.000056° (HiPER Calc app) Few people understand that before the ancient Sumarians and Egyptians (used cubits) latitude and longitude positions provided a control base for bearing triangle (to scale) for mapping and charting without distance measurement of coasts and interiors by navigators and explorers. (Triangulation) This mapping method gained the name Plane Table mapping in the 1400's and was the method of accurate world mapping until about World War 2. Complex 3D spherical math for navigation is greatly simplified when you understand the pragmatism of forecasting navigation from one latitude a longitude point to another is altered along the course by crosswinds, currents, storms and steering ability changing where you end up in distance and/or time. No long course, especially on land or in the air is an undeviating curved line. Since Nautical Miles are radian distance no earth radius calculations are needed. Simply put -distance between latitudes is true Nautical Miles on one side of a right angle triangle - and distance between longitudes on the other side changes by the factor of the cosine of the latitude at the midpoint of the line midpoint in a quadrant. The cosine of zero degrees at the equator is 0ne (1), the cosine at the poles of 90° is zero (0) and between these values will multiply the length between longitudes to provide an adequate true length for the other side of the right angle spherical triangle. Since the curvature of the earth can be considered a constant ratio, flattening the spherical triangle to a plane 90° triangle is adequate to calculate a forecast plane hypotenuse course distance. Lines crossing the equator or longer than 90° outside a quadrant can need calculation as more than one line. Sometimes latitude and longitude might be measured as accurately as one Nautical Mile., but you will never know when.
@YouTw1tFace2 жыл бұрын
If you’re using right triangles, your baseline is a horizontal flat plane. Let that sink in.
@Shandolum22 жыл бұрын
He isn't using a triangle. He is drawing a triangle in his oversimplified explanation, but it is not used for anything. Let that sink in. Try finding a singular flat earther who can accomplish celestial navigation. You will find none. Let that sink in.
@YouTw1tFace2 жыл бұрын
@@Shandolum2 “he isn’t using a triangle” .. “He is drawing a triangle”.. Hahaahahahahah
@Shandolum22 жыл бұрын
@@YouTw1tFace which he doesn't use. It's an oversimplification. You have a star straight up at the GP. You have an angle to the star at the observer. You calculate a distance between the observer and the GP. He draws a triangle, and that is his mistake. An oversimplification to explain the base concept. Notice how he also doesn't show any math, or even use the right distance.
@Shandolum22 жыл бұрын
@@YouTw1tFace if the earth was flat, we would have been able to use triangulation to get the distance, but we don't do that. We calculate the distance using 60 nautical miles per degree, which is a spherical distance. And after we have the distance, we draw circles on the globe spherical map to trilaterate the position. Again, this isn't possible on the flat earth, because you don't have a working map with working distances. And my proof, is the fact that not a singular flat earther can do actual celestial navigation without spherical math or the globe spherical map. You can only reference extremely oversimplified and vague explanations, like in this video, where actual celestial navigation is never shown.
@YouTw1tFace2 жыл бұрын
@@Shandolum2 "if the earth were flat" - begging the question fallacy.
@tabletclass11 жыл бұрын
hello; I'm not sure if there was one single person that constructed the book; I suspect the data found in this book was not developed until 1600s as navigators needed accurate time insturments to find Long.....
@brucemacsr.67764 жыл бұрын
Do you remember how good the teacher was when you were taught celestial navigation in officer training? I do. it was bad. Your approach is refreshing. 4.0.
@timfronimos4594 жыл бұрын
Bruce Mac Sr I went through OCS Newport in 1989. When did you go thru training. At some pt in the 1990s this training was discontinued. Only to be resumed ten years later.
@brucemacsr.67764 жыл бұрын
Tim Fronimos Ouch. I’m old guy. I was in NROTC from 1960-64. The Lt. teaching us only had a mechanical knowledge of the subject so it was hard for him to explain the theory and the whys. Two of the guys in the class of 20 or so had to take it again.
@timfronimos4594 жыл бұрын
@@brucemacsr.6776 Funny thing is after all these years, though rusty, I can still fix a position here on the Great Lakes On the occasion that I do get to sail. Thank you for your service to the nation. (hand salute)
@davidjacobson94637 жыл бұрын
Thank you for this incredible "Navigation" documentation. I've just been "getting into it"; so again TY!
@tabletclass11 жыл бұрын
great questions; the more LOP's the more accurate the fix becomes- it's still just one "fix" or position; as to the hemispheres this is determined by which starts you see- i.e. in the S. Hemi you can't see the North Start (Polaris)..final thought: the video was very general but the actual procedure is rather involved and would answer your questions in more detail...
@davecorley55144 ай бұрын
There is a point of diminishing returns. Beyond four LOPs the fix gets less accurate because of measurement errors, instrument errors, plotting errors. Instead of a point fix, the intersection grows to a larger blob. A perfect fix is one in which each fix is taken at precisely the same time with the same sextant and using the same clock that is exactly synchronized to the universal standard cesium clock. A fix with five or six observations taken over five or six minutes while the ship changes speed and course multiple times will generate larger circular error probable (CEP) ellipses. Not good as the ship approaches land.