วีดีโอ

Well Tenth definitely saw it, because he reacted on the live show shortly after. He was even about to post a link to it in the chat when Nathan jumped in and stopped him and refused any review or further discussion. I was then banned from the server shortly after. I might have struck a nerve. 😆

There are two reasons why angles closer to the zenith are not idea. One is simply that the angle of the index mirror gives less visible area to work with, which makes sights more challenging. The other is that you are dealing with a much smaller circle of equal altitude, which means more error in your lines of position since the tangents will diverge from the circle more quickly.

The vernier scale is in fifths of an arcminute. If the top line on the right side of the vernier is not perfectly lined up with an arcminute line, count down until you find the one that is lined up. For each count, add 0.2 arc minutes to your total. If you bought a used Davis sextant that did not include a user manual, you can download a PDF from the DavisInstruments website. It has pretty good instructions on calibrating and reading your sextant and even includes instructions for doing a meridian passage position fix.

Before the creation of nautical almanacs and sight reduction etc, celestial navigation was mostly limited to using a few key celestial bodies to determine latitude. The invention that really ushered in the more 'modern' era of celestial navigation was portable, accurate clocks. To learn more about that, read about the Scilly Naval disaster of 1707, the 'longitude problem' that led to it, and how clock maker John Harrison was inspired to solve it.

Yes thank you for getting back with answers!​@@protothad837

I have watched on DVD from library the mini series "Longitude " with Jeremy Irons.

I agree, my C.Plath is a far better sextant and still working great even after decades of use. I recommend the Davis mostly as a inexpensive learning tool, because even if the accuracy is not quite as good, the basic operation is the same. I've managed pick up several for less than $100 on ebay to use in the classes I teach. I've not had an opportunity to try some of the newer aluminum Chinese models, but I plan to (and I'll do another review video when that happens).

*The real story is the globe is a stereographic projection of the sphere of the stars* Get AN education, kid. And maybe a psychiatrist. You're not well. *All navigation using the latitude and longitude is always going to show the presupposed sphere* Of course. The Earth is spherical. *The whole world will need to be remapped* Why? Are people getting lost? Are airplanes and ships not getting to their destinations? Aren't our current maps WORKING? Oh, they are? So, as it seems, they're correct. And you're butthurt. *Shane St. Pierre has shown the deception* You're getting indoctrinated by worthless con artists on social media, buddy. *The curve is an effect of optics* Yes. The curve is something we can see. The effect is called reflection: light reflects off of a surface and gets into our eyes so it can be converted into an optical signal to be interpreted by our brains. No different than the effect that we see from everything else.

Go explain Foucault's pendulum with toridal magnetic plasma fields why don't you. Raphael, above, handed you your oversized arse. L O S E R.

Too bad Shane St. Pierre can't actually explain how his.. I mean Bislin's joke FE model, could actually match reality.

@@extrajay4868 Are you blind? Because the model shows it , so why would you need it explained. I'm sorry , I forgot you were a glober , I'll fetch the Special teacher , you put your helmet back on , ok?

@@Heracles_FE Yeah, it shows how ridiculous it is. Distances between latitude and longitude don't even work. Draw a line showing the path of light from the sun to someone seeing it due south from 80s in Antarctica in Dec. Shane won't do it, maybe you can. Space commas... the mark of a true flerfer who didn't even listen to their own special teacher in special ed.

Oh thanks for your personal opinion, kid, but it's still irrelevant.

Didn't watch the video or just didn't understand it?

Then show us how celestial navigation works on Flatopia! Actually do it just like Proto Thad. Make a video so we can learn. Show how the distances between Paris, New York City and Lima work on a flat surface. This could be very instructive!

"The "Globe" was created to map oceans and land for navigation purposes, doesn't mean it is that shape" You're joking , right?? How far did you get in school?

Buh bye flerfaroo, go back to mum's basement.

I appreciate your candor, and yes, I should probably be less sarcastic and more charitable in how I deal with others, even when (perhaps especially when) they fail to behave similarly. God bless.

You must have missed that the claims of flat earthers being discussed here are beyond ridiculous. Essentially grade schoolers arguing that 2+2=5 with people who can do calculus. Thad is an expert in celestial navigation. He mentions all the other people who have demonstrated how celestial navigation shows how it is impossible on a flat earth. So this video has a certain tone to it. One born of exasperation with endless "nuh-uhs" from the flerfers. The tone is very deserved, and to most observers, well merited. I fail to see ANY "lack of sincerity coupled with an abundance of pride" in it. That comment is far more appropriate to the 2+2=5 flerfers addressed in the video.

Very well put

The trick has been found, my friend. Shane St. Pierre has mathematically proven that the sphere is an effect of optics. The globe and the latitude/longitude are based on transposition of the sphere of our vision onto the stars , then sterographically projecting it onto a spherical map. All of it is explained with citations . Shane has made an interactive model that allows you to place an observer anywhere on earth, and all celestial observations are 100% accurate. Shane St. Pierre will not block anyone , and welcomes anyone with knowledge to come and learn how they were deceived by the math.

@@Heracles_FE *Shane St. Pierre has mathematically proven that the sphere is an effect of optics* What's really going on here: you don't know mathematics. You dropped out of kindergarten. So you can't inquiry St. Pierre's work. You're unable to do that. You just believe it. That's how charlatans take advantage of people's ignorance in order to fool them. *The globe and the latitude/longitude are based on transposition of the sphere of our vision onto the stars , then sterographically projecting it onto a spherical map* Our view of the stars are already only possible on a globe, son. That's how we observe reality. Do you know what's latitude? Explain to me what are latitude angles, please. Don't forget to provide the vortice for latitude angles. *All of it is explained with citations* Which you don't understand either, I assume. *Shane has made an interactive model that allows you to place an observer anywhere on earth, and all celestial observations are 100% accurate* That's called a globe, son. You can also check Walter Bislin's model of the "Flat Earth Dome Model". All mathematically shown what light should do on a flat Earth to match observations. Too bad it's kinda like believing in magic.

@@Heracles_FE "Shane has made an interactive model that allows you to place an observer anywhere on earth, and all celestial observations are 100% accurate." So Shane should be EASILY completing MCTOON's 10,000 smackers challenge!!!! And yet, hasn't happened has it? Real life ain't for you kid, you're a big ass loser.

I've actually done that, and it resulting in the fix being about 450 nautical miles off. I show that about nine and half minutes into my 'Correcting Brian's Logic' video. 😎

@@protothad837 brilliant. I missed that one. Off to watch. 👍

What are you trying to say?

Sorry, the 'rest of the stars' can't be see all over the world. I can't see polaris and the most northerly constellation from my home location at 32degrees south and I am currently at about 27degrees north and could not see the most southerly constellations last night. It helps if you actually look.

Sorry should have added that I have tried to see Polaris when south of, but close to the equator and you can't. That does not make sense on a flat earth but it does on a spherical one. For confirmation I tried in 2023 from Africa and a few weeks ago from South America. Got the result you would expect from a spherical earth both times.

​@GiveMeSpaceTravel-bg8td That is an assumption with no basis in reality. You can not see forever, and things go down in apparent location as you move away from them. The only reason you would ever assume that Polaris would not act the same way everything else you see acts is because someone told you it was quadrillion of millions of miles away. So , if you assume a whole bunch of unprovable things , then that belief of yours makes sense, but if not ?

@@Heracles_FE *The only reason you would ever assume that Polaris would not act the same way everything else you see acts is because someone told you it was quadrillion of millions of miles away* Incorrect. Polaris is very close to the north celestial pole, which corresponds to the Earth's rotational axis. Its declination is more than +89°. This has to do with ANGLES, not distance. That's why its circlular path around the actual north celestial pole is very short. All the stars in the north celestial pole (including Alpha Ursae Minoris, aka Polaris Borealis) do the same: they rotate counter clockwise around the north celestial pole; *and all the stars in the south celestial pole (including Sigma Octantis, aka Polaris Australis) do the same: they rotate clockwise around the south celestial pole.* That's exactly what's expected on a globe, son. *if you assume a whole bunch of unprovable things* Things you don't like and don't understand are not necessarily "unproven things", kid.

My attempts to get my sailboat to reach orbital velocity have indeed been unsuccessful. You need really good wind for that I expect. 😜

@@protothad837 LOL!!!!!! Have you tried an asymmetrical? Maybe some foils...

A liquid bending? That's crazy.

Ship Model Basins are full of bendy water thus proving the globe. Globe confirmed 💯🌎

@@awatt only god could talk things into being, apparently. So your words don't count. Are you confusing wavey water, with bendy, curvy water? 😂🙄

@@mightyatom1404 Water visibly curves in Ship Model Basins just as God intended. Globe confirmed 💯🌍

@@awatt only when contained, a bit like cerebral fluids, around a topographic surface. Do you have any? 🙄🤡🌎

None of them did too well on McToon's $10,000 celestial navigation offer.

They also say that a sextant can't work over a curved surface therefore they can't work at sea due to waves.

Get education.

Get a clue.

Earth is FAT.

​@@rafaelmarangoniThat would be , get an education , and education is indoctrination. One can use science to prove the earth is flat.

@@Heracles_FE This is my second language, but sorry if I won't take grammar tips from a person who thinks that education is indoctrination (also because that's not a mistake, but just unusual) and didn't even realize one got indoctrinated by con artists on social media into believing the Earth is flat, buddy. But if you prefer the other way, try getting an education, then. You haven't done that yet. You didn't have that experience yourself. *"You just believed what you were told"* regarding that experience. Sounds familiar?

Do you feel special? You are the one so triggered by someone questioning what you believe , it seems as though you actually don't understand why you believe it and get a bit anxious when someone else voices those thoughts. Trust your gut buddy, they did deceive you. All of this celestial navigation is a shell game . They merely took the apparent sphere of the sky which is an effect of optics being non euclidean , and they projected that onto the planer earth.

@@Heracles_FE *Trust your gut buddy, they did deceive you* Your gut is neither a precision instrument, nor is it omniscient and innately understands laws of nature. That's why you were deceived by con artists, kid. *They merely took the apparent sphere of the sky which is an effect of optics being non euclidean , and they projected that onto the planer earth* People know about the shape of the Earth way before we mapped all the Earth. Get a psychiatrist, kid. You're not well.

@@Heracles_FE You never navigated. You can't leave mum's basement cuz reality keeps slapping your oversized arse. And again Rafael slaps you silly.

Here's the flat earther that found the deception, Shane St. Pierre . Go to his channel and see how they deceived you.

@@Heracles_FE You got deceived by Shane St. Pierre.

@@rafaelmarangoni oh , really? Tell me how exactly.

@@Heracles_FE Easy: you dropped out of kindergarten; you didn’t learn anything useful, like maths, physics, astronomy, geography, etc.; by not having done that, you’re incapable of realizing when a trickster is playing you for a fool; although you don’t know anything about almost everything, you wish to be smart, but without all the effort it takes to make yourself a smart person; so you fall to tricks performed by charlatans on social media so you can have a sense of possessing a “special knowledge”, that the people who actually went to school “ignore”; so you believe anything those charlatans will tell you, in order to feel that way about yourself, even though those charlatans NEVER produced anything useful in favor of humanity, and can only record videos from their mom’s basements on social media. Sounds about right?

@@rafaelmarangoni 🤣🤣🤣🤣 So , just as I expected , hand wave dismissal and nuh ah. What a freaking joke you are. Pseudo iteligentia .

Sorry to hear about your negative experience. The objective lens is held in place by a plastic ring with a press-tight fit. If the ring is missing you should still be able to glue the lens into place. Given that so few people nowadays buy a sextant I can understand that Davis might have parts issues.

So in this new sidebar, the olde' "Periscope CN film" popped up! It starts out slowly removing cobwebs, then starts going full gallop. I can see immediately where Mr Ten confuses flat with/by the film's inclusion of a ground mock up using a pole, circle and movable hypotenuse. It's just a graphic. I'm sure this same graphic has been immortalized throughout cyber lol. But the Divergent personage? That's kinda' odd.. Cheers! (I'm number 565)

"Please answer each as I have a follow up." Who cares about your "follow up", your questions bring the lolz!

Interesting questions. I'll answer them one per comment. I look forward to your follow-up questions. 🙂

ANSWER 1) Latitude lines are not just based on elevation angles to Polaris. That is one way to approximate your current latitude, but because Polaris is slightly off center from the celestial north pole, and because refraction does indeed add some error when measuring near the horizon, other methods provided a better method of establishing the overall arrangement of latitude and longitude. Observations of a great many stars contributed to our system of navigation. The ground position of each star travels a precise east to west path, tracing a full line of latitude once per sidereal day. By using something called a zenith sector to observe when a star passes directly overhead, we can measure both the path and size of that latitude line. This has the advantage of eliminating refraction based errors (refraction drops to zero as your sight line approaches the zenith). This method establishes not only the latitude line, but the relative scale of longitude at each latitude... which confirms the spherical shape of the earth.

ANSWER 2) Yes, if you surface and climb out onto the deck or conning tower, you can use a sextant to do celestial navigation on a submarine. It works no different than on any other ship in that case, so you still have to do dip correction. It is technically also possible to do celestial navigation via the periscope, but in that case you sight directly on the star and NOT the horizon, measuring the co-altitude directly from the vertical much like you would using a bubble sextant. In truth, modern submarines navigate via inertial guidance, sea floor mapping, and other methods that do not require them to surface.

ANSWER 3) In theory the dip correction is zero at an elevation of zero, but only because at that point the horizon is literally sloshing against your eyeball. In reality, we never do celestial navigation with our face in the water. Indeed, since refraction gets far worse close to the surface of the water, it is best practice to take sights from well above the surface. There would be virtually no dip correction on a flat earth, because the laws of perspective dictate that a flat, not curving surface will converge toward the vanishing point at your eye level. We can work through the geometry of that if you like.

Look more closely at the image. The green line is clearly not the surface. The surface is that curving thing below the green line. Your claim that a flat surface is needed is just a begging the question fallacy... a flat earth belief you've never put to the test by doing any actual celestial navigation. But I'm still willing to help you with that whenever you decide to move past parroting silly talking points. Who knows... you might actually have fun. It may even change your whole worldview. 🙂👍

It's not begging the question because you used 90° to get the distance on the surface from the ground position of the star. ​​How do you get 90° on a sphere ​@@protothad837?

@@TB-xx8vj How do we get 90°? It's pretty obvious when you just look at the diagram. The surface is never a line in our angle. The 90 degrees is just the difference between vertical and horizontal. Horizontal is a line projected from our eye. It. Is. Not. The. Surface. Your assumption that the surface is a line in our angle is just a... (drum-roll please)... Begging the Question Fallacy. 😎

​@protothad837 The begging the question fallacy is the circle you drew underneath the horizontal plane that you use to get 90° for calculating the distance from the ground position of the star. You have proven that you need a flat earth for celestial navigation.

@@TB-xx8vj _You have proven that you need a flat earth for celestial navigation_ If it also works with the circle underneath, then why are you begging the question by assuming that it's flat?

There's no such thing as a 'flat earth' elevation angle. Elevation angles are measured relative to horizontal, not the surface. Perhaps you should actually watch the video? 🙂

A horizontal baseline to measure elevation angles of stars is a flat earth. You need a flat earth for latitude on the surface. So it's silly to say the horizontal baseline is not the surface. Similarly, you need a horizontal plane for azimuth angles to get longitude on the surface.

Here's a good question. Why don't they use a globe on ships,​@@protothad837? Is it because it doesn't work? 😂

@@TB-xx8vj No, it's just a dumbass question typical of a do nothing incompetent like you.

@@TB-xx8vj Latitude and longitude do not work on a flat earth. The longitude scale always matches the cosine of latitude, getting narrower both north and south of the equator (matching a sphere... not flat surface). This is reflected in every navigation chart, plotting sheet, and the very process of navigation itself. This might become clear to you if you make an effort to set aside your confirmation bias and actually think about what this video is showing you... and especially if you try the process for yourself.

It is not even new technology. I think I remember reading an article a while back about the U2 spy plane having something like that.

As far as I know, no flat earther's were in attendance. I keep offering to teach them... but they seem happy just argue about angles without progressing to actually doing any cel nav for themselves. 🤷‍♀

It's 100% dishonesty. Maybe stupidity factors in there somewhere.

No, that was a more recent sail on a 29 ft Catalina on Lake Michigan... one of the boats in the sailing center's fleet.

Hi Petey, Brian's brain cell will have exploded by now!

@@marcg1686 😆

@@marcg1686 debatable if he even had ONE.

LOL!! A four hour debunk where not a single fact will be uttered.

Great! Another opportunity to kick Brian around!!!

I was tempted to hold off and release this video on the anniversary of the initial 'Response to Tenth Man' video as another Christmas present to that crew... but ultimately this is not really a video aimed at flat earthers, just anyone interested in cel nav... so Merry Christmas! 🙂