Thank you for posting this series of videos. Your method of instruction is the best I have found in regard to this subject. I had gotten away from this type of navigation for quite a while & I had forgotten most of what I had previously known. This series brought it all back pretty quickly & then moved me further forward than I had been before. Your request, for those of us learning from you, to now pay it forward to other people, is taken well to heart. If I can find interested individuals, I will do my best to make that happen. I believe that this is a valuable knowledge base to preserve for future generations.
Hey Chris, thanks very much. I made it through the entire course and learned a great deal about celestial navigation; a subject of which I had no previous understanding. On the way I learned a lot about basic astronomy and the movements of the celestial bodies. This had always been a complete mystery to me until I watched your videos as well as studying numerous sources on the Internet and books, as well. This has been a very fulfilling experience. Thanks again
Not sure if you’re still looking at comments on these older videos, but your request at the end to teach this stuff to others stuck with me. I am currently teaching a small elective celestial course on the side at my university. Thanks for your great work in these videos, and for the inspiration.
Thanks Chris I learned alot from your videos. Im a seafarer and celestial navigation is one of my weakness and mostly seafarer always depends on the gps nowadays. We have this lecture at college but never really understand it.
Great course, Chris! Thanks for going through the effort to post these videos, you've got real talent as a teacher. Now, I just need to get that background music out of my head, ha ha.
+spelunkerd Thanks for the questions, it looks like you made great progress through the series. Sorry about the music...Apple only has so many background tracks that seem to fit doing math problems! I thought about using some K-pop, but this jingle fit a bit better :)
Hey Chris, really appreciate you putting together these videos. I'm a sailor but a complete novice at celestial navigation. Your videos make it really easy to grasp the concepts, and I've learnt a lot very quickly. Very best of luck with your return to duty. P
Thanks Chris for the amazing video series, I did the whole thing! I've skirted around celestial navigation for years, but you've got me tuned in. I'm about to make passage from Baja to Hawaii, provision, top off the tanks with fuel and water, then sail to Majuro in the Marshall Islands.....guess what I'll be practicing! as they say Komool tata brah lol seriously thanks Chris! Hey if you're ever in the Marshalls, look me up and I'll buy you a few beers! - Henry
Thanks Chris your videos helped me get through my YM Ocean Theory that I'm doing online. Wouldn't have been able to complete the course with out your excellent videos to guide me through challenging sections.
Hi Chris, brilliant , comprehensive series on astro nav, I thought for a second, when looking at the title, that you were covering longitude by lunar distance. LOL.
Hi Chris, what if your lost at sea for a week or two with no break in the clouds. You can only use dead reckoning and you fear you may have blown of course by hundreds of miles. How far can you be off by dead reckoning and still get an accurate fix once the clouds break and you are able to resume celestial navigation. And why do you have to have a somewhat accurate notion of where you are in the first place, since the whole point of the intercept method is to tell you exactly how fare your LOP is from your assumed position. Thanks.
+lisarob5767 LisaRob, great question - this was the crux of early navigation. Even worse, imagine if we knew nothing of ocean currents and effects of winds...we would be well off course! The good news is as soon as you see an object, you can correct your position without ill effect. I think what you might be referencing is if the Assumed Position was much farther than you thought it was...in that case, you would notice that your "towards" or "away" would be like 60-100 nautical miles...in that case, it could work, or to be more accurate you could re-do the calculation with a better AP. The necessity for accuracy in the AP is more to do with the fact that any LOP is just a tangent from a circle of equal altitude. Although your tangent would be ok even if you were 100nm from the AP, it's accuracy decreases with distance to the left or right. Might be confusing you here, but any AP will work...but the closer you get, the more accurate your final LOP will be, particularly perpendicular to the azimuth line. Thanks for the question!
+NavigationTraining I got lost in your last several sentences. Can u try explaining again. Illustrations might help, but I don't think you can do that in the comments section. Thanks.
+lisarob5767 No problem - try this: If you can fix your position with two objects, the distance to AP really doesn't matter. However if you are just working with one object, if your AP is fairly close to your actual position, when you draw the celestial line of position, you are drawing a tangent to the actual "circle of position." On a global scale, if you plotted everywhere on earth where you saw the sun at say...50 degrees above the horizon, it would trace a giant circle over like 1/3 of the earth. This is a circle of equal altitude - the altitudes are equal all along it. Zooming in to your little part, your azimuth line points to the center of the circle (maybe half a world away), and your celestial Line of position is perpendicular to the circle of equal altitude, or a tangent. So the closer your AP is to the actual line of position, the better, because if it is very far away, then the curvature of the earth means your line is not actually a straight line, but rather less accurate. But this inaccuracy is fairly small, especially if you are in an emergency. So bottom line, if you are lost and then the clouds break - getting anything on paper is good, you can use it as a first approximation and then try again as able. Hope that helps!
Hi Chris, I see where the nautical almanac shows the moon’s meridian passage. I assume you can use this for a daytime moon sight similar to a noon sun sight. Is that’s so, why have I not heard anyone talk about it. One could get the equivalent of noon sight in the morning or the afternoon depending on when a daytime moon culminates.. On another issue, I have recently been looking at the air almanac. It seem simpler-less interpolation, no hp’s to deal with (with a simpler moon corrections on each page}, no v or d values to deal with, and no need to deal with 0.1 of miles which is likely beyond most person’s ability to accurately determine in the firs place. Just wondering about your thoughts on these issues. Thanks much.
That was all for sea level navigation. Can one do this on the Great Lakes, which are not at sea level? The altitude of these lakes are different and changes due to season and weather. How can we account for this varying water level?
It works for large lakes where there is a horizon to get the level. If the shore is visible, then there is no accurate level reference line. You can even use a bowl of liquid (water, oil, mercury) as overland explorers used to do.
@@karhukivi If you do the bowl of water trick, you need to divide the measured angle by two after correcting for index error. In this case, there is no correction for limb choice, as you just superimpose the two identical images upon each other. Most sextants will not have enough range of adjustment to measure an object that is much more than 65 degrees above the horizon due to the doubled angle of measurement, so summer time noon sights in lower latitudes become unavailable, but accuracy with this method tends to be excellent. It often helps to put a piece of glass or saran wrap over the bowl to keep wind from disturbing the water's surface.
@@youtubeleavemealone I use a Davis "artificial horizon" which has sun filters that also keep the wind out. Instead of water I use propylene glycol which does not leave condensation on the filters and is somewhat more viscous than water. The Davis Mk25 sextant can superimpose images but otherwise it is easier to use upper or lower limbs, especially for the moon when it is only partially illuminated. Depending on one's latitude, summertime noon sights can be beyond the range of the sextant, but I use morning and afternoon sights to get a position and the angle is usually within range.
@@karhukivi The Davis artificial horizon is nice for a few reasons. It uses angled glass, which prevents you from confusing glass reflection with water reflection. It comes with shaded lenses so that you don't blind yourself looking for the sun's reflection & it packs up small for easy back packing. I manage to superimpose images on a split screen MK15 as well as a MK 25. For me it works well. Personal preferences may vary. On a genuine horizon, I do use the lower limb of the sun, as is traditional.
@@youtubeleavemealone Yes, it is a neat device. I use propylene glycol, the liquid base used in vaping liquids. It's non-toxic, has a high boiling point and a low freezing point, as well as being somewhat viscous, so it's better than water. It is soluble in water too, so easy to clean. a 1L bottle cost me $10 from a vaping supplies shop.
Navigator Chris has outlined the proceedure for Apparent Altitude correction of Moon sights. He advises to spend some time with the tables. There is a useful but slower paced explanation for this task starting at moment 09:02 on Andy Howe's channel "The Nav Station" Episode #14. If i can get the link typed in correctly and if the UT police leave things in peace !! ua-cam.com/video/hrmqS2-p85Q/v-deo.html Hope that helps anyone needs an extra input on this correction. Cheers . John R.
Many thanks for making this excellent series - I hope it inspires lots of sailors to turn away from their GPS sets and start using a sextant. I wrote my book 'Sextant' with exactly the same aim, though it's not a 'how to' guide. It's part personal memoir, part history and part science - with many examples of great voyages guided by the stars, from Bougainville and Cook to Slocum and Worsley. In case you want to read it, it's published by William Morrow in the US and William Collins in the UK. There is also a new Italian translation and a German one is due out in 2015. Good sailing! By the way, I'm promoting these videos as best I can:@sextantnav as well as 'sextantbook' on Facebook and Tumblr.
I read your book as a pandemic diversion; nice job! I hadn’t fully understood that the lunar distance method emerged around the same time as the chronometer, and how these tools complemented one another for so long.
Wesley Burghardt Many thanks Wesley. I’m glad you enjoyed it! You might possibly also be interested in my latest book, SUPERNAVIGATORS which is about the science of animal navigation. More details on my website davidbarrieauthor.org. Best wishes David
Thank you for posting this series of videos. Your method of instruction is the best I have found in regard to this subject. I had gotten away from this type of navigation for quite a while & I had forgotten most of what I had previously known. This series brought it all back pretty quickly & then moved me further forward than I had been before. Your request, for those of us learning from you, to now pay it forward to other people, is taken well to heart. If I can find interested individuals, I will do my best to make that happen. I believe that this is a valuable knowledge base to preserve for future generations.
I can't believe that this video has 12k views & only 153 likes. That's just not right.
Hey Chris, thanks very much. I made it through the entire course and learned a great deal about celestial navigation; a subject of which I had no previous understanding. On the way I learned a lot about basic astronomy and the movements of the celestial bodies. This had always been a complete mystery to me until I watched your videos as well as studying numerous sources on the Internet and books, as well. This has been a very fulfilling experience. Thanks again
Not sure if you’re still looking at comments on these older videos, but your request at the end to teach this stuff to others stuck with me. I am currently teaching a small elective celestial course on the side at my university. Thanks for your great work in these videos, and for the inspiration.
Awesome to hear that Wesley, good luck in your teaching!
Thanks Chris I learned alot from your videos. Im a seafarer and celestial navigation is one of my weakness and mostly seafarer always depends on the gps nowadays. We have this lecture at college but never really understand it.
Great course, Chris! Thanks for going through the effort to post these videos, you've got real talent as a teacher.
Now, I just need to get that background music out of my head, ha ha.
+spelunkerd Thanks for the questions, it looks like you made great progress through the series. Sorry about the music...Apple only has so many background tracks that seem to fit doing math problems! I thought about using some K-pop, but this jingle fit a bit better :)
Hey Chris, really appreciate you putting together these videos. I'm a sailor but a complete novice at celestial navigation. Your videos make it really easy to grasp the concepts, and I've learnt a lot very quickly. Very best of luck with your return to duty. P
Hey Chris thank you very much. As Matthew said you are such an amazing instructor.
Thanks Chris for the amazing video series, I did the whole thing! I've skirted around celestial navigation for years, but you've got me tuned in. I'm about to make passage from Baja to Hawaii, provision, top off the tanks with fuel and water, then sail to Majuro in the Marshall Islands.....guess what I'll be practicing! as they say Komool tata brah lol seriously thanks Chris! Hey if you're ever in the Marshalls, look me up and I'll buy you a few beers! - Henry
Hi Henry - glad it was useful and thanks for your comment - jealous of your upcoming trip!! Sail safe :)
Thanks Chris your videos helped me get through my YM Ocean Theory that I'm doing online. Wouldn't have been able to complete the course with out your excellent videos to guide me through challenging sections.
Hi Richard, that is such excellent news, congratulations! Great to hear it is being useful. Happy navigating :)
Hi Chris, brilliant , comprehensive series on astro nav, I thought for a second, when looking at the title, that you were covering longitude by lunar distance. LOL.
Great videos! Same for me, I am doing it for personal satisfaction and experience as well! Kinda hobby like! It is much fun too!
Narration Moves
To fast through discussion and slides.
Carl, i have added a link to help with this Apparent Altitude correction Its above.
Cheers John
Hi Chris, what if your lost at sea for a week or two with no break in the clouds. You can only use dead reckoning and you fear you may have blown of course by hundreds of miles. How far can you be off by dead reckoning and still get an accurate fix once the clouds break and you are able to resume celestial navigation. And why do you have to have a somewhat accurate notion of where you are in the first place, since the whole point of the intercept method is to tell you exactly how fare your LOP is from your assumed position. Thanks.
+lisarob5767 LisaRob, great question - this was the crux of early navigation. Even worse, imagine if we knew nothing of ocean currents and effects of winds...we would be well off course! The good news is as soon as you see an object, you can correct your position without ill effect. I think what you might be referencing is if the Assumed Position was much farther than you thought it was...in that case, you would notice that your "towards" or "away" would be like 60-100 nautical miles...in that case, it could work, or to be more accurate you could re-do the calculation with a better AP. The necessity for accuracy in the AP is more to do with the fact that any LOP is just a tangent from a circle of equal altitude. Although your tangent would be ok even if you were 100nm from the AP, it's accuracy decreases with distance to the left or right. Might be confusing you here, but any AP will work...but the closer you get, the more accurate your final LOP will be, particularly perpendicular to the azimuth line. Thanks for the question!
+NavigationTraining I got lost in your last several sentences. Can u try explaining again. Illustrations might help, but I don't think you can do that in the comments section. Thanks.
+lisarob5767 No problem - try this: If you can fix your position with two objects, the distance to AP really doesn't matter. However if you are just working with one object, if your AP is fairly close to your actual position, when you draw the celestial line of position, you are drawing a tangent to the actual "circle of position." On a global scale, if you plotted everywhere on earth where you saw the sun at say...50 degrees above the horizon, it would trace a giant circle over like 1/3 of the earth. This is a circle of equal altitude - the altitudes are equal all along it. Zooming in to your little part, your azimuth line points to the center of the circle (maybe half a world away), and your celestial Line of position is perpendicular to the circle of equal altitude, or a tangent. So the closer your AP is to the actual line of position, the better, because if it is very far away, then the curvature of the earth means your line is not actually a straight line, but rather less accurate. But this inaccuracy is fairly small, especially if you are in an emergency. So bottom line, if you are lost and then the clouds break - getting anything on paper is good, you can use it as a first approximation and then try again as able. Hope that helps!
Thanks for the videos. It's really helpful.
Hi Chris, I see where the nautical almanac shows the moon’s meridian passage. I assume you can use this for a daytime moon sight similar to a noon sun sight. Is that’s so, why have I not heard anyone talk about it. One could get the equivalent of noon sight in the morning or the afternoon depending on when a daytime moon culminates.. On another issue, I have recently been looking at the air almanac. It seem simpler-less interpolation, no hp’s to deal with (with a simpler moon corrections on each page}, no v or d values to deal with, and no need to deal with 0.1 of miles which is likely beyond most person’s ability to accurately determine in the firs place. Just wondering about your thoughts on these issues. Thanks much.
great course! don't really get where you found the 3nd correction
That was all for sea level navigation. Can one do this on the Great Lakes, which are not at sea level? The altitude of these lakes are different and changes due to season and weather. How can we account for this varying water level?
It works for large lakes where there is a horizon to get the level. If the shore is visible, then there is no accurate level reference line. You can even use a bowl of liquid (water, oil, mercury) as overland explorers used to do.
@@karhukivi If you do the bowl of water trick, you need to divide the measured angle by two after correcting for index error. In this case, there is no correction for limb choice, as you just superimpose the two identical images upon each other. Most sextants will not have enough range of adjustment to measure an object that is much more than 65 degrees above the horizon due to the doubled angle of measurement, so summer time noon sights in lower latitudes become unavailable, but accuracy with this method tends to be excellent. It often helps to put a piece of glass or saran wrap over the bowl to keep wind from disturbing the water's surface.
@@youtubeleavemealone I use a Davis "artificial horizon" which has sun filters that also keep the wind out. Instead of water I use propylene glycol which does not leave condensation on the filters and is somewhat more viscous than water. The Davis Mk25 sextant can superimpose images but otherwise it is easier to use upper or lower limbs, especially for the moon when it is only partially illuminated. Depending on one's latitude, summertime noon sights can be beyond the range of the sextant, but I use morning and afternoon sights to get a position and the angle is usually within range.
@@karhukivi The Davis artificial horizon is nice for a few reasons. It uses angled glass, which prevents you from confusing glass reflection with water reflection. It comes with shaded lenses so that you don't blind yourself looking for the sun's reflection & it packs up small for easy back packing. I manage to superimpose images on a split screen MK15 as well as a MK 25. For me it works well. Personal preferences may vary. On a genuine horizon, I do use the lower limb of the sun, as is traditional.
@@youtubeleavemealone Yes, it is a neat device. I use propylene glycol, the liquid base used in vaping liquids. It's non-toxic, has a high boiling point and a low freezing point, as well as being somewhat viscous, so it's better than water. It is soluble in water too, so easy to clean. a 1L bottle cost me $10 from a vaping supplies shop.
Navigator Chris has outlined the proceedure for Apparent Altitude correction of Moon sights. He advises to spend some time with the tables.
There is a useful but slower paced explanation for this task starting at moment 09:02 on Andy Howe's channel "The Nav Station" Episode #14.
If i can get the link typed in correctly and if the UT police leave things in peace !!
ua-cam.com/video/hrmqS2-p85Q/v-deo.html
Hope that helps anyone needs an extra input on this correction. Cheers . John R.
Many thanks for making this excellent series - I hope it inspires lots of sailors to turn away from their GPS sets and start using a sextant. I wrote my book 'Sextant' with exactly the same aim, though it's not a 'how to' guide. It's part personal memoir, part history and part science - with many examples of great voyages guided by the stars, from Bougainville and Cook to Slocum and Worsley. In case you want to read it, it's published by William Morrow in the US and William Collins in the UK. There is also a new Italian translation and a German one is due out in 2015. Good sailing! By the way, I'm promoting these videos as best I can:@sextantnav as well as 'sextantbook' on Facebook and Tumblr.
I read your book as a pandemic diversion; nice job! I hadn’t fully understood that the lunar distance method emerged around the same time as the chronometer, and how these tools complemented one another for so long.
Wesley Burghardt Many thanks Wesley. I’m glad you enjoyed it! You might possibly also be interested in my latest book, SUPERNAVIGATORS which is about the science of animal navigation. More details on my website davidbarrieauthor.org. Best wishes David