The amazing thing was that due to the fact that "harrison" was able to build the "H4" he was able to "win" equivalent of multi millions of English pounds by making this extremely simple calculation possible starting at 1:30 ! SO SIMPLE its AMAZING !
One correction here. Meridian passage (noon) at Greenwich is not necessarily 12:00. The almanac will tell you the exact time from which you’ll subtract from Local noon.
Hi Craig , I’m a newcomer to the sextant, I understood the first part but the second part where he had the figures . He had 89degrees 60 , then subtracted 67, 44 but he didn’t explain what the figures were ?
The simplification of the process was very helpful. As an instructive guide, however, you might consider redoing this and show from where the different values shown on your whiteboard came.
Yes I'm totally lost with all the values. What is local apparent noon, or noon sight? Or maybe rather when is it? I mean, is it just you wait until you believe the sun is at the highest point? Sounds rather unprecise already? Then in the latitude calculation, what are the values involved with the calculation. 67 was threading, where do the other two come from?
Years ago when I worked on tugboats going across the Atlantic from the Gulf of Mexico to West Africa towing all rig platform .We used to do those LAN noon sights that you described and at night do a couple positions with Lat by Polaris and jus advance our DR longitude to our current time and generally was within 25 miles . That worked ok until around 10* latitude. This was before gps. And it seemed in the tropics the WX was always cloudy in the evening so star shots were useless. Our towing speeds were about as good as sailboats, slow and slower.
This is the best and most complete video I have found to explain the noon site and it's calculation: to determine geographic location! Thank you so much!
One of the best explanations, in down-to-earth language, of how to acquire Lat and Long, with quick math and the Almanac, EVER! I'm guessing, with an accurate sextant, you're going to be within 30-40 Nm's of your precise location...depending on the actual meridian (or, by not accurately accounting for it). Then again, even with a page of math and the 'navigator's class' on 'long-form', it is highly unlikely you're going to get within 15-miles of precision, anyhow. Long Beach to Hawaii, you're going to know where you are!
89° 60' is just 90° with one of the degrees broken out into minutes to make the next calculation step easier. There are 60 minutes in 1 degree, not 100.@@robertkello7334
I am very glad you post this video . is an effective and simple solution if we are in the middle of no where , and the electronics fail , it happened to me once , after a lighting hit my mast and damage every thing
This is what I was looking for.!!!! I know a bit of the basics(sextant work and Greenwitch time). How to calculate my position roughly with some math. Thanks for posting.!!!!! P.S. I live in the Caribbean, and our sister island is 45 miles away. With a bit clear day, you can see the island.
So, did Frank Worsley, (Ernest Shackleton's navigator), have a time keeping instrument and almanac along with a sextant to be able to guide the failed expedition to get help?
I do not know but there is a method where you use the moon to do all your time keeping calculations. I do not comprehend it but those who can are called Lunarians. Basically, from the moon they get everything without a book or time. Like I said, it’s beyond me but maybe that guy was one of them.
A few tricks to it (I’m pale so I can’t sit in the sun for hours taking an average to figure out noon so I do a single shot at the right time) 1. When the shadow on the lubbers line is pointing north over the compass, it’s time. 2. I know my position and time from yesterday’s noon sight, and I know my direction and speed, so I use Dead Reckoning to estimate when it will be. If I feel like it’s “noon” but it’s the wrong time based on 1 or 2, then I keep waiting. I also set an alarm for 5 min before the predicted noon that way I don’t miss it. All of these factors come together to getting a single noon sight that is close enough to the actual noon that it works well enough for ocean travel.
Great video. It took me a while to understand the subtraction calculation at 06:53. Maybe you need to explain that deeper. 1 becomes 7 by adding 6 instead of the normal 11 it would be in a standard subtraction.
thx for the concise explanation. Quick question re: longitude east and west at the 3:33 minutes mark, you said negative is east and positive west... is this accurate? shouldn't it be the other way around? (negative is west of prime meridian and positive is east of it).
When you do your math, if your noon occurs after noon in England, then you will have a positive number and be West of the Prime Meridian. If you are East of it, your time will be before noon and therefore smaller than 12. When you subtract 12 from it, the number will be negative which tells you that your longitude is East.
Funny how youtube makes this available just after the GGR with Kirsten is basically over. I've been working with a clock, one of the old mini world clocks by SEIKO and the minute I picked it up, looking at wwv, I notice it was only 3 seconds off ! That said, I immediately goofed it up and now have got the little mini manual out so I can get back up on it.
Great video! One question: how do you measure the time of local apparent noon? Do you just repeatedly measure the height of the sun with sextant and then declare after the fact that it has passed after seeing height first raise and then lower again? If so, then the technique explained in this video can be used to find your coordinates only once per day and it requires long enough measurement period to have measurements on both sides of the noon.
Yes, it can only be done once a day, at noon. You can do it the way you mentioned but I found that I was getting sun burnt from the process. To save my pale skin, I would plot ahead with Dead Reckoning and figure out where I think we will be tomorrow at noon and work the math backwards to find the time of Local Noon. I would go sit out in the sun a few minutes before the necessary time and get my sight as the sun would stop climbing. Once the sun stopped climbing, I would wait a few moments and proclaim that time to be my Local Noon. Doing this everyday you begin to get a good feel for when noon is occurring and your longitude gets more accurate, but it puts you in the ballpark of being able to tell if you should see land today or not.
90°00’ is the same as 89°60’ If you start with 90, you will have to convert it to 89 60 as soon as you begin subtracting the sextant reading (unless your sextant value is xx°00’).
Yes it is. But there is most likely an index error To find that sight the apparent horizon and line the two images up to a straight line using the micrometer in whatever direction it takes. The reading on the drum afterwards is the index error. It can be zero, positive or negative. Then sight the sun and apply the index error (with it's sign) on that sight as the first step in the following calculations.
I finely calibrated my sextant to remove all errors in the drum and in the mirrors, so zero is zero. It takes a bit of effort to calibrate the sextant but it then makes all the math so much simpler because there is no error to correct for.
I’m not familiar with that video. This is the method I have been using with great success. It is a method I devised by simplifying the correct method which is much more tedious and time consuming to complete.
Hi, if you wish to calculate LHA then 'East is plus' and 'West is minus '. An example. The GHA of the Sun is 33°, your dead reckoned longitude is 10° East. LHA is always calculated westwards from the observer. 10°E + 33°W = an LHA of 43°.
Thanks for the video. I got the math but the explanation was a bit confusing. You said "when your noon is 10AM". I think it's actually "when your GMT clock reading is 10AM (10:00 UTC)". The local noon is obviously always 12PM. If GMT is behind (earlier time reading) then you are east of GMT, and if GMT is ahead (later time reading) then you are west of GMT.
There are a bunch of methods that you can use such as taking a. Inch and averaging them to figure out when noon actually happened. I just get a feeling that noon is coming and keep an eye on the lubbers line on the compass. When the shadow is pointing N I know it’s soon time. I also throw a little dead reckoning in and figure where I was and what speed I’ve been moving to guesstimate what time noon should occur. All of this comes together to a point where I only do one noon sight at noon and I tend to be within a few miles of our actual position. For finding land while out in the ocean, that’s been good enough.
Very nice explanation. Did we take into account the difference between "Clock" noon and "Solar" noon (meridian passage) or, can we ignore it for practical purposes?
i have a question for anyone that can help, I am trying to read and make placements of Captain Vancouvers log and positioning by his noted longtitute and latitude recordings, but for the most part when i take his numbers and place them into a long-lat finder they are seriously off, is there a way to better locate his recorded numbers to find actual places on a map
I made a spreadsheet that calculates a fix if you put in all the raw data (elevation angle, viewer elevation height, star SHA, etc.). There's a video on my channel describing how I derived the solution with a link to the spreadsheet that you can use.
The method used here for longitude calculations is really easy, but unfortunately can have an error of +/- 4° - which translates to +/- 240 Nautical Mile (+/- 445 Km) error near the equator. If you add the error of noon sights + watch error + sextant errors (index, dip, refraction, parallax) you can easily end up with an error of +/- 300 Nm, which is the distance between the Seychelles Islands and Africa. The good thing is that you can get accurate position with the same instruments.
It can be horribly off by keeping it simple, but if you do it carefully enough and also compare it to your dead reckoning, I have managed to keep it down to just a few miles of error at 5°N. If you think you are 300 miles ahead, land will just take about 3 more days to come over the horizon and you will figure out that you were a tad off 🤣 These are quick calculations. If you find that your position is way off, then other more accurate methods can be employed. Otherwise, the noon sight comes in a few miles from the DR and then you have lunch 😎
Not too sure about the +/-4° error though. Going minute by minute instead of second by second for longitude, the error is only 15’ per minute of time. To be off by +/-4° would mean taking the noon sight 16 minutes before or after LAN. That’s a 32 minute window of time which would naturally make a big area for error, but being careful I keep it down to just a few miles. Knowing when the LAN occurs is more important to longitude than working the sextant.
The method would be perfect if the earth's orbit around the sun would be a circle and and the axis of the earth would be perpendicular to the orbit's plane. But the orbit is ellipsoidal and the axis is tilted - this results that the sun is not always appearing at the highest point at noon. This difference is called "the equation of time" and can be +16 /-14 minutes trough the year. If you are lucky, there are 4 days in a year, when the error is 0.
Hmm. Thanks for that information. I guess my errors in calculations canceled out those errors in time because I was usually within a few miles of my gps position. I will look into this further.
I guess when noon will occur based on my last noon sight and which direction and speed I have been moving. This lets me estimate when noon will occur so I can be ready. I also watch the compass as it has lubbers lines that stick up and cast a shadow. When the sun is at its meridian in the south, the lubbers line shadow will point north (plus or minus the local magnetic variance which is known). All of these clues help tell you when to take the noon sight. I only do one because I’m pale and will burn to a crisp if I sit out in the sun measuring it the correct way where you measure and average the sightings to figure out mathematically when noon occurred and then use that correct time. I always start my plotting when we leave so that I know where I started and can then estimate when noon will occur on each day of the passage. Comparing the calculated position with the Dead Reckoning position helps let you know if you need to look earlier or later when you do your next noon sight tomorrow.
You can’t just use 12:00. Maybe it’s a good approximation in June, but in November the equation of time can be as much as 16 minutes different from mean time. Since you have the nautical almanac open for the daily page to find Dec, just look up equation of time and add or subtract as appropriate from the 12:00. Then it works mathematically when given a hypothetical time of LAN. However, in practice this doesn’t work very well because the sun seems to “hover” in the sky at LAN and is hard to pin down when it actually passes our meridian. This can be up to 3 minutes off, so 0.75 of a degree of longitude which is 45 nm at the equator, less than that at higher latitudes but still significant. There are better more exact ways to estimate longitude at LAN like graphing, granted harder to do and not very practical and that’s why it isn’t done much.
It’s not the most accurate, but at 45nm of error, you are probably going to see more traffic and start getting radio signals from shore to clue you in to the fact that you are approaching land. I managed to get within 20nm of my true position and regularly within 6nm of my true position using this less than accurate method. It’s not perfect but it’s really easy and that makes it more likely to be done. Spotting an island from about 100nm is possible if you can spot the land cloud over it. It’s how we would find islands long before they appeared over the horizon. The goal of this is to be able to find land, and then using other aids to navigation, find your way from there.
hellooo sailors around the wolrd..i do have one question...does it in old time the nautical almanac already existed ? i thought almanac table just exist in modern wolrd...
They are printed yearly and have existed for a very long time.
2 роки тому
worst case scenario, when you miscalculate: you discover the east pole... and it's about time someone does, the other poles got so bored in the meantime, they literally started to melt, just to get some change!
I’ll be making an entire video on it and how to determine it while sailing, but the short answer is: it’s the time when the sun is at its highest position in the sky.
@@RiggingDoctor Hm, that was maybe a bit unprecise by my side. So how do you measure the greatest angle? Do you shoot the sun multiple times around a dead reckoning time?
@@RiggingDoctor Does it involve the angle between the center of the earth and the center of the sun and the line from any point on the earth and the center of the sun?
This is my short hand math for finding your position. Dip, refraction, and eye height are ignored because they complicate the calculation a little and don’t improve the calculations much. Remember, you are taking a sight on a pitching deck. Everything is moving so the sight is imperfect. This is why I also don’t calculate seconds either. It’s close enough to work, easy, and far from perfect.
@@RiggingDoctor Thank you for the clarification. I just ordered a cheap 2022 nautical almanac, and I look forward to testing your "easy, no LOP" method, to see if it works for me. Fair winds. ⛵
Are you as good at fixing teeth as you are at guessing your noon sight? Not bad for a UMD tooth fixer. Fair Winds from the crew of Sv Celtic Lady Seawind II 68 Ketch.
I'm a little confused on the part with the time. You say your local noon is 3:57. Then you add 12 to get UTC. Then you subtract 12 and call the result GMT. wtf?
3:57 PM is 15:57 UTC and the time difference from “my local noon” to “actual noon in Greenwich” is 3 hours and 57 minutes. It’s a positive number so we are West. If it was a negative number it would be East. Imagine that my local noon happened at 8:47AM. In 24 hour time, that would be 08:47. Remember, the clock that we read the local noon from is always set to UTC If we subtract 12:00 from that: 08 : 47 -12: 00 ---- -4 : 47 x15 x0.25 ------ -60°+11.75° Since it’s negative, that means that our longitude is 71°15’E
Remember, the clock you are measuring noon off of is set to UTC but it’s not a 24h clock so we need to convert AM and PM to 24 hour time. That’s the +12 since it was PM.
Didn't see you use the Nautical Almanac to determine latitude when sightings on the sun is at any position (elevation) other than overhead. Inquiring minds need to know.
89°60’ or 90°00’ are the same thing. When you subtract your reading which will be xx°xx’, you will need to reduce the 90°00’ into 89°60’ to finish the math. It just speeds it up a step.
You are trying to find your angle relative to the sun. The sextant gives you one reading, and you need to subtract it from 90°. There is a very complicated method to figure out your position which takes me a while to do it all. This is my “cheat sheet” version. It’s quick and easy and gives you almost the exact same value. To make it work, you start by subtracting your sextant reading from 90° (or 89°60’)
@@RiggingDoctor But you are not showing the conversion. Where is the place in the equation where you decided to subtract 40 minutes from 90 degrees? I thought one simply would use 90 degrees all the time. You simply put 89 degrees and 40 minutes on the screen without showing why you choose those numbers. Please show me where you got those 40 minutes from.
That’s exactly the reason to not try and be super accurate in the math, the boat was rocking so your measurements are not going to be perfect. Close enough is good enough
I'm confused. How does your local noon occur at 1537 hours? or is that time based on UTC? For example. I am on the East Coast of the U.S. UTC -4. Would that make my local noon occur at UTC 0800 hrs?
Exactly. It’s the time of your local noon taken on a clock set to UTC time. If you’re on the east coast of the US and your local noon occurs 4 hours after noon occurs at England, than your longitude would be 4*15=60W and your local noon would occur at 12+4=16:00 Your local noon will occur at some time period around this hour and the minutes of the 16:xx will help fine toon your longitude.
'local noon' is not local 12:00 (well it might be at a particular longitude) 'local noon' is the moment when the sun is locally at its highest point in the sky, this changes with longitude. Your 'local noon' and that of someone a mile down the road are different
I heard the first one fine. I understand the pain of uploading a video, finding something wrong with it and deleting it to upload a fixed version. You lose the views and likes of the first video. So I watched this video a second time, liked and here's my comment to help the analytics so youtube will suggest your content to others 😉
I’m self taught with a lot of challenges in learning. I found the UA-cam series, Practical Navigator the most helpful, but I needed to do a lot more studying, given that I had zero understanding of celestial mechanics before immersing myself in the subject. . There’s nothing easy bout learning celestial navigation. If I knew nothing of celestial navigation, this would be unhelpful. And if I knew celestial navigation, then this video would be unnecessary. Sorry.
Sorry it wasn't more helpful for you. Sextants are easy to use, but the standard math is unnecessarily complicated. My goal was to demonstrate a simplified calculation that is accurate enough for celestial navigation, but still simple enough to do quickly to obtain your latitude and longitude.
@@RiggingDoctor You were explaining a noon sight. Who was your intended audience? If it was a novice, I can’t imagine that you could launch into this without a lot of background I think a lot of graphics would be helpful. Anyhow,I ’m coming off way more critical than I intended. Many have attempted to simplify celestial navigation (eve a noon sight), few if any have succeeded. In a single lesson. Thanks.
@@RiggingDoctor I taught myself how to solve the PZX triangle by watching YT videos. I enjoy seeing how you do it. Will you be taking a sextant on your next passage?
Yes, but the reason you do it is if your local noon is BEFORE 12:00 GMT then you will have a negative result and your longitude will be East Use the same method every time and then you make fewer mistakes when it matters (it's also technically correct)
But also simply explained. It’s easy to do and gets your position to within a few miles of your actual position. If it’s easy to do, you will do it; if it’s complicated to do, you will know how to do it but will never want to do it 😉
This method is basically how Harry Pidgeon navigated his sailboat single handed around the world in the 1920s. Good enough ? Sure but... since Latitude by LAN is good to +/- 3 to 4 miles even with the Davis Mk 15 plastic sextant then why not do a little bit better with longitude determination using timed equal altitudes before and after local apparent noon then split the difference for an exact time to the second of LAN. Looking up this UTC time of LAN in the daily pages of the Nautical Almanac gives a Greenwich hour angle (GHA) that is your longitude to within 3 or 4 nautical miles. en.wikipedia.org/wiki/Harry_Pidgeon
One of the best videos of it's type that I've ever seen.
Thank you so much for all your wisdom. I learn so much and clarify so much from your generosity of sharing.
Your videos are a never ending source for sailing commonsense. Thanks again !
The amazing thing was that due to the fact that "harrison" was able to build the "H4" he was able to "win" equivalent of multi millions of English pounds by making this extremely simple calculation possible starting at 1:30 ! SO SIMPLE its AMAZING !
Brilliant. Thanks for explaining with common sense. Cross referencing with real life you see around you has to be the best way.
As a first-timer and interested in land navigation, I really enjoyed the simplicity of your approach!
Glad to hear it!
Thank you for going To the trouble of cracking the audio issue. It’s even better the second time around.
Ya would be a Great Backup when the GPS is on the Blink 👍 Continue to Stay Safe & Enjoy 😎
One correction here. Meridian passage (noon) at Greenwich is not necessarily 12:00. The almanac will tell you the exact time from which you’ll subtract from Local noon.
Hi Craig , I’m a newcomer to the sextant, I understood the first part but the second part where he had the figures . He had 89degrees 60 , then subtracted 67, 44 but he didn’t explain what the figures were ?
@@sailingthalassa it was the declination from the almanac for the given day/hour
@@theHDRflightdeck thank you , that’s what I was missing .
longitude calculation need to factor in equation of time
Bingo
Great video, thank you! The talking birds had me cracking up.
Fantastic! My favorite kind of video, your tutorials! 🙏🙏❤❤⛵⚓
Audio perfect!! Thanks
The simplification of the process was very helpful. As an instructive guide, however, you might consider redoing this and show from where the different values shown on your whiteboard came.
We will be doing more videos that will go deeper into the small factors that are involved.
Yes I'm totally lost with all the values. What is local apparent noon, or noon sight? Or maybe rather when is it? I mean, is it just you wait until you believe the sun is at the highest point? Sounds rather unprecise already?
Then in the latitude calculation, what are the values involved with the calculation. 67 was threading, where do the other two come from?
Good to know the basics. GPS has really transformed navigation and made it so easy. Hopefully we don't lose this technique.
I love GPS but keep up my paper skills in the event that I find myself without gps one day!
Years ago when I worked on tugboats going across the Atlantic from the Gulf of Mexico to West Africa towing all rig platform .We used to do those LAN noon sights that you described and at night do a couple positions with Lat by Polaris and jus advance our DR longitude to our current time and generally was within 25 miles . That worked ok until around 10* latitude. This was before gps. And it seemed in the tropics the WX was always cloudy in the evening so star shots were useless. Our towing speeds were about as good as sailboats, slow and slower.
You guys are so in touch with reality, and the (Keep It Simple Stupid) KISS mindset!!
Hello I really like this video. The dark background is what I use in some of my videos, looks great. Saludos Iberians
This is the best and most complete video I have found to explain the noon site and it's calculation: to determine geographic location! Thank you so much!
You are very welcome!
Thank you. A brilliant explanation.
i m a solo sailor and got crazy trying to learn astro-calculation in case of emergency, this video is just great
That’s why I learned it as well!
Audio is much better. Even though I still have several questions, I appreciate the efforts and information shared.
We’re going to be making other videos that will go into deeper detail on all the finer points.
Much better with the audio correction!👍👍👍
Very well explained nice one.
Thanks for simplifying this
One of the best explanations, in down-to-earth language, of how to acquire Lat and Long, with quick math and the Almanac, EVER! I'm guessing, with an accurate sextant, you're going to be within 30-40 Nm's of your precise location...depending on the actual meridian (or, by not accurately accounting for it). Then again, even with a page of math and the 'navigator's class' on 'long-form', it is highly unlikely you're going to get within 15-miles of precision, anyhow. Long Beach to Hawaii, you're going to know where you are!
Where did he get the 89 degrees and 60 minutes from. Why did he take 40 minutes from 90 degrees.
89° 60' is just 90° with one of the degrees broken out into minutes to make the next calculation step easier. There are 60 minutes in 1 degree, not 100.@@robertkello7334
My man has a sunburn AND a Parrot. Has the cred. He's advocating some simplicity and not coming off like a handy. Thank you sir.
👍
Very Good one of the best I’ve seen on the subject 😊
Thank you very much
Dude, you just rocked it!!! Thank you.
👍
I am very glad you post this video . is an effective and simple solution if we are in the middle of no where , and the electronics fail , it happened to me once , after a lighting hit my mast and damage every thing
This is an excellent backup to electronics which can be destroyed by lightning
Simplest method I have found yet. Thnx from Mauritius.
You are very welcome!
This is what I was looking for.!!!! I know a bit of the basics(sextant work and Greenwitch time). How to calculate my position roughly with some math.
Thanks for posting.!!!!!
P.S. I live in the Caribbean, and our sister island is 45 miles away. With a bit clear day, you can see the island.
I've been looking at how a sextant can tell you where you are.. as in what the values translate as and after. 5 videos you've helped 😊
Thank you! Glad it was able to finally tell you how to figure it out :)
Thanks again.
Very easy to follow
Thank you
Perfect audio!
Yay!
An perfect example of a UA-cam video where common sense ‘finally’ prevails! I believe Charlie agrees! Well done! 😎👌🏻😁
Thank you!
Thank you
So, did Frank Worsley, (Ernest Shackleton's navigator), have a time keeping instrument and almanac along with a sextant to be able to guide the failed expedition to get help?
I do not know but there is a method where you use the moon to do all your time keeping calculations. I do not comprehend it but those who can are called Lunarians. Basically, from the moon they get everything without a book or time.
Like I said, it’s beyond me but maybe that guy was one of them.
How did you determine exactly when your solar noon is on you boat at sea? Your video said it was at 3:37. What was your marker?
A few tricks to it (I’m pale so I can’t sit in the sun for hours taking an average to figure out noon so I do a single shot at the right time)
1. When the shadow on the lubbers line is pointing north over the compass, it’s time.
2. I know my position and time from yesterday’s noon sight, and I know my direction and speed, so I use Dead Reckoning to estimate when it will be.
If I feel like it’s “noon” but it’s the wrong time based on 1 or 2, then I keep waiting. I also set an alarm for 5 min before the predicted noon that way I don’t miss it.
All of these factors come together to getting a single noon sight that is close enough to the actual noon that it works well enough for ocean travel.
Great video. It took me a while to understand the subtraction calculation at 06:53. Maybe you need to explain that deeper. 1 becomes 7 by adding 6 instead of the normal 11 it would be in a standard subtraction.
I should explain the math more in depth. For this video, it was just “how to do it” without any of the why you do it.
great video, common sense helps sailing
Thanks!
thx for the concise explanation. Quick question re: longitude east and west at the 3:33 minutes mark, you said negative is east and positive west... is this accurate? shouldn't it be the other way around? (negative is west of prime meridian and positive is east of it).
When you do your math, if your noon occurs after noon in England, then you will have a positive number and be West of the Prime Meridian. If you are East of it, your time will be before noon and therefore smaller than 12. When you subtract 12 from it, the number will be negative which tells you that your longitude is East.
Funny how youtube makes this available just after the GGR with Kirsten is basically over. I've been working with a clock, one of the old mini world clocks by SEIKO and the minute I picked it up, looking at wwv, I notice it was only 3 seconds off ! That said, I immediately goofed it up and now have got the little mini manual out so I can get back up on it.
Oh the algorithm
Thanks for knowledge capt. I have a question about determine latitude u wrote -67-44 degree . Whre is coming from? Tks
this is the measurement in degrees he got by taking a site of the sun with the sextant.
Great video! One question: how do you measure the time of local apparent noon? Do you just repeatedly measure the height of the sun with sextant and then declare after the fact that it has passed after seeing height first raise and then lower again? If so, then the technique explained in this video can be used to find your coordinates only once per day and it requires long enough measurement period to have measurements on both sides of the noon.
Yes, it can only be done once a day, at noon.
You can do it the way you mentioned but I found that I was getting sun burnt from the process.
To save my pale skin, I would plot ahead with Dead Reckoning and figure out where I think we will be tomorrow at noon and work the math backwards to find the time of Local Noon. I would go sit out in the sun a few minutes before the necessary time and get my sight as the sun would stop climbing.
Once the sun stopped climbing, I would wait a few moments and proclaim that time to be my Local Noon.
Doing this everyday you begin to get a good feel for when noon is occurring and your longitude gets more accurate, but it puts you in the ballpark of being able to tell if you should see land today or not.
@@RiggingDoctor this is interesting, the reverse math of any longitude will give you the solar noon for that longitude?
At 5:05 where does the 89°60' come from? I think I understand the rest.
90°00’ is the same as 89°60’
If you start with 90, you will have to convert it to 89 60 as soon as you begin subtracting the sextant reading (unless your sextant value is xx°00’).
Is the micrometer drum on zero when you start and which way do you turn it if so thanks
Yes it is. But there is most likely an index error To find that sight the apparent horizon and line the two images up to a straight line using the micrometer in whatever direction it takes. The reading on the drum afterwards is the index error. It can be zero, positive or negative. Then sight the sun and apply the index error (with it's sign) on that sight as the first step in the following calculations.
I finely calibrated my sextant to remove all errors in the drum and in the mirrors, so zero is zero. It takes a bit of effort to calibrate the sextant but it then makes all the math so much simpler because there is no error to correct for.
3:30 but in the old best video named "Celestial Navigation (instruction video)" it says otherwise at timer:23:48. Did I miss something here?
I’m not familiar with that video. This is the method I have been using with great success. It is a method I devised by simplifying the correct method which is much more tedious and time consuming to complete.
ua-cam.com/video/UV1V9-nnaAs/v-deo.htmlsi=qx6uBbSpVUZ7Dpd9&t=1428@@RiggingDoctor
Hi, if you wish to calculate LHA then 'East is plus' and 'West is minus '.
An example. The GHA of the Sun is 33°, your dead reckoned longitude is 10° East. LHA is always calculated westwards from the observer.
10°E + 33°W = an LHA of 43°.
Thanks for the video.
I got the math but the explanation was a bit confusing. You said "when your noon is 10AM". I think it's actually "when your GMT clock reading is 10AM (10:00 UTC)". The local noon is obviously always 12PM. If GMT is behind (earlier time reading) then you are east of GMT, and if GMT is ahead (later time reading) then you are west of GMT.
How do you know when the local apparent noon happenes?
There are a bunch of methods that you can use such as taking a. Inch and averaging them to figure out when noon actually happened.
I just get a feeling that noon is coming and keep an eye on the lubbers line on the compass. When the shadow is pointing N I know it’s soon time. I also throw a little dead reckoning in and figure where I was and what speed I’ve been moving to guesstimate what time noon should occur.
All of this comes together to a point where I only do one noon sight at noon and I tend to be within a few miles of our actual position. For finding land while out in the ocean, that’s been good enough.
How does your local apparent noon take place at 3:57pm?
3:57pm UTC means that the sun is directly over you at 15:37 time in England. From the time difference, you can figure out your longitude
If you know the local time if it is not noon and the UTC time too could you do the same method
Indeed!
Yes, but the local time zone is spread across 15 degrees which could be as much as 1000 miles.
Very nice explanation. Did we take into account the difference between "Clock" noon and "Solar" noon (meridian passage) or, can we ignore it for practical purposes?
The difference between them was used to calculate longitude
@@RiggingDoctor Thank you for the reply...will think about it more
@@RiggingDoctor Oh, ok...will watch again. Thanks for the reply.
i have a question for anyone that can help, I am trying to read and make placements of Captain Vancouvers log and positioning by his noted longtitute and latitude recordings, but for the most part when i take his numbers and place them into a long-lat finder they are seriously off, is there a way to better locate his recorded numbers to find actual places on a map
I was hoping someone would chime in on this as it is of interest to me.
Myself a navigation officer who sailed the globe for past 14 years can surely say that the coordinates in the book is wrong 😊
Hey I can hear you now good going
Woohoo!
I made a spreadsheet that calculates a fix if you put in all the raw data (elevation angle, viewer elevation height, star SHA, etc.). There's a video on my channel describing how I derived the solution with a link to the spreadsheet that you can use.
Very nice!
The method used here for longitude calculations is really easy, but unfortunately can have an error of +/- 4° - which translates to +/- 240 Nautical Mile (+/- 445 Km) error near the equator.
If you add the error of noon sights + watch error + sextant errors (index, dip, refraction, parallax) you can easily end up with an error of +/- 300 Nm, which is the distance between the Seychelles Islands and Africa. The good thing is that you can get accurate position with the same instruments.
It can be horribly off by keeping it simple, but if you do it carefully enough and also compare it to your dead reckoning, I have managed to keep it down to just a few miles of error at 5°N.
If you think you are 300 miles ahead, land will just take about 3 more days to come over the horizon and you will figure out that you were a tad off 🤣
These are quick calculations. If you find that your position is way off, then other more accurate methods can be employed. Otherwise, the noon sight comes in a few miles from the DR and then you have lunch 😎
Not too sure about the +/-4° error though. Going minute by minute instead of second by second for longitude, the error is only 15’ per minute of time. To be off by +/-4° would mean taking the noon sight 16 minutes before or after LAN.
That’s a 32 minute window of time which would naturally make a big area for error, but being careful I keep it down to just a few miles.
Knowing when the LAN occurs is more important to longitude than working the sextant.
The method would be perfect if the earth's orbit around the sun would be a circle and and the axis of the earth would be perpendicular to the orbit's plane. But the orbit is ellipsoidal and the axis is tilted - this results that the sun is not always appearing at the highest point at noon. This difference is called "the equation of time" and can be +16 /-14 minutes trough the year. If you are lucky, there are 4 days in a year, when the error is 0.
Hmm. Thanks for that information. I guess my errors in calculations canceled out those errors in time because I was usually within a few miles of my gps position.
I will look into this further.
Glad to hear so, how would you go about it then?
Hi, sorry for my stupid question but how do I know that the sun is in the highest point? Make more measuremets with the sextant? Thanks a lot!
I guess when noon will occur based on my last noon sight and which direction and speed I have been moving. This lets me estimate when noon will occur so I can be ready.
I also watch the compass as it has lubbers lines that stick up and cast a shadow. When the sun is at its meridian in the south, the lubbers line shadow will point north (plus or minus the local magnetic variance which is known).
All of these clues help tell you when to take the noon sight. I only do one because I’m pale and will burn to a crisp if I sit out in the sun measuring it the correct way where you measure and average the sightings to figure out mathematically when noon occurred and then use that correct time.
I always start my plotting when we leave so that I know where I started and can then estimate when noon will occur on each day of the passage. Comparing the calculated position with the Dead Reckoning position helps let you know if you need to look earlier or later when you do your next noon sight tomorrow.
At local apparent noon shadows will be at their shortest.
It's closer than not having it. 😊
👍
You can’t just use 12:00. Maybe it’s a good approximation in June, but in November the equation of time can be as much as 16 minutes different from mean time. Since you have the nautical almanac open for the daily page to find Dec, just look up equation of time and add or subtract as appropriate from the 12:00. Then it works mathematically when given a hypothetical time of LAN. However, in practice this doesn’t work very well because the sun seems to “hover” in the sky at LAN and is hard to pin down when it actually passes our meridian. This can be up to 3 minutes off, so 0.75 of a degree of longitude which is 45 nm at the equator, less than that at higher latitudes but still significant. There are better more exact ways to estimate longitude at LAN like graphing, granted harder to do and not very practical and that’s why it isn’t done much.
It’s not the most accurate, but at 45nm of error, you are probably going to see more traffic and start getting radio signals from shore to clue you in to the fact that you are approaching land.
I managed to get within 20nm of my true position and regularly within 6nm of my true position using this less than accurate method. It’s not perfect but it’s really easy and that makes it more likely to be done.
Spotting an island from about 100nm is possible if you can spot the land cloud over it. It’s how we would find islands long before they appeared over the horizon.
The goal of this is to be able to find land, and then using other aids to navigation, find your way from there.
Yes, absolutely. Thanks for reply
I am confused with Long. If the LAN is 11 am how do you subtract 12:00 from it ?
You would get a negative number which would mean your Longitude is East.
Negative = East
Positive = West
is there any possibility pf txting you directly ?
The sextant itself can only determine latitude. In order to determine longitude, a time reference and local time are required.
You are correct!
The sextant will help you determine when the Sun is at its highest altitude. You do need to know that.
hellooo sailors around the wolrd..i do have one question...does it in old time the nautical almanac already existed ? i thought almanac table just exist in modern wolrd...
They are printed yearly and have existed for a very long time.
worst case scenario, when you miscalculate: you discover the east pole... and it's about time someone does, the other poles got so bored in the meantime, they literally started to melt, just to get some change!
🤣
Refreshing common sense approach
Thank you
You did not explain what local apparent noon is?
I’ll be making an entire video on it and how to determine it while sailing, but the short answer is: it’s the time when the sun is at its highest position in the sky.
It's simply 90 degrees put into a format easy to do subtractions
How do you know the exact local time of noon if you are underway?
It’s the time when the sextant recorded the greatest angle between the sun and the horizon.
@@RiggingDoctor Hm, that was maybe a bit unprecise by my side. So how do you measure the greatest angle? Do you shoot the sun multiple times around a dead reckoning time?
Make sure you start before local noon, and only dial bigger angles. That is, when the sun starts going down, stop shooting and note the time.
How were the values in the nautical almanac calculated?
That is a topic for another video. There is a lot of math involved in creating a book of tables for our easy reference.
@@RiggingDoctor Does it involve the angle between the center of the earth and the center of the sun and the line from any point on the earth and the center of the sun?
The NA gets its data from the International Earth Rotation Service and the US Geospatial Intelligence Agency.
Thank You Sooooo much for explaining this like a Normal Joe🤤. Btw What brand Sextant do you have? Metal or Plastic
It’s a plastic one by Davis instruments.
This video does not mention corrections for dip and refraction. Nor does it say what the eye height was. Were all these factors ignored?
This is my short hand math for finding your position. Dip, refraction, and eye height are ignored because they complicate the calculation a little and don’t improve the calculations much.
Remember, you are taking a sight on a pitching deck. Everything is moving so the sight is imperfect. This is why I also don’t calculate seconds either.
It’s close enough to work, easy, and far from perfect.
@@RiggingDoctor Thank you for the clarification. I just ordered a cheap 2022 nautical almanac, and I look forward to testing your "easy, no LOP" method, to see if it works for me. Fair winds. ⛵
at 7:05. please explain how you got your answer.
I’m going to be doing a separate video on the noon sight in particular which will go into all that in greater detail.
Where did you get 23 24.7 from, your almanac?
Are you as good at fixing teeth as you are at guessing your noon sight? Not bad for a UMD tooth fixer. Fair Winds from the crew of Sv Celtic Lady Seawind II 68 Ketch.
Haha! Thankfully, the tooth pulling is much more error-free
@@RiggingDoctor That's what CHRIS. CONSTANTINE SAYS
I'm a little confused on the part with the time. You say your local noon is 3:57. Then you add 12 to get UTC. Then you subtract 12 and call the result GMT. wtf?
3:57 PM is 15:57 UTC and the time difference from “my local noon” to “actual noon in Greenwich” is 3 hours and 57 minutes.
It’s a positive number so we are West. If it was a negative number it would be East.
Imagine that my local noon happened at 8:47AM. In 24 hour time, that would be 08:47.
Remember, the clock that we read the local noon from is always set to UTC
If we subtract 12:00 from that:
08 : 47
-12: 00
----
-4 : 47
x15 x0.25
------
-60°+11.75°
Since it’s negative, that means that our longitude is 71°15’E
Remember, the clock you are measuring noon off of is set to UTC but it’s not a 24h clock so we need to convert AM and PM to 24 hour time. That’s the +12 since it was PM.
Didn't see you use the Nautical Almanac to determine latitude when sightings on the sun is at any position (elevation) other than overhead. Inquiring minds need to know.
0:47 I show the nautical almanac
if ya get lost, ya just... pulllin some where and .. ask for directions.. wisdom words of capt. Ron.. lol
Wiser words were never spoken!
When a merchant ship is in sight, call and ask for her position. I call that VHF Sighting :)
Noice 👍
Where does 89degrees 60 mins come from?
90°00’ is the starting number but when you start the subtraction you will switch it to 89°60’. It saves a step which makes the math go faster.
Ok but what is the 89 degrees and 60 minutes, where is that from
89°60’ or 90°00’ are the same thing. When you subtract your reading which will be xx°xx’, you will need to reduce the 90°00’ into 89°60’ to finish the math. It just speeds it up a step.
@@RiggingDoctor yeah but what is it, I got confused cause you pulled it out of know where
You are trying to find your angle relative to the sun. The sextant gives you one reading, and you need to subtract it from 90°.
There is a very complicated method to figure out your position which takes me a while to do it all. This is my “cheat sheet” version.
It’s quick and easy and gives you almost the exact same value. To make it work, you start by subtracting your sextant reading from 90° (or 89°60’)
@@RiggingDoctor so you always subtract it from one of those?
Where did you get 89 degrees, 60 minutes?
It’s the 90°00’ that you start with but converted into what you need it to be for the calculation
@@RiggingDoctor But you are not showing the conversion. Where is the place in the equation where you decided to subtract 40 minutes from 90 degrees? I thought one simply would use 90 degrees all the time. You simply put 89 degrees and 40 minutes on the screen without showing why you choose those numbers. Please show me where you got those 40 minutes from.
a degree is 60 minutes. You seem to be assuming a degree is 100 minutes.@@robertkello7334
I found that 03h 37 min. must be 45 02,28' ...???
[54°15’]
3h*15=45°
37min/60=0.6167*15=9.25 (9°)
45°+9°=54°
9.25-9=0.25*60=15’
54°15’
Thank you l confuised
👍
The problem is, the boat is rocking. 😊
That’s exactly the reason to not try and be super accurate in the math, the boat was rocking so your measurements are not going to be perfect. Close enough is good enough
@@RiggingDoctor Navy 'Signalman' is a rate you'll be interested in.
The first 1,000 people to use this link will get a 1 month free trial of Skillshare: skl.sh/riggingdoctor08211
I'm confused. How does your local noon occur at 1537 hours? or is that time based on UTC? For example. I am on the East Coast of the U.S. UTC -4. Would that make my local noon occur at UTC 0800 hrs?
Exactly. It’s the time of your local noon taken on a clock set to UTC time. If you’re on the east coast of the US and your local noon occurs 4 hours after noon occurs at England, than your longitude would be 4*15=60W and your local noon would occur at 12+4=16:00
Your local noon will occur at some time period around this hour and the minutes of the 16:xx will help fine toon your longitude.
'local noon' is not local 12:00 (well it might be at a particular longitude)
'local noon' is the moment when the sun is locally at its highest point in the sky, this changes with longitude.
Your 'local noon' and that of someone a mile down the road are different
Watched a few times but the bird even tho was a nice touch if you are a pirate it was distracting
Big red bird in the room!
They were survival food .
déjà vu
Besides, if you do get lost, just pull in somewhers and ask directions....
😎 love that movie!!
I bet you just simply asked the bird
A little birdie told me the coordinates
I heard the first one fine. I understand the pain of uploading a video, finding something wrong with it and deleting it to upload a fixed version. You lose the views and likes of the first video. So I watched this video a second time, liked and here's my comment to help the analytics so youtube will suggest your content to others 😉
Thank you :)
So you're saying this won't work on a flat earth??
🤣 exactly
I’m self taught with a lot of challenges in learning. I found the UA-cam series, Practical Navigator the most helpful, but I needed to do a lot more studying, given that I had zero understanding of celestial mechanics before immersing myself in the subject. . There’s nothing easy bout learning celestial navigation. If I knew nothing of celestial navigation, this would be unhelpful. And if I knew celestial navigation, then this video would be unnecessary. Sorry.
Sorry it wasn't more helpful for you.
Sextants are easy to use, but the standard math is unnecessarily complicated. My goal was to demonstrate a simplified calculation that is accurate enough for celestial navigation, but still simple enough to do quickly to obtain your latitude and longitude.
@@RiggingDoctor You were explaining a noon sight. Who was your intended audience? If it was a novice, I can’t imagine that you could launch into this without a lot of background I think a lot of graphics would be helpful. Anyhow,I ’m coming off way more critical than I intended. Many have attempted to simplify celestial navigation (eve a noon sight), few if any have succeeded. In a single lesson. Thanks.
@@RiggingDoctor I taught myself how to solve the PZX triangle by watching YT videos. I enjoy seeing how you do it. Will you be taking a sextant on your next passage?
erm
Fixed the audio!
Lose the bird
No…
Too loud..
I had to.
Lol 😜
Step 1 convert 3:37 to 15:37
Step 2 subtract 12:00 so you have 3:37 AGAIN
🤯🤣
Yes, but the reason you do it is if your local noon is BEFORE 12:00 GMT then you will have a negative result and your longitude will be East
Use the same method every time and then you make fewer mistakes when it matters
(it's also technically correct)
Latitude equation is badly explained
But also simply explained. It’s easy to do and gets your position to within a few miles of your actual position.
If it’s easy to do, you will do it; if it’s complicated to do, you will know how to do it but will never want to do it 😉
I used to work a fishing trawler and use the electronics for navigation. This is the best thing I've seen since radar and channel markers. 👍🧭😊👍
👍
This method is basically how Harry Pidgeon navigated his sailboat single handed around the world in the 1920s. Good enough ? Sure but... since Latitude by LAN is good to +/- 3 to 4 miles even with the Davis Mk 15 plastic sextant then why not do a little bit better with longitude determination using timed equal altitudes before and after local apparent noon then split the difference for an exact time to the second of LAN. Looking up this UTC time of LAN in the daily pages of the Nautical Almanac gives a Greenwich hour angle (GHA) that is your longitude to within 3 or 4 nautical miles. en.wikipedia.org/wiki/Harry_Pidgeon
There is plenty of room for improvement! This is just a good starting point that can get you to within sight of land.
My man has a sunburn AND a Parrot. Has the cred. He's advocating some simplicity and not coming off like a handy. Thank you sir.
😎 just living my best life in the simplest way.
Lose the bird
She’s in our lives forever!